actually test always_zero hasher

run some tests with always_zero hasher
switch to petgraph 0.8.1 now that my PR was merged and released to crates.io
2025-04-09 21:11:09 -07:00 · 2025-04-09 21:03:57 -07:00 · 2025-04-09 20:48:40 -07:00 · 2025-04-09 20:33:21 -07:00 · 2025-04-09 20:27:22 -07:00 · 2025-04-09 20:23:19 -07:00
139 changed files with 67558 additions and 15167 deletions
--- a/.forgejo/workflows/deps.yml
+++ b/.forgejo/workflows/deps.yml
@ -0,0 +1,77 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# See Notices.txt for copyright information
+on:
+  workflow_call:
+    outputs:
+      cache-primary-key:
+        value: ${{ jobs.deps.outputs.cache-primary-key }}
+
+jobs:
+  deps:
+    runs-on: debian-12
+    outputs:
+      cache-primary-key: ${{ steps.restore-deps.outputs.cache-primary-key }}
+    steps:
+      - uses: https://git.libre-chip.org/mirrors/checkout@v3
+        with:
+          fetch-depth: 0
+      - uses: https://git.libre-chip.org/mirrors/cache/restore@v3
+        id: restore-deps
+        with:
+          path: deps
+          key: ${{ github.repository }}-deps-${{ runner.os }}-${{ hashFiles('.forgejo/workflows/deps.yml') }}
+          lookup-only: true
+      - name: Install Apt packages
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        run: |
+          apt-get update -qq
+          apt-get install -qq \
+            bison \
+            build-essential \
+            ccache \
+            clang \
+            cvc5 \
+            flex \
+            gawk \
+            g++ \
+            git \
+            libboost-filesystem-dev \
+            libboost-python-dev \
+            libboost-system-dev \
+            libffi-dev \
+            libreadline-dev \
+            lld \
+            pkg-config \
+            python3 \
+            python3-click \
+            tcl-dev \
+            zlib1g-dev
+      - name: Install Firtool
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        run: |
+          mkdir -p deps
+          wget -O deps/firrtl.tar.gz https://github.com/llvm/circt/releases/download/firtool-1.86.0/firrtl-bin-linux-x64.tar.gz
+          sha256sum -c - <<<'bf6f4ab18ae76f135c944efbd81e25391c31c1bd0617c58ab0592640abefee14  deps/firrtl.tar.gz'
+          tar -C deps -xvaf deps/firrtl.tar.gz
+          rm -rf deps/firtool
+          mv deps/firtool-1.86.0 deps/firtool
+      - name: Get SymbiYosys
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        run: |
+          git clone --depth=1 --branch=yosys-0.45 https://git.libre-chip.org/mirrors/sby deps/sby
+      - name: Build Z3
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        run: |
+          git clone --depth=1 --recursive --branch=z3-4.13.3 https://git.libre-chip.org/mirrors/z3 deps/z3
+          (cd deps/z3; PYTHON=python3 ./configure --prefix=/usr/local)
+          make -C deps/z3/build -j"$(nproc)"
+      - name: Build Yosys
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        run: |
+          git clone --depth=1 --recursive --branch=0.45 https://git.libre-chip.org/mirrors/yosys deps/yosys
+          make -C deps/yosys -j"$(nproc)"
+      - uses: https://git.libre-chip.org/mirrors/cache/save@v3
+        if: steps.restore-deps.outputs.cache-hit != 'true'
+        with:
+          path: deps
+          key: ${{ steps.restore-deps.outputs.cache-primary-key }}
--- a/.forgejo/workflows/test.yml
+++ b/.forgejo/workflows/test.yml
@ -1,19 +1,62 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# See Notices.txt for copyright information
 on: [push, pull_request]

 jobs:
+  deps:
+    uses: ./.forgejo/workflows/deps.yml
  test:
    runs-on: debian-12
+    needs: deps
    steps:
-      - uses: https://code.forgejo.org/actions/checkout@v3
+      - uses: https://git.libre-chip.org/mirrors/checkout@v3
        with:
          fetch-depth: 0
      - run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain 1.79.0
+          scripts/check-copyright.sh
+      - run: |
+          apt-get update -qq
+          apt-get install -qq \
+            bison \
+            build-essential \
+            ccache \
+            clang \
+            cvc5 \
+            flex \
+            gawk \
+            git \
+            libboost-filesystem-dev \
+            libboost-python-dev \
+            libboost-system-dev \
+            libffi-dev \
+            libreadline-dev \
+            lld \
+            pkg-config \
+            python3 \
+            python3-click \
+            tcl-dev \
+            z3 \
+            zlib1g-dev
+      - run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain 1.82.0
          source "$HOME/.cargo/env"
          echo "$PATH" >> "$GITHUB_PATH"
-      - uses: https://github.com/Swatinem/rust-cache@v2
+      - uses: https://git.libre-chip.org/mirrors/cache/restore@v3
+        with:
+          path: deps
+          key: ${{ needs.deps.outputs.cache-primary-key }}
+          fail-on-cache-miss: true
+      - run: |
+          make -C deps/z3/build install
+          make -C deps/sby install
+          make -C deps/yosys install
+          export PATH="$(realpath deps/firtool/bin):$PATH"
+          echo "$PATH" >> "$GITHUB_PATH"
+      - uses: https://git.libre-chip.org/mirrors/rust-cache@v2
        with:
          save-if: ${{ github.ref == 'refs/heads/master' }}
      - run: cargo test
-      - run: cargo test --features=unstable-doc
+      - run: cargo build --tests --features=unstable-doc
+      - run: cargo test --doc --features=unstable-doc
      - run: cargo doc --features=unstable-doc
+      - run: FAYALITE_TEST_HASHER=always_zero cargo test --test=module --features=unstable-doc,unstable-test-hasher
--- a/.gitignore
+++ b/.gitignore
@ -1,2 +1,4 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# See Notices.txt for copyright information
 /target
-.vscode
+.vscode
--- a/Cargo.lock
+++ b/Cargo.lock
@ -2,18 +2,6 @@
 # It is not intended for manual editing.
 version = 3

-[[package]]
-name = "ahash"
-version = "0.8.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77c3a9648d43b9cd48db467b3f87fdd6e146bcc88ab0180006cef2179fe11d01"
-dependencies = [
- "cfg-if",
- "once_cell",
- "version_check",
- "zerocopy",
-]
-
 [[package]]
 name = "allocator-api2"
 version = "0.2.16"
@ -56,7 +44,7 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ad186efb764318d35165f1758e7dcef3b10628e26d41a44bc5550652e6804391"
 dependencies = [
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

 [[package]]
@ -66,9 +54,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "61a38449feb7068f52bb06c12759005cf459ee52bb4adc1d5a7c4322d716fb19"
 dependencies = [
 "anstyle",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

+[[package]]
+name = "arrayref"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76a2e8124351fda1ef8aaaa3bbd7ebbcb486bbcd4225aca0aa0d84bb2db8fecb"
+
+[[package]]
+name = "arrayvec"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c02d123df017efcdfbd739ef81735b36c5ba83ec3c59c80a9d7ecc718f92e50"
+
 [[package]]
 name = "autocfg"
 version = "1.1.0"
@ -109,6 +109,20 @@ dependencies = [
 "wyz",
 ]

+[[package]]
+name = "blake3"
+version = "1.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d82033247fd8e890df8f740e407ad4d038debb9eb1f40533fffb32e7d17dc6f7"
+dependencies = [
+ "arrayref",
+ "arrayvec",
+ "cc",
+ "cfg-if",
+ "constant_time_eq",
+ "serde",
+]
+
 [[package]]
 name = "block-buffer"
 version = "0.10.4"
@ -118,6 +132,15 @@ dependencies = [
 "generic-array",
 ]

+[[package]]
+name = "cc"
+version = "1.1.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e80e3b6a3ab07840e1cae9b0666a63970dc28e8ed5ffbcdacbfc760c281bfc1"
+dependencies = [
+ "shlex",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@ -170,6 +193,12 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b6a852b24ab71dffc585bcb46eaf7959d175cb865a7152e35b348d1b2960422"

+[[package]]
+name = "constant_time_eq"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c74b8349d32d297c9134b8c88677813a227df8f779daa29bfc29c183fe3dca6"
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.12"
@ -189,6 +218,27 @@ dependencies = [
 "typenum",
 ]

+[[package]]
+name = "ctor"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "edb49164822f3ee45b17acd4a208cfc1251410cf0cad9a833234c9890774dd9f"
+dependencies = [
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "derive_destructure2"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64b697ac90ff296f0fc031ee5a61c7ac31fb9fff50e3fb32873b09223613fc0c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@ -218,7 +268,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a258e46cdc063eb8519c00b9fc845fc47bcfca4130e2f08e88665ceda8474245"
 dependencies = [
 "libc",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

 [[package]]
@ -239,32 +289,39 @@ checksum = "25cbce373ec4653f1a01a31e8a5e5ec0c622dc27ff9c4e6606eefef5cbbed4a5"

 [[package]]
 name = "fayalite"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
 "bitvec",
+ "blake3",
 "clap",
+ "ctor",
 "eyre",
 "fayalite-proc-macros",
 "fayalite-visit-gen",
 "hashbrown",
+ "jobslot",
 "num-bigint",
 "num-traits",
+ "os_pipe",
+ "petgraph",
 "serde",
 "serde_json",
+ "tempfile",
 "trybuild",
+ "vec_map",
 "which",
 ]

 [[package]]
 name = "fayalite-proc-macros"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
 "fayalite-proc-macros-impl",
 ]

 [[package]]
 name = "fayalite-proc-macros-impl"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
 "base16ct",
 "num-bigint",
@ -278,7 +335,7 @@ dependencies = [

 [[package]]
 name = "fayalite-visit-gen"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
 "indexmap",
 "prettyplease",
@ -290,6 +347,18 @@ dependencies = [
 "thiserror",
 ]

+[[package]]
+name = "fixedbitset"
+version = "0.5.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d674e81391d1e1ab681a28d99df07927c6d4aa5b027d7da16ba32d1d21ecd99"
+
+[[package]]
+name = "foldhash"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
+
 [[package]]
 name = "funty"
 version = "2.0.0"
@ -306,6 +375,17 @@ dependencies = [
 "version_check",
 ]

+[[package]]
+name = "getrandom"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94b22e06ecb0110981051723910cbf0b5f5e09a2062dd7663334ee79a9d1286c"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "glob"
 version = "0.3.1"
@ -314,12 +394,13 @@ checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"

 [[package]]
 name = "hashbrown"
-version = "0.14.3"
+version = "0.15.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
+checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
 dependencies = [
- "ahash",
 "allocator-api2",
+ "equivalent",
+ "foldhash",
 ]

 [[package]]
@ -334,7 +415,7 @@ version = "0.5.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e3d1354bf6b7235cb4a0576c2619fd4ed18183f689b12b006a0ee7329eeff9a5"
 dependencies = [
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

 [[package]]
@ -345,9 +426,9 @@ checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"

 [[package]]
 name = "indexmap"
-version = "2.2.6"
+version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "168fb715dda47215e360912c096649d23d58bf392ac62f73919e831745e40f26"
+checksum = "cea70ddb795996207ad57735b50c5982d8844f38ba9ee5f1aedcfb708a2aa11e"
 dependencies = [
 "equivalent",
 "hashbrown",
@ -366,6 +447,20 @@ version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b1a46d1a171d865aa5f83f92695765caa047a9b4cbae2cbf37dbd613a793fd4c"

+[[package]]
+name = "jobslot"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe10868679d7a24c2c67d862d0e64a342ce9aef7cdde9ce8019bd35d353d458d"
+dependencies = [
+ "cfg-if",
+ "derive_destructure2",
+ "getrandom",
+ "libc",
+ "scopeguard",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.153"
@ -380,11 +475,10 @@ checksum = "01cda141df6706de531b6c46c3a33ecca755538219bd484262fa09410c13539c"

 [[package]]
 name = "num-bigint"
-version = "0.4.4"
+version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
+checksum = "a5e44f723f1133c9deac646763579fdb3ac745e418f2a7af9cd0c431da1f20b9"
 dependencies = [
- "autocfg",
 "num-integer",
 "num-traits",
 ]
@ -413,6 +507,28 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"

+[[package]]
+name = "os_pipe"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ffd2b0a5634335b135d5728d84c5e0fd726954b87111f7506a61c502280d982"
+dependencies = [
+ "libc",
+ "windows-sys 0.59.0",
+]
+
+[[package]]
+name = "petgraph"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a98c6720655620a521dcc722d0ad66cd8afd5d86e34a89ef691c50b7b24de06"
+dependencies = [
+ "fixedbitset",
+ "hashbrown",
+ "indexmap",
+ "serde",
+]
+
 [[package]]
 name = "prettyplease"
 version = "0.2.20"
@ -425,9 +541,9 @@ dependencies = [

 [[package]]
 name = "proc-macro2"
-version = "1.0.83"
+version = "1.0.92"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b33eb56c327dec362a9e55b3ad14f9d2f0904fb5a5b03b513ab5465399e9f43"
+checksum = "37d3544b3f2748c54e147655edb5025752e2303145b5aefb3c3ea2c78b973bb0"
 dependencies = [
 "unicode-ident",
 ]
@ -457,7 +573,7 @@ dependencies = [
 "errno",
 "libc",
 "linux-raw-sys",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

 [[package]]
@ -466,6 +582,12 @@ version = "1.0.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e86697c916019a8588c99b5fac3cead74ec0b4b819707a682fd4d23fa0ce1ba1"

+[[package]]
+name = "scopeguard"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
+
 [[package]]
 name = "serde"
 version = "1.0.202"
@ -509,6 +631,12 @@ dependencies = [
 "digest",
 ]

+[[package]]
+name = "shlex"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
+
 [[package]]
 name = "strsim"
 version = "0.11.1"
@ -517,9 +645,9 @@ checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"

 [[package]]
 name = "syn"
-version = "2.0.66"
+version = "2.0.93"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c42f3f41a2de00b01c0aaad383c5a45241efc8b2d1eda5661812fda5f3cdcff5"
+checksum = "9c786062daee0d6db1132800e623df74274a0a87322d8e183338e01b3d98d058"
 dependencies = [
 "proc-macro2",
 "quote",
@ -541,7 +669,7 @@ dependencies = [
 "cfg-if",
 "fastrand",
 "rustix",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]

 [[package]]
@ -606,12 +734,24 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"

+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
 [[package]]
 name = "version_check"
 version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"

+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+
 [[package]]
 name = "which"
 version = "6.0.1"
@ -665,14 +805,24 @@ dependencies = [
 ]

 [[package]]
-name = "windows-targets"
-version = "0.52.4"
+name = "windows-sys"
+version = "0.59.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7dd37b7e5ab9018759f893a1952c9420d060016fc19a472b4bb20d1bdd694d1b"
+checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
 dependencies = [
 "windows_aarch64_gnullvm",
 "windows_aarch64_msvc",
 "windows_i686_gnu",
+ "windows_i686_gnullvm",
 "windows_i686_msvc",
 "windows_x86_64_gnu",
 "windows_x86_64_gnullvm",
@ -681,45 +831,51 @@ dependencies = [

 [[package]]
 name = "windows_aarch64_gnullvm"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bcf46cf4c365c6f2d1cc93ce535f2c8b244591df96ceee75d8e83deb70a9cac9"
+checksum = "32a4622180e7a0ec044bb555404c800bc9fd9ec262ec147edd5989ccd0c02cd3"

 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da9f259dd3bcf6990b55bffd094c4f7235817ba4ceebde8e6d11cd0c5633b675"
+checksum = "09ec2a7bb152e2252b53fa7803150007879548bc709c039df7627cabbd05d469"

 [[package]]
 name = "windows_i686_gnu"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b474d8268f99e0995f25b9f095bc7434632601028cf86590aea5c8a5cb7801d3"
+checksum = "8e9b5ad5ab802e97eb8e295ac6720e509ee4c243f69d781394014ebfe8bbfa0b"
+
+[[package]]
+name = "windows_i686_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0eee52d38c090b3caa76c563b86c3a4bd71ef1a819287c19d586d7334ae8ed66"

 [[package]]
 name = "windows_i686_msvc"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1515e9a29e5bed743cb4415a9ecf5dfca648ce85ee42e15873c3cd8610ff8e02"
+checksum = "240948bc05c5e7c6dabba28bf89d89ffce3e303022809e73deaefe4f6ec56c66"

 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5eee091590e89cc02ad514ffe3ead9eb6b660aedca2183455434b93546371a03"
+checksum = "147a5c80aabfbf0c7d901cb5895d1de30ef2907eb21fbbab29ca94c5b08b1a78"

 [[package]]
 name = "windows_x86_64_gnullvm"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77ca79f2451b49fa9e2af39f0747fe999fcda4f5e241b2898624dca97a1f2177"
+checksum = "24d5b23dc417412679681396f2b49f3de8c1473deb516bd34410872eff51ed0d"

 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.52.4"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "32b752e52a2da0ddfbdbcc6fceadfeede4c939ed16d13e648833a61dfb611ed8"
+checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"

 [[package]]
 name = "winsafe"
@ -735,23 +891,3 @@ checksum = "05f360fc0b24296329c78fda852a1e9ae82de9cf7b27dae4b7f62f118f77b9ed"
 dependencies = [
 "tap",
 ]
-
-[[package]]
-name = "zerocopy"
-version = "0.7.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74d4d3961e53fa4c9a25a8637fc2bfaf2595b3d3ae34875568a5cf64787716be"
-dependencies = [
- "zerocopy-derive",
-]
-
-[[package]]
-name = "zerocopy-derive"
-version = "0.7.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ce1b18ccd8e73a9321186f97e46f9f04b778851177567b1975109d26a08d2a6"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
--- a/Cargo.toml
+++ b/Cargo.toml
@ -5,31 +5,40 @@ resolver = "2"
 members = ["crates/*"]

 [workspace.package]
-version = "0.2.0"
+version = "0.3.0"
 license = "LGPL-3.0-or-later"
 edition = "2021"
 repository = "https://git.libre-chip.org/libre-chip/fayalite"
 keywords = ["hdl", "hardware", "semiconductors", "firrtl", "fpga"]
 categories = ["simulation", "development-tools", "compilers"]
-rust-version = "1.79"
+rust-version = "1.82.0"

 [workspace.dependencies]
-fayalite-proc-macros = { version = "=0.2.0", path = "crates/fayalite-proc-macros" }
-fayalite-proc-macros-impl = { version = "=0.2.0", path = "crates/fayalite-proc-macros-impl" }
-fayalite-visit-gen = { version = "=0.2.0", path = "crates/fayalite-visit-gen" }
+fayalite-proc-macros = { version = "=0.3.0", path = "crates/fayalite-proc-macros" }
+fayalite-proc-macros-impl = { version = "=0.3.0", path = "crates/fayalite-proc-macros-impl" }
+fayalite-visit-gen = { version = "=0.3.0", path = "crates/fayalite-visit-gen" }
 base16ct = "0.2.0"
 bitvec = { version = "1.0.1", features = ["serde"] }
-hashbrown = "0.14.3"
-indexmap = { version = "2.2.6", features = ["serde"] }
-num-bigint = "0.4.4"
+blake3 = { version = "1.5.4", features = ["serde"] }
+clap = { version = "4.5.9", features = ["derive", "env", "string"] }
+ctor = "0.2.8"
+eyre = "0.6.12"
+hashbrown = "0.15.2"
+indexmap = { version = "2.5.0", features = ["serde"] }
+jobslot = "0.2.19"
+num-bigint = "0.4.6"
 num-traits = "0.2.16"
+os_pipe = "1.2.1"
+petgraph = "0.8.1"
 prettyplease = "0.2.20"
 proc-macro2 = "1.0.83"
 quote = "1.0.36"
 serde = { version = "1.0.202", features = ["derive"] }
 serde_json = { version = "1.0.117", features = ["preserve_order"] }
 sha2 = "0.10.8"
-syn = { version = "2.0.66", features = ["full", "fold", "visit", "extra-traits"] }
+syn = { version = "2.0.93", features = ["full", "fold", "visit", "extra-traits"] }
 tempfile = "3.10.1"
 thiserror = "1.0.61"
 trybuild = "1.0"
+vec_map = "0.8.2"
+which = "6.0.1"
--- a/README.md
+++ b/README.md
@ -1,3 +1,7 @@
+<!--
+SPDX-License-Identifier: LGPL-3.0-or-later
+See Notices.txt for copyright information
+-->
 # Fayalite

 Fayalite is a library for designing digital hardware -- a hardware description language (HDL) embedded in the Rust programming language. Fayalite's semantics are based on [FIRRTL] as interpreted by [LLVM CIRCT](https://circt.llvm.org/docs/Dialects/FIRRTL/FIRRTLAnnotations/).
--- a/crates/fayalite-proc-macros-impl/Cargo.toml
+++ b/crates/fayalite-proc-macros-impl/Cargo.toml
@ -13,11 +13,11 @@ rust-version.workspace = true
 version.workspace = true

 [dependencies]
-base16ct = { workspace = true }
-num-bigint = { workspace = true }
-prettyplease = { workspace = true }
-proc-macro2 = { workspace = true }
-quote = { workspace = true }
-sha2 = { workspace = true }
-syn = { workspace = true }
-tempfile = { workspace = true }
+base16ct.workspace = true
+num-bigint.workspace = true
+prettyplease.workspace = true
+proc-macro2.workspace = true
+quote.workspace = true
+sha2.workspace = true
+syn.workspace = true
+tempfile.workspace = true
--- a/crates/fayalite-proc-macros-impl/src/fold.rs
+++ b/crates/fayalite-proc-macros-impl/src/fold.rs
@ -220,29 +220,36 @@ forward_fold!(syn::ExprArray => fold_expr_array);
 forward_fold!(syn::ExprCall => fold_expr_call);
 forward_fold!(syn::ExprIf => fold_expr_if);
 forward_fold!(syn::ExprMatch => fold_expr_match);
+forward_fold!(syn::ExprMethodCall => fold_expr_method_call);
 forward_fold!(syn::ExprPath => fold_expr_path);
 forward_fold!(syn::ExprRepeat => fold_expr_repeat);
 forward_fold!(syn::ExprStruct => fold_expr_struct);
 forward_fold!(syn::ExprTuple => fold_expr_tuple);
+forward_fold!(syn::FieldPat => fold_field_pat);
 forward_fold!(syn::Ident => fold_ident);
 forward_fold!(syn::Member => fold_member);
 forward_fold!(syn::Path => fold_path);
 forward_fold!(syn::Type => fold_type);
 forward_fold!(syn::TypePath => fold_type_path);
 forward_fold!(syn::WherePredicate => fold_where_predicate);
+no_op_fold!(proc_macro2::Span);
 no_op_fold!(syn::parse::Nothing);
 no_op_fold!(syn::token::Brace);
 no_op_fold!(syn::token::Bracket);
+no_op_fold!(syn::token::Group);
 no_op_fold!(syn::token::Paren);
 no_op_fold!(syn::Token![_]);
 no_op_fold!(syn::Token![,]);
 no_op_fold!(syn::Token![;]);
 no_op_fold!(syn::Token![:]);
+no_op_fold!(syn::Token![::]);
 no_op_fold!(syn::Token![..]);
 no_op_fold!(syn::Token![.]);
 no_op_fold!(syn::Token![#]);
+no_op_fold!(syn::Token![<]);
 no_op_fold!(syn::Token![=]);
 no_op_fold!(syn::Token![=>]);
+no_op_fold!(syn::Token![>]);
 no_op_fold!(syn::Token![|]);
 no_op_fold!(syn::Token![enum]);
 no_op_fold!(syn::Token![extern]);
@ -251,3 +258,4 @@ no_op_fold!(syn::Token![mut]);
 no_op_fold!(syn::Token![static]);
 no_op_fold!(syn::Token![struct]);
 no_op_fold!(syn::Token![where]);
+no_op_fold!(usize);
--- a/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
--- a/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
--- a/crates/fayalite-proc-macros-impl/src/hdl_type_alias.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_type_alias.rs
@ -0,0 +1,138 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use crate::{
+    hdl_type_common::{
+        get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics, ParsedType,
+        TypesParser,
+    },
+    kw, Errors, HdlAttr,
+};
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use syn::{parse_quote_spanned, Attribute, Generics, Ident, ItemType, Token, Type, Visibility};
+
+#[derive(Clone, Debug)]
+pub(crate) struct ParsedTypeAlias {
+    pub(crate) attrs: Vec<Attribute>,
+    pub(crate) options: HdlAttr<ItemOptions, kw::hdl>,
+    pub(crate) vis: Visibility,
+    pub(crate) type_token: Token![type],
+    pub(crate) ident: Ident,
+    pub(crate) generics: MaybeParsed<ParsedGenerics, Generics>,
+    pub(crate) eq_token: Token![=],
+    pub(crate) ty: MaybeParsed<ParsedType, Type>,
+    pub(crate) semi_token: Token![;],
+}
+
+impl ParsedTypeAlias {
+    fn parse(item: ItemType) -> syn::Result<Self> {
+        let ItemType {
+            mut attrs,
+            vis,
+            type_token,
+            ident,
+            mut generics,
+            eq_token,
+            ty,
+            semi_token,
+        } = item;
+        let mut errors = Errors::new();
+        let mut options = errors
+            .unwrap_or_default(HdlAttr::<ItemOptions, kw::hdl>::parse_and_take_attr(
+                &mut attrs,
+            ))
+            .unwrap_or_default();
+        errors.ok(options.body.validate());
+        let ItemOptions {
+            outline_generated: _,
+            target: _,
+            custom_bounds,
+            no_static,
+            no_runtime_generics: _,
+            cmp_eq,
+        } = options.body;
+        if let Some((no_static,)) = no_static {
+            errors.error(no_static, "no_static is not valid on type aliases");
+        }
+        if let Some((cmp_eq,)) = cmp_eq {
+            errors.error(cmp_eq, "cmp_eq is not valid on type aliases");
+        }
+        let generics = if custom_bounds.is_some() {
+            MaybeParsed::Unrecognized(generics)
+        } else if let Some(generics) = errors.ok(ParsedGenerics::parse(&mut generics)) {
+            MaybeParsed::Parsed(generics)
+        } else {
+            MaybeParsed::Unrecognized(generics)
+        };
+        let ty = TypesParser::maybe_run(generics.as_ref(), *ty, &mut errors);
+        errors.finish()?;
+        Ok(Self {
+            attrs,
+            options,
+            vis,
+            type_token,
+            ident,
+            generics,
+            eq_token,
+            ty,
+            semi_token,
+        })
+    }
+}
+
+impl ToTokens for ParsedTypeAlias {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attrs,
+            options,
+            vis,
+            type_token,
+            ident,
+            generics,
+            eq_token,
+            ty,
+            semi_token,
+        } = self;
+        let ItemOptions {
+            outline_generated: _,
+            target,
+            custom_bounds: _,
+            no_static: _,
+            no_runtime_generics,
+            cmp_eq: _,
+        } = &options.body;
+        let target = get_target(target, ident);
+        let mut type_attrs = attrs.clone();
+        type_attrs.push(parse_quote_spanned! {ident.span()=>
+            #[allow(type_alias_bounds)]
+        });
+        ItemType {
+            attrs: type_attrs,
+            vis: vis.clone(),
+            type_token: *type_token,
+            ident: ident.clone(),
+            generics: generics.into(),
+            eq_token: *eq_token,
+            ty: Box::new(ty.clone().into()),
+            semi_token: *semi_token,
+        }
+        .to_tokens(tokens);
+        if let (MaybeParsed::Parsed(generics), MaybeParsed::Parsed(ty), None) =
+            (generics, ty, no_runtime_generics)
+        {
+            generics.make_runtime_generics(tokens, vis, ident, &target, |context| {
+                ty.make_hdl_type_expr(context)
+            })
+        }
+    }
+}
+
+pub(crate) fn hdl_type_alias_impl(item: ItemType) -> syn::Result<TokenStream> {
+    let item = ParsedTypeAlias::parse(item)?;
+    let outline_generated = item.options.body.outline_generated;
+    let mut contents = item.to_token_stream();
+    if outline_generated.is_some() {
+        contents = crate::outline_generated(contents, "hdl-type-alias-");
+    }
+    Ok(contents)
+}
--- a/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs
--- a/crates/fayalite-proc-macros-impl/src/lib.rs
+++ b/crates/fayalite-proc-macros-impl/src/lib.rs
@ -3,25 +3,46 @@
 #![cfg_attr(test, recursion_limit = "512")]
 use proc_macro2::{Span, TokenStream};
 use quote::{quote, ToTokens};
-use std::io::{ErrorKind, Write};
+use std::{
+    collections::{hash_map::Entry, HashMap},
+    io::{ErrorKind, Write},
+};
 use syn::{
-    bracketed, parenthesized,
+    bracketed,
+    ext::IdentExt,
+    parenthesized,
    parse::{Parse, ParseStream, Parser},
    parse_quote,
-    punctuated::Pair,
-    AttrStyle, Attribute, Error, Item, Token,
+    punctuated::{Pair, Punctuated},
+    spanned::Spanned,
+    token::{Bracket, Paren},
+    AttrStyle, Attribute, Error, Ident, Item, ItemFn, LitBool, LitStr, Meta, Token,
 };

 mod fold;
+mod hdl_bundle;
+mod hdl_enum;
+mod hdl_type_alias;
+mod hdl_type_common;
 mod module;
-mod value_derive_common;
-mod value_derive_enum;
-mod value_derive_struct;
+mod process_cfg;
+
+pub(crate) trait CustomToken:
+    Copy
+    + Spanned
+    + ToTokens
+    + std::fmt::Debug
+    + Eq
+    + std::hash::Hash
+    + Default
+    + quote::IdentFragment
+    + Parse
+{
+    const IDENT_STR: &'static str;
+}

 mod kw {
-    pub(crate) use syn::token::{
-        Enum as enum_, Extern as extern_, Static as static_, Struct as struct_, Where as where_,
-    };
+    pub(crate) use syn::token::Extern as extern_;

    macro_rules! custom_keyword {
        ($kw:ident) => {
@ -38,13 +59,26 @@ mod kw {
            }

            crate::fold::no_op_fold!($kw);
+
+            impl crate::CustomToken for $kw {
+                const IDENT_STR: &'static str = stringify!($kw);
+            }
        };
    }

+    custom_keyword!(__evaluated_cfgs);
+    custom_keyword!(all);
+    custom_keyword!(any);
+    custom_keyword!(cfg);
+    custom_keyword!(cfg_attr);
    custom_keyword!(clock_domain);
+    custom_keyword!(cmp_eq);
    custom_keyword!(connect_inexact);
+    custom_keyword!(custom_bounds);
    custom_keyword!(flip);
    custom_keyword!(hdl);
+    custom_keyword!(hdl_module);
+    custom_keyword!(incomplete_wire);
    custom_keyword!(input);
    custom_keyword!(instance);
    custom_keyword!(m);
@ -52,11 +86,14 @@ mod kw {
    custom_keyword!(memory_array);
    custom_keyword!(memory_with_init);
    custom_keyword!(no_reset);
+    custom_keyword!(no_runtime_generics);
+    custom_keyword!(no_static);
+    custom_keyword!(not);
    custom_keyword!(outline_generated);
    custom_keyword!(output);
    custom_keyword!(reg_builder);
    custom_keyword!(reset);
-    custom_keyword!(reset_default);
+    custom_keyword!(sim);
    custom_keyword!(skip);
    custom_keyword!(target);
    custom_keyword!(wire);
@ -65,34 +102,34 @@ mod kw {
 type Pound = Token![#]; // work around https://github.com/rust-lang/rust/issues/50676

 #[derive(Clone, Debug)]
-pub(crate) struct HdlAttr<T> {
+pub(crate) struct HdlAttr<T, KW> {
    pub(crate) pound_token: Pound,
    pub(crate) style: AttrStyle,
    pub(crate) bracket_token: syn::token::Bracket,
-    pub(crate) hdl: kw::hdl,
+    pub(crate) kw: KW,
    pub(crate) paren_token: Option<syn::token::Paren>,
    pub(crate) body: T,
 }

 crate::fold::impl_fold! {
-    struct HdlAttr<T,> {
+    struct HdlAttr<T, KW,> {
        pound_token: Pound,
        style: AttrStyle,
        bracket_token: syn::token::Bracket,
-        hdl: kw::hdl,
+        kw: KW,
        paren_token: Option<syn::token::Paren>,
        body: T,
    }
 }

 #[allow(dead_code)]
-impl<T> HdlAttr<T> {
-    pub(crate) fn split_body(self) -> (HdlAttr<()>, T) {
+impl<T, KW> HdlAttr<T, KW> {
+    pub(crate) fn split_body(self) -> (HdlAttr<(), KW>, T) {
        let Self {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body,
        } = self;
@ -101,19 +138,19 @@ impl<T> HdlAttr<T> {
                pound_token,
                style,
                bracket_token,
-                hdl,
+                kw,
                paren_token,
                body: (),
            },
            body,
        )
    }
-    pub(crate) fn replace_body<T2>(self, body: T2) -> HdlAttr<T2> {
+    pub(crate) fn replace_body<T2>(self, body: T2) -> HdlAttr<T2, KW> {
        let Self {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body: _,
        } = self;
@ -121,17 +158,20 @@ impl<T> HdlAttr<T> {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body,
        }
    }
-    pub(crate) fn as_ref(&self) -> HdlAttr<&T> {
+    pub(crate) fn as_ref(&self) -> HdlAttr<&T, KW>
+    where
+        KW: Clone,
+    {
        let Self {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            ref kw,
            paren_token,
            ref body,
        } = *self;
@ -139,17 +179,20 @@ impl<T> HdlAttr<T> {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw: kw.clone(),
            paren_token,
            body,
        }
    }
-    pub(crate) fn try_map<R, E, F: FnOnce(T) -> Result<R, E>>(self, f: F) -> Result<HdlAttr<R>, E> {
+    pub(crate) fn try_map<R, E, F: FnOnce(T) -> Result<R, E>>(
+        self,
+        f: F,
+    ) -> Result<HdlAttr<R, KW>, E> {
        let Self {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body,
        } = self;
@ -157,17 +200,17 @@ impl<T> HdlAttr<T> {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body: f(body)?,
        })
    }
-    pub(crate) fn map<R, F: FnOnce(T) -> R>(self, f: F) -> HdlAttr<R> {
+    pub(crate) fn map<R, F: FnOnce(T) -> R>(self, f: F) -> HdlAttr<R, KW> {
        let Self {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body,
        } = self;
@ -175,7 +218,7 @@ impl<T> HdlAttr<T> {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body: f(body),
        }
@ -183,31 +226,32 @@ impl<T> HdlAttr<T> {
    fn to_attr(&self) -> Attribute
    where
        T: ToTokens,
+        KW: ToTokens,
    {
        parse_quote! { #self }
    }
 }

-impl<T: Default> Default for HdlAttr<T> {
+impl<T: Default, KW: Default> Default for HdlAttr<T, KW> {
    fn default() -> Self {
        T::default().into()
    }
 }

-impl<T> From<T> for HdlAttr<T> {
+impl<T, KW: Default> From<T> for HdlAttr<T, KW> {
    fn from(body: T) -> Self {
        HdlAttr {
            pound_token: Default::default(),
            style: AttrStyle::Outer,
            bracket_token: Default::default(),
-            hdl: Default::default(),
+            kw: Default::default(),
            paren_token: Default::default(),
            body,
        }
    }
 }

-impl<T: ToTokens> ToTokens for HdlAttr<T> {
+impl<T: ToTokens, KW: ToTokens + Spanned> ToTokens for HdlAttr<T, KW> {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        self.pound_token.to_tokens(tokens);
        match self.style {
@ -215,7 +259,7 @@ impl<T: ToTokens> ToTokens for HdlAttr<T> {
            AttrStyle::Outer => {}
        };
        self.bracket_token.surround(tokens, |tokens| {
-            self.hdl.to_tokens(tokens);
+            self.kw.to_tokens(tokens);
            match self.paren_token {
                Some(paren_token) => {
                    paren_token.surround(tokens, |tokens| self.body.to_tokens(tokens))
@ -223,7 +267,7 @@ impl<T: ToTokens> ToTokens for HdlAttr<T> {
                None => {
                    let body = self.body.to_token_stream();
                    if !body.is_empty() {
-                        syn::token::Paren(self.hdl.span)
+                        syn::token::Paren(self.kw.span())
                            .surround(tokens, |tokens| tokens.extend([body]));
                    }
                }
@ -232,18 +276,24 @@ impl<T: ToTokens> ToTokens for HdlAttr<T> {
    }
 }

-fn is_hdl_attr(attr: &Attribute) -> bool {
-    attr.path().is_ident("hdl")
+fn is_hdl_attr<KW: CustomToken>(attr: &Attribute) -> bool {
+    attr.path().is_ident(KW::IDENT_STR)
 }

-impl<T: Parse> HdlAttr<T> {
-    fn parse_and_take_attr(attrs: &mut Vec<Attribute>) -> syn::Result<Option<Self>> {
+impl<T: Parse, KW: Parse> HdlAttr<T, KW> {
+    fn parse_and_take_attr(attrs: &mut Vec<Attribute>) -> syn::Result<Option<Self>>
+    where
+        KW: ToTokens,
+    {
        let mut retval = None;
        let mut errors = Errors::new();
        attrs.retain(|attr| {
-            if is_hdl_attr(attr) {
+            if let Ok(kw) = syn::parse2::<KW>(attr.path().to_token_stream()) {
                if retval.is_some() {
-                    errors.push(Error::new_spanned(attr, "more than one #[hdl] attribute"));
+                    errors.push(Error::new_spanned(
+                        attr,
+                        format_args!("more than one #[{}] attribute", kw.to_token_stream()),
+                    ));
                }
                errors.unwrap_or_default(Self::parse_attr(attr).map(|v| retval = Some(v)));
                false
@ -254,13 +304,19 @@ impl<T: Parse> HdlAttr<T> {
        errors.finish()?;
        Ok(retval)
    }
-    fn parse_and_leave_attr(attrs: &[Attribute]) -> syn::Result<Option<Self>> {
+    fn parse_and_leave_attr(attrs: &[Attribute]) -> syn::Result<Option<Self>>
+    where
+        KW: ToTokens,
+    {
        let mut retval = None;
        let mut errors = Errors::new();
        for attr in attrs {
-            if is_hdl_attr(attr) {
+            if let Ok(kw) = syn::parse2::<KW>(attr.path().to_token_stream()) {
                if retval.is_some() {
-                    errors.push(Error::new_spanned(attr, "more than one #[hdl] attribute"));
+                    errors.push(Error::new_spanned(
+                        attr,
+                        format_args!("more than one #[{}] attribute", kw.to_token_stream()),
+                    ));
                }
                errors.unwrap_or_default(Self::parse_attr(attr).map(|v| retval = Some(v)));
            }
@ -281,7 +337,7 @@ impl<T: Parse> HdlAttr<T> {
    ) -> syn::Result<Self> {
        let bracket_content;
        let bracket_token = bracketed!(bracket_content in input);
-        let hdl = bracket_content.parse()?;
+        let kw = bracket_content.parse()?;
        let paren_content;
        let body;
        let paren_token;
@ -302,7 +358,7 @@ impl<T: Parse> HdlAttr<T> {
            pound_token,
            style,
            bracket_token,
-            hdl,
+            kw,
            paren_token,
            body,
        })
@ -519,6 +575,26 @@ macro_rules! impl_extra_traits_for_options {
    ) => {
        impl Copy for $option_enum_name {}

+        impl PartialEq for $option_enum_name {
+            fn eq(&self, other: &Self) -> bool {
+                self.cmp(other).is_eq()
+            }
+        }
+
+        impl Eq for $option_enum_name {}
+
+        impl PartialOrd for $option_enum_name {
+            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+                Some(self.cmp(other))
+            }
+        }
+
+        impl Ord for $option_enum_name {
+            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+                self.variant().cmp(&other.variant())
+            }
+        }
+
        impl quote::IdentFragment for $option_enum_name {
            fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
                let _ = f;
@ -554,6 +630,66 @@ pub(crate) use impl_extra_traits_for_options;
 macro_rules! options {
    (
        #[options = $options_name:ident]
+        $($tt:tt)*
+    ) => {
+        crate::options! {
+            #[options = $options_name, punct = syn::Token![,], allow_duplicates = false]
+            $($tt)*
+        }
+    };
+    (
+        #[options = $options_name:ident, punct = $Punct:ty, allow_duplicates = true]
+        $(#[$($enum_meta:tt)*])*
+        $enum_vis:vis enum $option_enum_name:ident {
+            $($Variant:ident($key:ident $(, $value:ty)?),)*
+        }
+    ) => {
+        crate::options! {
+            #[options = $options_name, punct = $Punct, allow_duplicates = (true)]
+            $(#[$($enum_meta)*])*
+            $enum_vis enum $option_enum_name {
+                $($Variant($key $(, $value)?),)*
+            }
+        }
+
+        impl Extend<$option_enum_name> for $options_name {
+            fn extend<T: IntoIterator<Item = $option_enum_name>>(&mut self, iter: T) {
+                iter.into_iter().for_each(|v| match v {
+                    $($option_enum_name::$Variant(v) => {
+                        self.$key = Some(v);
+                    })*
+                });
+            }
+        }
+
+        impl FromIterator<$option_enum_name> for $options_name {
+            fn from_iter<T: IntoIterator<Item = $option_enum_name>>(iter: T) -> Self {
+                let mut retval = Self::default();
+                retval.extend(iter);
+                retval
+            }
+        }
+
+        impl Extend<$options_name> for $options_name {
+            fn extend<T: IntoIterator<Item = $options_name>>(&mut self, iter: T) {
+                iter.into_iter().for_each(|v| {
+                    $(if let Some(v) = v.$key {
+                        self.$key = Some(v);
+                    })*
+                });
+            }
+        }
+
+        impl FromIterator<$options_name> for $options_name {
+            fn from_iter<T: IntoIterator<Item = $options_name>>(iter: T) -> Self {
+                let mut retval = Self::default();
+                retval.extend(iter);
+                retval
+            }
+        }
+    };
+    (
+        #[options = $options_name:ident, punct = $Punct:ty, allow_duplicates = $allow_duplicates:expr]
        $(#[$($enum_meta:tt)*])*
        $enum_vis:vis enum $option_enum_name:ident {
            $($Variant:ident($key:ident $(, $value:ty)?),)*
@ -567,8 +703,11 @@ macro_rules! options {
        }

        #[derive(Clone, Debug, Default)]
+        #[allow(non_snake_case)]
        $enum_vis struct $options_name {
-            $($enum_vis $key: Option<(crate::kw::$key, $(syn::token::Paren, $value)?)>,)*
+            $(
+                $enum_vis $key: Option<(crate::kw::$key, $(syn::token::Paren, $value)?)>,
+            )*
        }

        crate::fold::impl_fold! {
@ -577,6 +716,43 @@ macro_rules! options {
            }
        }

+        const _: () = {
+            #[derive(Clone, Debug)]
+            $enum_vis struct Iter($enum_vis $options_name);
+
+            impl IntoIterator for $options_name {
+                type Item = $option_enum_name;
+                type IntoIter = Iter;
+
+                fn into_iter(self) -> Self::IntoIter {
+                    Iter(self)
+                }
+            }
+
+            impl Iterator for Iter {
+                type Item = $option_enum_name;
+
+                fn next(&mut self) -> Option<Self::Item> {
+                    $(
+                        if let Some(value) = self.0.$key.take() {
+                            return Some($option_enum_name::$Variant(value));
+                        }
+                    )*
+                    None
+                }
+
+                #[allow(unused_mut, unused_variables)]
+                fn fold<B, F: FnMut(B, Self::Item) -> B>(mut self, mut init: B, mut f: F) -> B {
+                    $(
+                        if let Some(value) = self.0.$key.take() {
+                            init = f(init, $option_enum_name::$Variant(value));
+                        }
+                    )*
+                    init
+                }
+            }
+        };
+
        impl syn::parse::Parse for $options_name {
            fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
                #![allow(unused_mut, unused_variables, unreachable_code)]
@ -585,7 +761,7 @@ macro_rules! options {
                    let old_input = input.fork();
                    match input.parse::<$option_enum_name>()? {
                        $($option_enum_name::$Variant(v) => {
-                            if retval.$key.replace(v).is_some() {
+                            if retval.$key.replace(v).is_some() && !$allow_duplicates {
                                return Err(old_input.error(concat!("duplicate ", stringify!($key), " option")));
                            }
                        })*
@ -593,7 +769,7 @@ macro_rules! options {
                    if input.is_empty() {
                        break;
                    }
-                    input.parse::<syn::Token![,]>()?;
+                    input.parse::<$Punct>()?;
                }
                Ok(retval)
            }
@ -602,7 +778,7 @@ macro_rules! options {
        impl quote::ToTokens for $options_name {
            #[allow(unused_mut, unused_variables, unused_assignments)]
            fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
-                let mut separator: Option<syn::Token![,]> = None;
+                let mut separator: Option<$Punct> = None;
                $(if let Some(v) = &self.$key {
                    separator.to_tokens(tokens);
                    separator = Some(Default::default());
@ -673,9 +849,24 @@ macro_rules! options {
                }
            }
        }
+
+        impl $option_enum_name {
+            #[allow(dead_code)]
+            fn variant(&self) -> usize {
+                #[repr(usize)]
+                enum Variant {
+                    $($Variant,)*
+                    __Last, // so it doesn't complain about zero-variant enums
+                }
+                match *self {
+                    $(Self::$Variant(..) => Variant::$Variant as usize,)*
+                }
+            }
+        }
    };
 }

+use crate::hdl_type_alias::hdl_type_alias_impl;
 pub(crate) use options;

 pub(crate) fn outline_generated(contents: TokenStream, prefix: &str) -> TokenStream {
@ -686,6 +877,15 @@ pub(crate) fn outline_generated(contents: TokenStream, prefix: &str) -> TokenStr
        .suffix(".tmp.rs")
        .tempfile_in(out_dir)
        .unwrap();
+    struct PrintOnPanic<'a>(&'a TokenStream);
+    impl Drop for PrintOnPanic<'_> {
+        fn drop(&mut self) {
+            if std::thread::panicking() {
+                println!("{}", self.0);
+            }
+        }
+    }
+    let _print_on_panic = PrintOnPanic(&contents);
    let contents = prettyplease::unparse(&parse_quote! { #contents });
    let hash = <sha2::Sha256 as sha2::Digest>::digest(&contents);
    let hash = base16ct::HexDisplay(&hash[..5]);
@ -706,25 +906,372 @@ pub(crate) fn outline_generated(contents: TokenStream, prefix: &str) -> TokenStr
    }
 }

-pub fn module(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
-    let options = syn::parse2::<module::ConfigOptions>(attr)?;
-    let options = HdlAttr::from(options);
-    let func = syn::parse2::<module::ModuleFn>(quote! { #options #item })?;
+fn hdl_module_impl(item: ItemFn) -> syn::Result<TokenStream> {
+    let func = module::ModuleFn::parse_from_fn(item)?;
+    let options = func.config_options();
    let mut contents = func.generate();
-    if options.body.outline_generated.is_some() {
+    if options.outline_generated.is_some() {
        contents = outline_generated(contents, "module-");
    }
    Ok(contents)
 }

-pub fn value_derive(item: TokenStream) -> syn::Result<TokenStream> {
-    let item = syn::parse2::<Item>(item)?;
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) enum CfgExpr {
+    Option {
+        ident: Ident,
+        value: Option<(Token![=], LitStr)>,
+    },
+    All {
+        all: kw::all,
+        paren: Paren,
+        exprs: Punctuated<CfgExpr, Token![,]>,
+    },
+    Any {
+        any: kw::any,
+        paren: Paren,
+        exprs: Punctuated<CfgExpr, Token![,]>,
+    },
+    Not {
+        not: kw::not,
+        paren: Paren,
+        expr: Box<CfgExpr>,
+        trailing_comma: Option<Token![,]>,
+    },
+}
+
+impl Parse for CfgExpr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        match input.cursor().ident() {
+            Some((_, cursor)) if cursor.eof() => {
+                return Ok(CfgExpr::Option {
+                    ident: input.call(Ident::parse_any)?,
+                    value: None,
+                });
+            }
+            _ => {}
+        }
+        if input.peek(Ident::peek_any) && input.peek2(Token![=]) {
+            return Ok(CfgExpr::Option {
+                ident: input.call(Ident::parse_any)?,
+                value: Some((input.parse()?, input.parse()?)),
+            });
+        }
+        let contents;
+        if input.peek(kw::all) {
+            Ok(CfgExpr::All {
+                all: input.parse()?,
+                paren: parenthesized!(contents in input),
+                exprs: contents.call(Punctuated::parse_terminated)?,
+            })
+        } else if input.peek(kw::any) {
+            Ok(CfgExpr::Any {
+                any: input.parse()?,
+                paren: parenthesized!(contents in input),
+                exprs: contents.call(Punctuated::parse_terminated)?,
+            })
+        } else if input.peek(kw::not) {
+            Ok(CfgExpr::Not {
+                not: input.parse()?,
+                paren: parenthesized!(contents in input),
+                expr: contents.parse()?,
+                trailing_comma: contents.parse()?,
+            })
+        } else {
+            Err(input.error("expected cfg-pattern"))
+        }
+    }
+}
+
+impl ToTokens for CfgExpr {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            CfgExpr::Option { ident, value } => {
+                ident.to_tokens(tokens);
+                if let Some((eq, value)) = value {
+                    eq.to_tokens(tokens);
+                    value.to_tokens(tokens);
+                }
+            }
+            CfgExpr::All { all, paren, exprs } => {
+                all.to_tokens(tokens);
+                paren.surround(tokens, |tokens| exprs.to_tokens(tokens));
+            }
+            CfgExpr::Any { any, paren, exprs } => {
+                any.to_tokens(tokens);
+                paren.surround(tokens, |tokens| exprs.to_tokens(tokens));
+            }
+            CfgExpr::Not {
+                not,
+                paren,
+                expr,
+                trailing_comma,
+            } => {
+                not.to_tokens(tokens);
+                paren.surround(tokens, |tokens| {
+                    expr.to_tokens(tokens);
+                    trailing_comma.to_tokens(tokens);
+                });
+            }
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct Cfg {
+    cfg: kw::cfg,
+    paren: Paren,
+    expr: CfgExpr,
+    trailing_comma: Option<Token![,]>,
+}
+
+impl Cfg {
+    fn parse_meta(meta: &Meta) -> syn::Result<Self> {
+        syn::parse2(meta.to_token_stream())
+    }
+}
+
+impl ToTokens for Cfg {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            cfg,
+            paren,
+            expr,
+            trailing_comma,
+        } = self;
+        cfg.to_tokens(tokens);
+        paren.surround(tokens, |tokens| {
+            expr.to_tokens(tokens);
+            trailing_comma.to_tokens(tokens);
+        });
+    }
+}
+
+impl Parse for Cfg {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        Ok(Self {
+            cfg: input.parse()?,
+            paren: parenthesized!(contents in input),
+            expr: contents.parse()?,
+            trailing_comma: contents.parse()?,
+        })
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct CfgAttr {
+    cfg_attr: kw::cfg_attr,
+    paren: Paren,
+    expr: CfgExpr,
+    comma: Token![,],
+    attrs: Punctuated<Meta, Token![,]>,
+}
+
+impl CfgAttr {
+    pub(crate) fn to_cfg(&self) -> Cfg {
+        Cfg {
+            cfg: kw::cfg(self.cfg_attr.span),
+            paren: self.paren,
+            expr: self.expr.clone(),
+            trailing_comma: None,
+        }
+    }
+    fn parse_meta(meta: &Meta) -> syn::Result<Self> {
+        syn::parse2(meta.to_token_stream())
+    }
+}
+
+impl Parse for CfgAttr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        Ok(Self {
+            cfg_attr: input.parse()?,
+            paren: parenthesized!(contents in input),
+            expr: contents.parse()?,
+            comma: contents.parse()?,
+            attrs: contents.call(Punctuated::parse_terminated)?,
+        })
+    }
+}
+
+pub(crate) struct CfgAndValue {
+    cfg: Cfg,
+    eq_token: Token![=],
+    value: LitBool,
+}
+
+impl Parse for CfgAndValue {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        Ok(Self {
+            cfg: input.parse()?,
+            eq_token: input.parse()?,
+            value: input.parse()?,
+        })
+    }
+}
+
+pub(crate) struct Cfgs<T> {
+    pub(crate) bracket: Bracket,
+    pub(crate) cfgs_map: HashMap<Cfg, T>,
+    pub(crate) cfgs_list: Vec<Cfg>,
+}
+
+impl<T> Default for Cfgs<T> {
+    fn default() -> Self {
+        Self {
+            bracket: Default::default(),
+            cfgs_map: Default::default(),
+            cfgs_list: Default::default(),
+        }
+    }
+}
+
+impl<T> Cfgs<T> {
+    fn insert_cfg(&mut self, cfg: Cfg, value: T) {
+        match self.cfgs_map.entry(cfg) {
+            Entry::Occupied(_) => {}
+            Entry::Vacant(entry) => {
+                self.cfgs_list.push(entry.key().clone());
+                entry.insert(value);
+            }
+        }
+    }
+}
+
+impl Parse for Cfgs<bool> {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        let bracket = bracketed!(contents in input);
+        let mut cfgs_map = HashMap::new();
+        let mut cfgs_list = Vec::new();
+        for CfgAndValue {
+            cfg,
+            eq_token,
+            value,
+        } in contents.call(Punctuated::<CfgAndValue, Token![,]>::parse_terminated)?
+        {
+            let _ = eq_token;
+            match cfgs_map.entry(cfg) {
+                Entry::Occupied(_) => {}
+                Entry::Vacant(entry) => {
+                    cfgs_list.push(entry.key().clone());
+                    entry.insert(value.value);
+                }
+            }
+        }
+        Ok(Self {
+            bracket,
+            cfgs_map,
+            cfgs_list,
+        })
+    }
+}
+
+impl Parse for Cfgs<()> {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let contents;
+        let bracket = bracketed!(contents in input);
+        let mut cfgs_map = HashMap::new();
+        let mut cfgs_list = Vec::new();
+        for cfg in contents.call(Punctuated::<Cfg, Token![,]>::parse_terminated)? {
+            match cfgs_map.entry(cfg) {
+                Entry::Occupied(_) => {}
+                Entry::Vacant(entry) => {
+                    cfgs_list.push(entry.key().clone());
+                    entry.insert(());
+                }
+            }
+        }
+        Ok(Self {
+            bracket,
+            cfgs_map,
+            cfgs_list,
+        })
+    }
+}
+
+impl ToTokens for Cfgs<()> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            bracket,
+            cfgs_map: _,
+            cfgs_list,
+        } = self;
+        bracket.surround(tokens, |tokens| {
+            for cfg in cfgs_list {
+                cfg.to_tokens(tokens);
+                <Token![,]>::default().to_tokens(tokens);
+            }
+        });
+    }
+}
+
+fn hdl_main(
+    kw: impl CustomToken,
+    attr: TokenStream,
+    item: TokenStream,
+) -> syn::Result<TokenStream> {
+    fn parse_evaluated_cfgs_attr<R>(
+        input: ParseStream,
+        parse_inner: impl FnOnce(ParseStream) -> syn::Result<R>,
+    ) -> syn::Result<R> {
+        let _: Token![#] = input.parse()?;
+        let bracket_content;
+        bracketed!(bracket_content in input);
+        let _: kw::__evaluated_cfgs = bracket_content.parse()?;
+        let paren_content;
+        parenthesized!(paren_content in bracket_content);
+        parse_inner(&paren_content)
+    }
+    let (evaluated_cfgs, item): (_, TokenStream) = Parser::parse2(
+        |input: ParseStream| {
+            let peek = input.fork();
+            if parse_evaluated_cfgs_attr(&peek, |_| Ok(())).is_ok() {
+                let evaluated_cfgs = parse_evaluated_cfgs_attr(input, Cfgs::<bool>::parse)?;
+                Ok((Some(evaluated_cfgs), input.parse()?))
+            } else {
+                Ok((None, input.parse()?))
+            }
+        },
+        item,
+    )?;
+    let cfgs = if let Some(cfgs) = evaluated_cfgs {
+        cfgs
+    } else {
+        let cfgs = process_cfg::collect_cfgs(syn::parse2(item.clone())?)?;
+        if cfgs.cfgs_list.is_empty() {
+            Cfgs::default()
+        } else {
+            return Ok(quote! {
+                ::fayalite::__cfg_expansion_helper! {
+                    []
+                    #cfgs
+                    {#[::fayalite::#kw(#attr)]} { #item }
+                }
+            });
+        }
+    };
+    let item = syn::parse2(quote! { #[#kw(#attr)] #item })?;
+    let Some(item) = process_cfg::process_cfgs(item, cfgs)? else {
+        return Ok(TokenStream::new());
+    };
    match item {
-        Item::Enum(item) => value_derive_enum::value_derive_enum(item),
-        Item::Struct(item) => value_derive_struct::value_derive_struct(item),
+        Item::Enum(item) => hdl_enum::hdl_enum(item),
+        Item::Struct(item) => hdl_bundle::hdl_bundle(item),
+        Item::Fn(item) => hdl_module_impl(item),
+        Item::Type(item) => hdl_type_alias_impl(item),
        _ => Err(syn::Error::new(
            Span::call_site(),
-            "derive(Value) can only be used on structs or enums",
+            "top-level #[hdl] can only be used on structs, enums, type aliases, or functions",
        )),
    }
 }
+
+pub fn hdl_module(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
+    hdl_main(kw::hdl_module::default(), attr, item)
+}
+
+pub fn hdl_attr(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
+    hdl_main(kw::hdl::default(), attr, item)
+}
--- a/crates/fayalite-proc-macros-impl/src/module.rs
+++ b/crates/fayalite-proc-macros-impl/src/module.rs
@ -1,7 +1,8 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    is_hdl_attr,
+    hdl_type_common::{ParsedGenerics, SplitForImpl},
+    kw,
    module::transform_body::{HdlLet, HdlLetKindIO},
    options, Errors, HdlAttr, PairsIterExt,
 };
@ -9,7 +10,6 @@ use proc_macro2::TokenStream;
 use quote::{format_ident, quote, quote_spanned, ToTokens};
 use std::collections::HashSet;
 use syn::{
-    parse::{Parse, ParseStream},
    parse_quote,
    visit::{visit_pat, Visit},
    Attribute, Block, ConstParam, Error, FnArg, GenericParam, Generics, Ident, ItemFn, ItemStruct,
@ -57,26 +57,39 @@ impl Visit<'_> for CheckNameConflictsWithModuleBuilderVisitor<'_> {
    }
 }

-fn retain_struct_attrs<F: FnMut(&Attribute) -> bool>(item: &mut ItemStruct, mut f: F) {
-    item.attrs.retain(&mut f);
-    for field in item.fields.iter_mut() {
-        field.attrs.retain(&mut f);
-    }
-}
-
 pub(crate) type ModuleIO = HdlLet<HdlLetKindIO>;

-pub(crate) struct ModuleFn {
+struct ModuleFnModule {
    attrs: Vec<Attribute>,
-    config_options: HdlAttr<ConfigOptions>,
+    config_options: HdlAttr<ConfigOptions, kw::hdl_module>,
    module_kind: ModuleKind,
    vis: Visibility,
    sig: Signature,
    block: Box<Block>,
-    io: Vec<ModuleIO>,
-    struct_generics: Generics,
+    struct_generics: ParsedGenerics,
+    the_struct: TokenStream,
 }

+enum ModuleFnImpl {
+    Module(ModuleFnModule),
+    Fn {
+        attrs: Vec<Attribute>,
+        config_options: HdlAttr<ConfigOptions, kw::hdl>,
+        vis: Visibility,
+        sig: Signature,
+        block: Box<Block>,
+    },
+}
+
+options! {
+    pub(crate) enum HdlOrHdlModule {
+        Hdl(hdl),
+        HdlModule(hdl_module),
+    }
+}
+
+pub(crate) struct ModuleFn(ModuleFnImpl);
+
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub(crate) enum ModuleKind {
    Extern,
@ -96,14 +109,25 @@ impl Visit<'_> for ContainsSkippedIdent<'_> {
    }
 }

-impl Parse for ModuleFn {
-    fn parse(input: ParseStream) -> syn::Result<Self> {
+impl ModuleFn {
+    pub(crate) fn config_options(&self) -> ConfigOptions {
+        let (ModuleFnImpl::Module(ModuleFnModule {
+            config_options: HdlAttr { body, .. },
+            ..
+        })
+        | ModuleFnImpl::Fn {
+            config_options: HdlAttr { body, .. },
+            ..
+        }) = &self.0;
+        body.clone()
+    }
+    pub(crate) fn parse_from_fn(item: ItemFn) -> syn::Result<Self> {
        let ItemFn {
            mut attrs,
            vis,
            mut sig,
            block,
-        } = input.parse()?;
+        } = item;
        let Signature {
            ref constness,
            ref asyncness,
@ -118,43 +142,60 @@ impl Parse for ModuleFn {
            ref output,
        } = sig;
        let mut errors = Errors::new();
-        let config_options = errors
-            .unwrap_or_default(HdlAttr::parse_and_take_attr(&mut attrs))
-            .unwrap_or_default();
+        let Some(mut config_options) =
+            errors.unwrap_or_default(
+                HdlAttr::<ConfigOptions, HdlOrHdlModule>::parse_and_take_attr(&mut attrs),
+            )
+        else {
+            errors.error(sig.ident, "missing #[hdl] or #[hdl_module] attribute");
+            errors.finish()?;
+            unreachable!();
+        };
        let ConfigOptions {
            outline_generated: _,
            extern_,
        } = config_options.body;
-        let module_kind = match extern_ {
-            Some(_) => ModuleKind::Extern,
-            None => ModuleKind::Normal,
+        let module_kind = match (config_options.kw, extern_) {
+            (HdlOrHdlModule::Hdl(_), None) => None,
+            (HdlOrHdlModule::Hdl(_), Some(extern2)) => {
+                config_options.body.extern_ = None;
+                errors.error(
+                    extern2.0,
+                    "extern can only be used as #[hdl_module(extern)]",
+                );
+                None
+            }
+            (HdlOrHdlModule::HdlModule(_), None) => Some(ModuleKind::Normal),
+            (HdlOrHdlModule::HdlModule(_), Some(_)) => Some(ModuleKind::Extern),
        };
-        for fn_arg in inputs {
-            match fn_arg {
-                FnArg::Receiver(_) => {
-                    errors.push(syn::Error::new_spanned(fn_arg, "self not allowed here"));
-                }
-                FnArg::Typed(fn_arg) => {
-                    visit_pat(
-                        &mut CheckNameConflictsWithModuleBuilderVisitor {
-                            errors: &mut errors,
-                        },
-                        &fn_arg.pat,
-                    );
+        if let HdlOrHdlModule::HdlModule(_) = config_options.kw {
+            for fn_arg in inputs {
+                match fn_arg {
+                    FnArg::Receiver(_) => {
+                        errors.push(syn::Error::new_spanned(fn_arg, "self not allowed here"));
+                    }
+                    FnArg::Typed(fn_arg) => {
+                        visit_pat(
+                            &mut CheckNameConflictsWithModuleBuilderVisitor {
+                                errors: &mut errors,
+                            },
+                            &fn_arg.pat,
+                        );
+                    }
                }
            }
-        }
-        if let Some(constness) = constness {
-            errors.push(syn::Error::new_spanned(constness, "const not allowed here"));
-        }
-        if let Some(asyncness) = asyncness {
-            errors.push(syn::Error::new_spanned(asyncness, "async not allowed here"));
-        }
-        if let Some(unsafety) = unsafety {
-            errors.push(syn::Error::new_spanned(unsafety, "unsafe not allowed here"));
-        }
-        if let Some(abi) = abi {
-            errors.push(syn::Error::new_spanned(abi, "extern not allowed here"));
+            if let Some(constness) = constness {
+                errors.push(syn::Error::new_spanned(constness, "const not allowed here"));
+            }
+            if let Some(asyncness) = asyncness {
+                errors.push(syn::Error::new_spanned(asyncness, "async not allowed here"));
+            }
+            if let Some(unsafety) = unsafety {
+                errors.push(syn::Error::new_spanned(unsafety, "unsafe not allowed here"));
+            }
+            if let Some(abi) = abi {
+                errors.push(syn::Error::new_spanned(abi, "extern not allowed here"));
+            }
        }
        let mut skipped_idents = HashSet::new();
        let struct_generic_params = generics
@ -162,14 +203,17 @@ impl Parse for ModuleFn {
            .pairs_mut()
            .filter_map_pair_value_mut(|v| match v {
                GenericParam::Lifetime(LifetimeParam { attrs, .. }) => {
-                    errors
-                        .unwrap_or_default(HdlAttr::<crate::kw::skip>::parse_and_take_attr(attrs));
+                    errors.unwrap_or_default(
+                        HdlAttr::<crate::kw::skip, kw::hdl>::parse_and_take_attr(attrs),
+                    );
                    None
                }
                GenericParam::Type(TypeParam { attrs, ident, .. })
                | GenericParam::Const(ConstParam { attrs, ident, .. }) => {
                    if errors
-                        .unwrap_or_default(HdlAttr::<crate::kw::skip>::parse_and_take_attr(attrs))
+                        .unwrap_or_default(
+                            HdlAttr::<crate::kw::skip, kw::hdl>::parse_and_take_attr(attrs),
+                        )
                        .is_some()
                    {
                        skipped_idents.insert(ident.clone());
@ -183,6 +227,7 @@ impl Parse for ModuleFn {
        let struct_where_clause = generics
            .where_clause
            .as_mut()
+            .filter(|_| matches!(config_options.kw, HdlOrHdlModule::HdlModule(_)))
            .map(|where_clause| WhereClause {
                where_token: where_clause.where_token,
                predicates: where_clause
@ -205,49 +250,158 @@ impl Parse for ModuleFn {
                    })
                    .collect(),
            });
-        let struct_generics = Generics {
-            lt_token: generics.lt_token,
-            params: struct_generic_params,
-            gt_token: generics.gt_token,
-            where_clause: struct_where_clause,
+        let struct_generics = if let HdlOrHdlModule::HdlModule(_) = config_options.kw {
+            let mut struct_generics = Generics {
+                lt_token: generics.lt_token,
+                params: struct_generic_params,
+                gt_token: generics.gt_token,
+                where_clause: struct_where_clause,
+            };
+            if let Some(variadic) = variadic {
+                errors.push(syn::Error::new_spanned(variadic, "... not allowed here"));
+            }
+            if !matches!(output, ReturnType::Default) {
+                errors.push(syn::Error::new_spanned(
+                    output,
+                    "return type not allowed here",
+                ));
+            }
+            errors.ok(ParsedGenerics::parse(&mut struct_generics))
+        } else {
+            Some(ParsedGenerics::default())
        };
-        if let Some(variadic) = variadic {
-            errors.push(syn::Error::new_spanned(variadic, "... not allowed here"));
-        }
-        if !matches!(output, ReturnType::Default) {
-            errors.push(syn::Error::new_spanned(
-                output,
-                "return type not allowed here",
-            ));
-        }
-        let body_results = errors.ok(transform_body::transform_body(module_kind, block));
+        let body_results = struct_generics.as_ref().and_then(|struct_generics| {
+            errors.ok(transform_body::transform_body(
+                module_kind,
+                block,
+                struct_generics,
+            ))
+        });
        errors.finish()?;
+        let struct_generics = struct_generics.unwrap();
        let (block, io) = body_results.unwrap();
-        Ok(Self {
+        let config_options = match config_options {
+            HdlAttr {
+                pound_token,
+                style,
+                bracket_token,
+                kw: HdlOrHdlModule::Hdl((kw,)),
+                paren_token,
+                body,
+            } => {
+                debug_assert!(io.is_empty());
+                return Ok(Self(ModuleFnImpl::Fn {
+                    attrs,
+                    config_options: HdlAttr {
+                        pound_token,
+                        style,
+                        bracket_token,
+                        kw,
+                        paren_token,
+                        body,
+                    },
+                    vis,
+                    sig,
+                    block,
+                }));
+            }
+            HdlAttr {
+                pound_token,
+                style,
+                bracket_token,
+                kw: HdlOrHdlModule::HdlModule((kw,)),
+                paren_token,
+                body,
+            } => HdlAttr {
+                pound_token,
+                style,
+                bracket_token,
+                kw,
+                paren_token,
+                body,
+            },
+        };
+        let (_struct_impl_generics, _struct_type_generics, struct_where_clause) =
+            struct_generics.split_for_impl();
+        let struct_where_clause: Option<WhereClause> = parse_quote! { #struct_where_clause };
+        if let Some(struct_where_clause) = &struct_where_clause {
+            sig.generics
+                .where_clause
+                .get_or_insert_with(|| WhereClause {
+                    where_token: struct_where_clause.where_token,
+                    predicates: Default::default(),
+                })
+                .predicates
+                .extend(struct_where_clause.predicates.clone());
+        }
+        let fn_name = &sig.ident;
+        let io_flips = io
+            .iter()
+            .map(|io| match io.kind.kind {
+                ModuleIOKind::Input((input,)) => quote_spanned! {input.span=>
+                    #[hdl(flip)]
+                },
+                ModuleIOKind::Output(_) => quote! {},
+            })
+            .collect::<Vec<_>>();
+        let io_types = io.iter().map(|io| &io.kind.ty).collect::<Vec<_>>();
+        let io_names = io.iter().map(|io| &io.name).collect::<Vec<_>>();
+        let the_struct: ItemStruct = parse_quote! {
+            #[allow(non_camel_case_types)]
+            #[hdl(no_runtime_generics, no_static)]
+            #vis struct #fn_name #struct_generics #struct_where_clause {
+                #(
+                #io_flips
+                #vis #io_names: #io_types,)*
+            }
+        };
+        let the_struct = crate::hdl_bundle::hdl_bundle(the_struct)?;
+        Ok(Self(ModuleFnImpl::Module(ModuleFnModule {
            attrs,
            config_options,
-            module_kind,
+            module_kind: module_kind.unwrap(),
            vis,
            sig,
            block,
-            io,
            struct_generics,
-        })
+            the_struct,
+        })))
    }
 }

 impl ModuleFn {
    pub(crate) fn generate(self) -> TokenStream {
-        let Self {
+        let ModuleFnModule {
            attrs,
            config_options,
            module_kind,
            vis,
            sig,
-            block,
-            io,
+            mut block,
            struct_generics,
-        } = self;
+            the_struct,
+        } = match self.0 {
+            ModuleFnImpl::Module(v) => v,
+            ModuleFnImpl::Fn {
+                attrs,
+                config_options,
+                vis,
+                sig,
+                block,
+            } => {
+                let ConfigOptions {
+                    outline_generated: _,
+                    extern_: _,
+                } = config_options.body;
+                return ItemFn {
+                    attrs,
+                    vis,
+                    sig,
+                    block,
+                }
+                .into_token_stream();
+            }
+        };
        let ConfigOptions {
            outline_generated: _,
            extern_: _,
@ -273,18 +427,23 @@ impl ModuleFn {
                });
                name
            }));
-        let module_kind_ty = match module_kind {
-            ModuleKind::Extern => quote! { ::fayalite::module::ExternModule },
-            ModuleKind::Normal => quote! { ::fayalite::module::NormalModule },
+        let module_kind_value = match module_kind {
+            ModuleKind::Extern => quote! { ::fayalite::module::ModuleKind::Extern },
+            ModuleKind::Normal => quote! { ::fayalite::module::ModuleKind::Normal },
        };
        let fn_name = &outer_sig.ident;
-        let (_struct_impl_generics, struct_type_generics, struct_where_clause) =
+        let (_struct_impl_generics, struct_type_generics, _struct_where_clause) =
            struct_generics.split_for_impl();
        let struct_ty = quote! {#fn_name #struct_type_generics};
        body_sig.ident = parse_quote! {__body};
-        body_sig.inputs.insert(
+        body_sig
+            .inputs
+            .insert(0, parse_quote! { m: &::fayalite::module::ModuleBuilder });
+        block.stmts.insert(
            0,
-            parse_quote! {m: &mut ::fayalite::module::ModuleBuilder<#struct_ty, #module_kind_ty>},
+            parse_quote! {
+                let _ = m;
+            },
        );
        let body_fn = ItemFn {
            attrs: vec![],
@ -294,50 +453,26 @@ impl ModuleFn {
        };
        outer_sig.output =
            parse_quote! {-> ::fayalite::intern::Interned<::fayalite::module::Module<#struct_ty>>};
-        let io_flips = io
-            .iter()
-            .map(|io| match io.kind.kind {
-                ModuleIOKind::Input((input,)) => quote_spanned! {input.span=>
-                    #[hdl(flip)]
-                },
-                ModuleIOKind::Output(_) => quote! {},
-            })
-            .collect::<Vec<_>>();
-        let io_types = io.iter().map(|io| &io.kind.ty).collect::<Vec<_>>();
-        let io_names = io.iter().map(|io| &io.name).collect::<Vec<_>>();
        let fn_name_str = fn_name.to_string();
        let (_, body_type_generics, _) = body_fn.sig.generics.split_for_impl();
        let body_turbofish_type_generics = body_type_generics.as_turbofish();
-        let block = parse_quote! {{
-            #body_fn
-            ::fayalite::module::ModuleBuilder::run(#fn_name_str, |m| __body #body_turbofish_type_generics(m, #(#param_names,)*))
-        }};
-        let static_type = io.iter().all(|io| io.kind.ty_expr.is_none());
-        let struct_options = if static_type {
-            quote! { #[hdl(static)] }
+        let body_lambda = if param_names.is_empty() {
+            quote! {
+                __body #body_turbofish_type_generics
+            }
        } else {
-            quote! {}
-        };
-        let the_struct: ItemStruct = parse_quote! {
-            #[derive(::fayalite::__std::clone::Clone,
-                ::fayalite::__std::hash::Hash,
-                ::fayalite::__std::cmp::PartialEq,
-                ::fayalite::__std::cmp::Eq,
-                ::fayalite::__std::fmt::Debug)]
-            #[allow(non_camel_case_types)]
-            #struct_options
-            #vis struct #fn_name #struct_generics #struct_where_clause {
-                #(
-                #io_flips
-                #vis #io_names: #io_types,)*
+            quote! {
+                |m| __body #body_turbofish_type_generics(m, #(#param_names,)*)
            }
        };
-        let mut struct_without_hdl_attrs = the_struct.clone();
-        let mut struct_without_derives = the_struct;
-        retain_struct_attrs(&mut struct_without_hdl_attrs, |attr| !is_hdl_attr(attr));
-        retain_struct_attrs(&mut struct_without_derives, |attr| {
-            !attr.path().is_ident("derive")
-        });
+        let block = parse_quote! {{
+            #body_fn
+            ::fayalite::module::ModuleBuilder::run(
+                #fn_name_str,
+                #module_kind_value,
+                #body_lambda,
+            )
+        }};
        let outer_fn = ItemFn {
            attrs,
            vis,
@ -345,10 +480,7 @@ impl ModuleFn {
            block,
        };
        let mut retval = outer_fn.into_token_stream();
-        struct_without_hdl_attrs.to_tokens(&mut retval);
-        retval.extend(
-            crate::value_derive_struct::value_derive_struct(struct_without_derives).unwrap(),
-        );
+        retval.extend(the_struct);
        retval
    }
 }
--- a/crates/fayalite-proc-macros-impl/src/module/transform_body.rs
+++ b/crates/fayalite-proc-macros-impl/src/module/transform_body.rs
--- a/crates/fayalite-proc-macros-impl/src/module/transform_body/expand_aggregate_literals.rs
+++ b/crates/fayalite-proc-macros-impl/src/module/transform_body/expand_aggregate_literals.rs
@ -1,540 +1,274 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
-use crate::{module::transform_body::Visitor, options, Errors, HdlAttr, PairsIterExt};
-use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote_spanned, ToTokens, TokenStreamExt};
+
+use crate::{
+    kw,
+    module::transform_body::{
+        expand_match::{parse_enum_path, EnumPath},
+        ExprOptions, Visitor,
+    },
+    HdlAttr,
+};
+use quote::{format_ident, quote_spanned};
+use std::mem;
 use syn::{
-    parse::Nothing,
-    parse_quote, parse_quote_spanned,
-    punctuated::{Pair, Punctuated},
-    spanned::Spanned,
-    token::{Brace, Paren},
-    Attribute, Expr, ExprArray, ExprCall, ExprGroup, ExprPath, ExprRepeat, ExprStruct, ExprTuple,
-    FieldValue, Ident, Index, Member, Path, PathArguments, PathSegment, Token, TypePath,
+    parse_quote_spanned, punctuated::Punctuated, spanned::Spanned, token::Paren, Expr, ExprArray,
+    ExprCall, ExprGroup, ExprMethodCall, ExprParen, ExprPath, ExprRepeat, ExprStruct, ExprTuple,
+    FieldValue, Token, TypePath,
 };

-options! {
-    #[options = AggregateLiteralOptions]
-    #[no_ident_fragment]
-    pub(crate) enum AggregateLiteralOption {
-        Struct(struct_),
-        Enum(enum_),
-    }
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct StructOrEnumPath {
-    pub(crate) ty: TypePath,
-    pub(crate) variant: Option<(TypePath, Ident)>,
-}
-
-#[derive(Debug, Copy, Clone)]
-pub(crate) struct SingleSegmentVariant {
-    pub(crate) name: &'static str,
-    pub(crate) make_type_path: fn(Span, &PathArguments) -> Path,
-}
-
-impl StructOrEnumPath {
-    pub(crate) const SINGLE_SEGMENT_VARIANTS: &'static [SingleSegmentVariant] = {
-        fn make_option_type_path(span: Span, arguments: &PathArguments) -> Path {
-            let arguments = if arguments.is_none() {
-                quote_spanned! {span=>
-                    <_>
-                }
-            } else {
-                arguments.to_token_stream()
-            };
-            parse_quote_spanned! {span=>
-                ::fayalite::__std::option::Option #arguments
-            }
-        }
-        fn make_result_type_path(span: Span, arguments: &PathArguments) -> Path {
-            let arguments = if arguments.is_none() {
-                quote_spanned! {span=>
-                    <_, _>
-                }
-            } else {
-                arguments.to_token_stream()
-            };
-            parse_quote_spanned! {span=>
-                ::fayalite::__std::result::Result #arguments
-            }
-        }
-        &[
-            SingleSegmentVariant {
-                name: "Some",
-                make_type_path: make_option_type_path,
-            },
-            SingleSegmentVariant {
-                name: "None",
-                make_type_path: make_option_type_path,
-            },
-            SingleSegmentVariant {
-                name: "Ok",
-                make_type_path: make_result_type_path,
-            },
-            SingleSegmentVariant {
-                name: "Err",
-                make_type_path: make_result_type_path,
-            },
-        ]
-    };
-    pub(crate) fn new(
-        errors: &mut Errors,
-        path: TypePath,
-        options: &AggregateLiteralOptions,
-    ) -> Result<Self, ()> {
-        let Path {
-            leading_colon,
-            segments,
-        } = &path.path;
-        let qself_position = path.qself.as_ref().map(|qself| qself.position).unwrap_or(0);
-        let variant_name = if qself_position < segments.len() {
-            Some(segments.last().unwrap().ident.clone())
-        } else {
-            None
-        };
-        let enum_type = 'guess_enum_type: {
-            if options.enum_.is_some() {
-                if let Some((struct_,)) = options.struct_ {
-                    errors.error(
-                        struct_,
-                        "can't specify both #[hdl(enum)] and #[hdl(struct)]",
-                    );
-                }
-                break 'guess_enum_type Some(None);
-            }
-            if options.struct_.is_some() {
-                break 'guess_enum_type None;
-            }
-            if path.qself.is_none() && leading_colon.is_none() && segments.len() == 1 {
-                let PathSegment { ident, arguments } = &segments[0];
-                for &SingleSegmentVariant {
-                    name,
-                    make_type_path,
-                } in Self::SINGLE_SEGMENT_VARIANTS
-                {
-                    if ident == name {
-                        break 'guess_enum_type Some(Some(TypePath {
-                            qself: None,
-                            path: make_type_path(ident.span(), arguments),
-                        }));
-                    }
-                }
-            }
-            if segments.len() == qself_position + 2
-                && segments[qself_position + 1].arguments.is_none()
-                && (path.qself.is_some()
-                    || segments[qself_position].ident.to_string().as_bytes()[0]
-                        .is_ascii_uppercase())
-            {
-                let mut ty = path.clone();
-                ty.path.segments.pop();
-                ty.path.segments.pop_punct();
-                break 'guess_enum_type Some(Some(ty));
-            }
-            None
-        };
-        if let Some(enum_type) = enum_type {
-            let ty = if let Some(enum_type) = enum_type {
-                enum_type
-            } else {
-                if qself_position >= segments.len() {
-                    errors.error(path, "#[hdl]: can't figure out enum's type");
-                    return Err(());
-                }
-                let mut ty = path.clone();
-                ty.path.segments.pop();
-                ty.path.segments.pop_punct();
-                ty
-            };
-            let Some(variant_name) = variant_name else {
-                errors.error(path, "#[hdl]: can't figure out enum's variant name");
-                return Err(());
-            };
-            Ok(Self {
-                ty,
-                variant: Some((path, variant_name)),
-            })
-        } else {
-            Ok(Self {
-                ty: path,
-                variant: None,
-            })
-        }
-    }
-}
-
-#[derive(Copy, Clone, Debug)]
-pub(crate) enum BraceOrParen {
-    Brace(Brace),
-    Paren(Paren),
-}
-
-impl BraceOrParen {
-    pub(crate) fn surround(self, tokens: &mut TokenStream, f: impl FnOnce(&mut TokenStream)) {
-        match self {
-            BraceOrParen::Brace(v) => v.surround(tokens, f),
-            BraceOrParen::Paren(v) => v.surround(tokens, f),
-        }
-    }
-}
-
-#[derive(Debug, Clone)]
-pub(crate) struct StructOrEnumLiteralField {
-    pub(crate) attrs: Vec<Attribute>,
-    pub(crate) member: Member,
-    pub(crate) colon_token: Option<Token![:]>,
-    pub(crate) expr: Expr,
-}
-
-#[derive(Debug, Clone)]
-pub(crate) struct StructOrEnumLiteral {
-    pub(crate) attrs: Vec<Attribute>,
-    pub(crate) path: TypePath,
-    pub(crate) brace_or_paren: BraceOrParen,
-    pub(crate) fields: Punctuated<StructOrEnumLiteralField, Token![,]>,
-    pub(crate) dot2_token: Option<Token![..]>,
-    pub(crate) rest: Option<Box<Expr>>,
-}
-
-impl StructOrEnumLiteral {
-    pub(crate) fn map_field_exprs(self, mut f: impl FnMut(Expr) -> Expr) -> Self {
-        self.map_fields(|mut field| {
-            field.expr = f(field.expr);
-            field
-        })
-    }
-    pub(crate) fn map_fields(
-        self,
-        f: impl FnMut(StructOrEnumLiteralField) -> StructOrEnumLiteralField,
-    ) -> Self {
-        let Self {
-            attrs,
-            path,
-            brace_or_paren,
-            fields,
-            dot2_token,
-            rest,
-        } = self;
-        let fields = fields.into_pairs().map_pair_value(f).collect();
-        Self {
-            attrs,
-            path,
-            brace_or_paren,
-            fields,
-            dot2_token,
-            rest,
-        }
-    }
-}
-
-impl From<ExprStruct> for StructOrEnumLiteral {
-    fn from(value: ExprStruct) -> Self {
-        let ExprStruct {
-            attrs,
-            qself,
-            path,
-            brace_token,
-            fields,
-            dot2_token,
-            rest,
-        } = value;
-        Self {
-            attrs,
-            path: TypePath { qself, path },
-            brace_or_paren: BraceOrParen::Brace(brace_token),
-            fields: fields
-                .into_pairs()
-                .map_pair_value(
-                    |FieldValue {
-                         attrs,
-                         member,
-                         colon_token,
-                         expr,
-                     }| StructOrEnumLiteralField {
-                        attrs,
-                        member,
-                        colon_token,
-                        expr,
-                    },
-                )
-                .collect(),
-            dot2_token,
-            rest,
-        }
-    }
-}
-
-fn expr_to_member(expr: &Expr) -> Option<Member> {
-    syn::parse2(expr.to_token_stream()).ok()
-}
-
-impl ToTokens for StructOrEnumLiteral {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        let Self {
-            attrs,
-            path,
-            brace_or_paren,
-            fields,
-            dot2_token,
-            rest,
-        } = self;
-        tokens.append_all(attrs);
-        path.to_tokens(tokens);
-        brace_or_paren.surround(tokens, |tokens| {
-            match brace_or_paren {
-                BraceOrParen::Brace(_) => {
-                    for (
-                        StructOrEnumLiteralField {
-                            attrs,
-                            member,
-                            mut colon_token,
-                            expr,
-                        },
-                        comma,
-                    ) in fields.pairs().map(|v| v.into_tuple())
-                    {
-                        tokens.append_all(attrs);
-                        if Some(member) != expr_to_member(expr).as_ref() {
-                            colon_token = Some(<Token![:]>::default());
-                        }
-                        member.to_tokens(tokens);
-                        colon_token.to_tokens(tokens);
-                        expr.to_tokens(tokens);
-                        comma.to_tokens(tokens);
-                    }
-                }
-                BraceOrParen::Paren(_) => {
-                    for (
-                        StructOrEnumLiteralField {
-                            attrs,
-                            member: _,
-                            colon_token: _,
-                            expr,
-                        },
-                        comma,
-                    ) in fields.pairs().map(|v| v.into_tuple())
-                    {
-                        tokens.append_all(attrs);
-                        expr.to_tokens(tokens);
-                        comma.to_tokens(tokens);
-                    }
-                }
-            }
-            if let Some(rest) = rest {
-                dot2_token.unwrap_or_default().to_tokens(tokens);
-                rest.to_tokens(tokens);
-            }
-        });
-    }
-}
-
-impl Visitor {
+impl Visitor<'_> {
    pub(crate) fn process_hdl_array(
        &mut self,
-        hdl_attr: HdlAttr<Nothing>,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
        mut expr_array: ExprArray,
    ) -> Expr {
-        self.require_normal_module(hdl_attr);
-        for elem in &mut expr_array.elems {
-            *elem = parse_quote_spanned! {elem.span()=>
-                ::fayalite::expr::ToExpr::to_expr(&(#elem))
-            };
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        if sim.is_some() {
+            for elem in &mut expr_array.elems {
+                *elem = parse_quote_spanned! {elem.span()=>
+                    ::fayalite::sim::value::ToSimValue::to_sim_value(&(#elem))
+                };
+            }
+            parse_quote_spanned! {span=>
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_array)
+            }
+        } else {
+            for elem in &mut expr_array.elems {
+                *elem = parse_quote_spanned! {elem.span()=>
+                    ::fayalite::expr::ToExpr::to_expr(&(#elem))
+                };
+            }
+            parse_quote_spanned! {span=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_array)
+            }
        }
-        parse_quote! {::fayalite::expr::ToExpr::to_expr(&#expr_array)}
    }
    pub(crate) fn process_hdl_repeat(
        &mut self,
-        hdl_attr: HdlAttr<Nothing>,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
        mut expr_repeat: ExprRepeat,
    ) -> Expr {
-        self.require_normal_module(hdl_attr);
        let repeated_value = &expr_repeat.expr;
-        *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
-            ::fayalite::expr::ToExpr::to_expr(&(#repeated_value))
-        };
-        parse_quote! {::fayalite::expr::ToExpr::to_expr(&#expr_repeat)}
-    }
-    pub(crate) fn process_struct_enum(
-        &mut self,
-        hdl_attr: HdlAttr<AggregateLiteralOptions>,
-        mut literal: StructOrEnumLiteral,
-    ) -> Expr {
-        let span = hdl_attr.hdl.span;
-        if let Some(rest) = literal.rest.take() {
-            self.errors
-                .error(rest, "#[hdl] struct functional update syntax not supported");
-        }
-        let mut next_var = 0usize;
-        let mut new_var = || -> Ident {
-            let retval = format_ident!("__v{}", next_var, span = span);
-            next_var += 1;
-            retval
-        };
-        let infallible_var = new_var();
-        let retval_var = new_var();
-        let mut lets = vec![];
-        let mut build_steps = vec![];
-        let literal = literal.map_field_exprs(|expr| {
-            let field_var = new_var();
-            lets.push(quote_spanned! {span=>
-                let #field_var = ::fayalite::expr::ToExpr::to_expr(&#expr);
-            });
-            parse_quote! { #field_var }
-        });
-        let Ok(StructOrEnumPath { ty, variant }) =
-            StructOrEnumPath::new(&mut self.errors, literal.path.clone(), &hdl_attr.body)
-        else {
-            return parse_quote_spanned! {span=>
-                {}
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        if sim.is_some() {
+            *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
+                ::fayalite::sim::value::ToSimValue::to_sim_value(&(#repeated_value))
            };
-        };
-        for StructOrEnumLiteralField {
-            attrs: _,
-            member,
-            colon_token: _,
-            expr,
-        } in literal.fields.iter()
-        {
-            let field_fn = format_ident!("field_{}", member);
-            build_steps.push(quote_spanned! {span=>
-                let #retval_var = #retval_var.#field_fn(#expr);
-            });
-        }
-        let check_literal = literal.map_field_exprs(|expr| {
            parse_quote_spanned! {span=>
-                ::fayalite::expr::value_from_expr_type(#expr, #infallible_var)
-            }
-        });
-        let make_expr_fn = if let Some((_variant_path, variant_ident)) = &variant {
-            let variant_fn = format_ident!("variant_{}", variant_ident);
-            build_steps.push(quote_spanned! {span=>
-                let #retval_var = #retval_var.#variant_fn();
-            });
-            quote_spanned! {span=>
-                ::fayalite::expr::make_enum_expr
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_repeat)
            }
        } else {
-            build_steps.push(quote_spanned! {span=>
-                let #retval_var = #retval_var.build();
-            });
-            quote_spanned! {span=>
-                ::fayalite::expr::make_bundle_expr
-            }
-        };
-        let variant_or_type =
-            variant.map_or_else(|| ty.clone(), |(variant_path, _variant_ident)| variant_path);
-        parse_quote_spanned! {span=>
-            {
-                #(#lets)*
-                #make_expr_fn::<#ty>(|#infallible_var| {
-                    let #retval_var = #check_literal;
-                    #[allow(unreachable_code)]
-                    match #retval_var {
-                        #variant_or_type { .. } => #retval_var,
-                        #[allow(unreachable_patterns)]
-                        _ => match #infallible_var {},
-                    }
-                }, |#retval_var| {
-                    #(#build_steps)*
-                    #retval_var
-                })
+            *expr_repeat.expr = parse_quote_spanned! {repeated_value.span()=>
+                ::fayalite::expr::ToExpr::to_expr(&(#repeated_value))
+            };
+            parse_quote_spanned! {span=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_repeat)
            }
        }
    }
    pub(crate) fn process_hdl_struct(
        &mut self,
-        hdl_attr: HdlAttr<AggregateLiteralOptions>,
-        expr_struct: ExprStruct,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_struct: ExprStruct,
    ) -> Expr {
-        self.require_normal_module(&hdl_attr);
-        self.process_struct_enum(hdl_attr, expr_struct.into())
+        let name_span = expr_struct.path.segments.last().unwrap().ident.span();
+        let ExprOptions { sim } = hdl_attr.body;
+        if sim.is_some() {
+            let ty_path = TypePath {
+                qself: expr_struct.qself.take(),
+                path: expr_struct.path,
+            };
+            expr_struct.path = parse_quote_spanned! {name_span=>
+                __SimValue::<#ty_path>
+            };
+            for field in &mut expr_struct.fields {
+                let expr = &field.expr;
+                field.expr = parse_quote_spanned! {field.member.span()=>
+                    ::fayalite::sim::value::ToSimValue::to_sim_value(&(#expr))
+                };
+            }
+            return parse_quote_spanned! {name_span=>
+                {
+                    type __SimValue<T> = <T as ::fayalite::ty::Type>::SimValue;
+                    let value: ::fayalite::sim::value::SimValue<#ty_path> = ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_struct);
+                    value
+                }
+            };
+        }
+        let builder_ident = format_ident!("__builder", span = name_span);
+        let empty_builder = if expr_struct.qself.is_some()
+            || expr_struct
+                .path
+                .segments
+                .iter()
+                .any(|seg| !seg.arguments.is_none())
+        {
+            let ty = TypePath {
+                qself: expr_struct.qself,
+                path: expr_struct.path,
+            };
+            let builder_ty = quote_spanned! {name_span=>
+                <#ty as ::fayalite::bundle::BundleType>::Builder
+            };
+            quote_spanned! {name_span=>
+                <#builder_ty as ::fayalite::__std::default::Default>::default()
+            }
+        } else {
+            let path = ExprPath {
+                attrs: vec![],
+                qself: expr_struct.qself,
+                path: expr_struct.path,
+            };
+            quote_spanned! {name_span=>
+                #path::__bundle_builder()
+            }
+        };
+        let field_calls = Vec::from_iter(expr_struct.fields.iter().map(
+            |FieldValue {
+                 attrs: _,
+                 member,
+                 colon_token: _,
+                 expr,
+             }| {
+                let field_fn = format_ident!("field_{}", member);
+                quote_spanned! {member.span()=>
+                    let #builder_ident = #builder_ident.#field_fn(#expr);
+                }
+            },
+        ));
+        parse_quote_spanned! {name_span=>
+            {
+                let #builder_ident = #empty_builder;
+                #(#field_calls)*
+                ::fayalite::expr::ToExpr::to_expr(&#builder_ident)
+            }
+        }
    }
    pub(crate) fn process_hdl_tuple(
        &mut self,
-        hdl_attr: HdlAttr<Nothing>,
-        expr_tuple: ExprTuple,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_tuple: ExprTuple,
    ) -> Expr {
-        self.require_normal_module(hdl_attr);
-        parse_quote_spanned! {expr_tuple.span()=>
-            ::fayalite::expr::ToExpr::to_expr(&#expr_tuple)
-        }
-    }
-    pub(crate) fn process_hdl_path(
-        &mut self,
-        hdl_attr: HdlAttr<Nothing>,
-        expr_path: ExprPath,
-    ) -> Expr {
-        self.require_normal_module(hdl_attr);
-        parse_quote_spanned! {expr_path.span()=>
-            ::fayalite::expr::ToExpr::to_expr(&#expr_path)
+        let ExprOptions { sim } = hdl_attr.body;
+        if sim.is_some() {
+            for element in &mut expr_tuple.elems {
+                *element = parse_quote_spanned! {element.span()=>
+                    &(#element)
+                };
+            }
+            parse_quote_spanned! {expr_tuple.span()=>
+                ::fayalite::sim::value::ToSimValue::into_sim_value(#expr_tuple)
+            }
+        } else {
+            parse_quote_spanned! {expr_tuple.span()=>
+                ::fayalite::expr::ToExpr::to_expr(&#expr_tuple)
+            }
        }
    }
    pub(crate) fn process_hdl_call(
        &mut self,
-        hdl_attr: HdlAttr<AggregateLiteralOptions>,
-        expr_call: ExprCall,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_call: ExprCall,
    ) -> Expr {
-        self.require_normal_module(&hdl_attr);
-        let ExprCall {
-            attrs: mut literal_attrs,
-            func,
-            paren_token,
-            args,
-        } = expr_call;
-        let mut path_expr = *func;
-        let path = loop {
-            break match path_expr {
-                Expr::Group(ExprGroup {
-                    attrs,
-                    group_token: _,
-                    expr,
-                }) => {
-                    literal_attrs.extend(attrs);
-                    path_expr = *expr;
-                    continue;
+        let span = hdl_attr.kw.span;
+        let mut func = &mut *expr_call.func;
+        let EnumPath {
+            variant_path: _,
+            enum_path,
+            variant_name,
+        } = loop {
+            match func {
+                Expr::Group(ExprGroup { expr, .. }) | Expr::Paren(ExprParen { expr, .. }) => {
+                    func = &mut **expr;
                }
-                Expr::Path(ExprPath { attrs, qself, path }) => {
-                    literal_attrs.extend(attrs);
-                    TypePath { qself, path }
+                Expr::Path(_) => {
+                    let Expr::Path(ExprPath { attrs, qself, path }) =
+                        mem::replace(func, Expr::PLACEHOLDER)
+                    else {
+                        unreachable!();
+                    };
+                    match parse_enum_path(TypePath { qself, path }) {
+                        Ok(path) => break path,
+                        Err(path) => {
+                            self.errors.error(&path, "unsupported enum variant path");
+                            let TypePath { qself, path } = path;
+                            *func = ExprPath { attrs, qself, path }.into();
+                            return expr_call.into();
+                        }
+                    }
                }
                _ => {
-                    self.errors.error(&path_expr, "missing tuple struct's name");
-                    return parse_quote_spanned! {path_expr.span()=>
-                        {}
-                    };
+                    self.errors.error(
+                        &expr_call.func,
+                        "#[hdl] function call -- function must be a possibly-parenthesized path",
+                    );
+                    return expr_call.into();
                }
-            };
+            }
        };
-        let fields = args
-            .into_pairs()
-            .enumerate()
-            .map(|(index, p)| {
-                let (expr, comma) = p.into_tuple();
-                let mut index = Index::from(index);
-                index.span = hdl_attr.hdl.span;
-                Pair::new(
-                    StructOrEnumLiteralField {
-                        attrs: vec![],
-                        member: Member::Unnamed(index),
-                        colon_token: None,
-                        expr,
-                    },
-                    comma,
-                )
-            })
-            .collect();
-        self.process_struct_enum(
+        self.process_hdl_method_call(
            hdl_attr,
-            StructOrEnumLiteral {
-                attrs: literal_attrs,
-                path,
-                brace_or_paren: BraceOrParen::Paren(paren_token),
-                fields,
-                dot2_token: None,
-                rest: None,
+            ExprMethodCall {
+                attrs: expr_call.attrs,
+                receiver: parse_quote_spanned! {span=>
+                    <#enum_path as ::fayalite::ty::StaticType>::TYPE
+                },
+                dot_token: Token![.](span),
+                method: variant_name,
+                turbofish: None,
+                paren_token: expr_call.paren_token,
+                args: expr_call.args,
            },
        )
    }
+    pub(crate) fn process_hdl_method_call(
+        &mut self,
+        hdl_attr: HdlAttr<ExprOptions, kw::hdl>,
+        mut expr_method_call: ExprMethodCall,
+    ) -> Expr {
+        let ExprOptions { sim } = hdl_attr.body;
+        let span = hdl_attr.kw.span;
+        // remove any number of groups and up to one paren
+        let mut receiver = &mut *expr_method_call.receiver;
+        let mut has_group = false;
+        let receiver = loop {
+            match receiver {
+                Expr::Group(ExprGroup { expr, .. }) => {
+                    has_group = true;
+                    receiver = expr;
+                }
+                Expr::Paren(ExprParen { expr, .. }) => break &mut **expr,
+                receiver @ Expr::Path(_) => break receiver,
+                _ => {
+                    if !has_group {
+                        self.errors.error(
+                            &expr_method_call.receiver,
+                            "#[hdl] on a method call needs parenthesized receiver",
+                        );
+                    }
+                    break &mut *expr_method_call.receiver;
+                }
+            }
+        };
+        let func = if sim.is_some() {
+            parse_quote_spanned! {span=>
+                ::fayalite::enum_::enum_type_to_sim_builder
+            }
+        } else {
+            parse_quote_spanned! {span=>
+                ::fayalite::enum_::assert_is_enum_type
+            }
+        };
+        *expr_method_call.receiver = ExprCall {
+            attrs: vec![],
+            func,
+            paren_token: Paren(span),
+            args: Punctuated::from_iter([mem::replace(receiver, Expr::PLACEHOLDER)]),
+        }
+        .into();
+        expr_method_call.into()
+    }
 }
--- a/crates/fayalite-proc-macros-impl/src/module/transform_body/expand_match.rs
+++ b/crates/fayalite-proc-macros-impl/src/module/transform_body/expand_match.rs
--- a/crates/fayalite-proc-macros-impl/src/process_cfg.rs
+++ b/crates/fayalite-proc-macros-impl/src/process_cfg.rs
--- a/crates/fayalite-proc-macros-impl/src/value_derive_common.rs
+++ b/crates/fayalite-proc-macros-impl/src/value_derive_common.rs
@ -1,761 +0,0 @@
-// SPDX-License-Identifier: LGPL-3.0-or-later
-// See Notices.txt for copyright information
-use crate::{fold::impl_fold, kw, Errors, HdlAttr};
-use proc_macro2::{Span, TokenStream};
-use quote::{format_ident, quote, quote_spanned, ToTokens};
-use std::collections::{BTreeMap, HashMap, HashSet};
-use syn::{
-    fold::{fold_generics, Fold},
-    parse::{Parse, ParseStream},
-    parse_quote, parse_quote_spanned,
-    punctuated::Punctuated,
-    spanned::Spanned,
-    token::{Brace, Paren, Where},
-    Block, ConstParam, Expr, Field, Fields, FieldsNamed, FieldsUnnamed, GenericParam, Generics,
-    Ident, Index, ItemImpl, Lifetime, LifetimeParam, Member, Path, Token, Type, TypeParam,
-    TypePath, Visibility, WhereClause, WherePredicate,
-};
-
-#[derive(Clone, Debug)]
-pub(crate) struct Bounds(pub(crate) Punctuated<WherePredicate, Token![,]>);
-
-impl_fold! {
-    struct Bounds<>(Punctuated<WherePredicate, Token![,]>);
-}
-
-impl Parse for Bounds {
-    fn parse(input: ParseStream) -> syn::Result<Self> {
-        Ok(Bounds(Punctuated::parse_terminated(input)?))
-    }
-}
-
-impl From<Option<WhereClause>> for Bounds {
-    fn from(value: Option<WhereClause>) -> Self {
-        Self(value.map_or_else(Punctuated::new, |v| v.predicates))
-    }
-}
-
-impl ToTokens for Bounds {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        self.0.to_tokens(tokens)
-    }
-}
-
-#[derive(Debug, Clone)]
-pub(crate) struct ParsedField<O> {
-    pub(crate) options: HdlAttr<O>,
-    pub(crate) vis: Visibility,
-    pub(crate) name: Member,
-    pub(crate) ty: Type,
-}
-
-impl<O> ParsedField<O> {
-    pub(crate) fn var_name(&self) -> Ident {
-        format_ident!("__v_{}", self.name)
-    }
-}
-
-pub(crate) fn get_field_name(
-    index: usize,
-    name: Option<Ident>,
-    ty_span: impl FnOnce() -> Span,
-) -> Member {
-    match name {
-        Some(name) => Member::Named(name),
-        None => Member::Unnamed(Index {
-            index: index as _,
-            span: ty_span(),
-        }),
-    }
-}
-
-pub(crate) fn get_field_names(fields: &Fields) -> impl Iterator<Item = Member> + '_ {
-    fields
-        .iter()
-        .enumerate()
-        .map(|(index, field)| get_field_name(index, field.ident.clone(), || field.ty.span()))
-}
-
-impl<O: Parse + Default> ParsedField<O> {
-    pub(crate) fn parse_fields(
-        errors: &mut Errors,
-        fields: &mut Fields,
-        in_enum: bool,
-    ) -> (FieldsKind, Vec<ParsedField<O>>) {
-        let mut unit_fields = Punctuated::new();
-        let (fields_kind, fields) = match fields {
-            Fields::Named(fields) => (FieldsKind::Named(fields.brace_token), &mut fields.named),
-            Fields::Unnamed(fields) => {
-                (FieldsKind::Unnamed(fields.paren_token), &mut fields.unnamed)
-            }
-            Fields::Unit => (FieldsKind::Unit, &mut unit_fields),
-        };
-        let fields = fields
-            .iter_mut()
-            .enumerate()
-            .map(|(index, field)| {
-                let options = errors
-                    .unwrap_or_default(HdlAttr::parse_and_take_attr(&mut field.attrs))
-                    .unwrap_or_default();
-                let name = get_field_name(index, field.ident.clone(), || field.ty.span());
-                if in_enum && !matches!(field.vis, Visibility::Inherited) {
-                    errors.error(&field.vis, "field visibility not allowed in enums");
-                }
-                ParsedField {
-                    options,
-                    vis: field.vis.clone(),
-                    name,
-                    ty: field.ty.clone(),
-                }
-            })
-            .collect();
-        (fields_kind, fields)
-    }
-}
-
-#[derive(Copy, Clone, Debug)]
-pub(crate) enum FieldsKind {
-    Unit,
-    Named(Brace),
-    Unnamed(Paren),
-}
-
-impl FieldsKind {
-    pub(crate) fn into_fields_named(
-        brace_token: Brace,
-        fields: impl IntoIterator<Item = syn::Field>,
-    ) -> Fields {
-        Fields::Named(FieldsNamed {
-            brace_token,
-            named: Punctuated::from_iter(fields),
-        })
-    }
-    pub(crate) fn into_fields_unnamed(
-        paren_token: Paren,
-        fields: impl IntoIterator<Item = syn::Field>,
-    ) -> Fields {
-        Fields::Unnamed(FieldsUnnamed {
-            paren_token,
-            unnamed: Punctuated::from_iter(fields),
-        })
-    }
-    pub(crate) fn into_fields(self, fields: impl IntoIterator<Item = syn::Field>) -> Fields {
-        match self {
-            FieldsKind::Unit => {
-                let mut fields = fields.into_iter().peekable();
-                let Some(first_field) = fields.peek() else {
-                    return Fields::Unit;
-                };
-                if first_field.ident.is_some() {
-                    Self::into_fields_named(Default::default(), fields)
-                } else {
-                    Self::into_fields_unnamed(Default::default(), fields)
-                }
-            }
-            FieldsKind::Named(brace_token) => Self::into_fields_named(brace_token, fields),
-            FieldsKind::Unnamed(paren_token) => Self::into_fields_unnamed(paren_token, fields),
-        }
-    }
-}
-
-pub(crate) fn get_target(target: &Option<(kw::target, Paren, Path)>, item_ident: &Ident) -> Path {
-    match target {
-        Some((_, _, target)) => target.clone(),
-        None => item_ident.clone().into(),
-    }
-}
-
-pub(crate) struct ValueDeriveGenerics {
-    pub(crate) generics: Generics,
-    pub(crate) static_type_generics: Generics,
-}
-
-impl ValueDeriveGenerics {
-    pub(crate) fn get(mut generics: Generics, where_: &Option<(Where, Paren, Bounds)>) -> Self {
-        let mut static_type_generics = generics.clone();
-        if let Some((_, _, bounds)) = where_ {
-            generics
-                .make_where_clause()
-                .predicates
-                .extend(bounds.0.iter().cloned());
-            static_type_generics
-                .where_clause
-                .clone_from(&generics.where_clause);
-        } else {
-            let type_params = Vec::from_iter(generics.type_params().map(|v| v.ident.clone()));
-            let predicates = &mut generics.make_where_clause().predicates;
-            let static_type_predicates = &mut static_type_generics.make_where_clause().predicates;
-            for type_param in type_params {
-                predicates.push(parse_quote! {#type_param: ::fayalite::ty::Value<Type: ::fayalite::ty::Type<Value = #type_param>>});
-                static_type_predicates
-                    .push(parse_quote! {#type_param: ::fayalite::ty::StaticValue});
-            }
-        }
-        Self {
-            generics,
-            static_type_generics,
-        }
-    }
-}
-
-pub(crate) fn derive_clone_hash_eq_partialeq_for_struct<Name: ToTokens>(
-    the_struct_ident: &Ident,
-    generics: &Generics,
-    field_names: &[Name],
-) -> TokenStream {
-    let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
-    quote! {
-        #[automatically_derived]
-        impl #impl_generics ::fayalite::__std::clone::Clone for #the_struct_ident #type_generics
-        #where_clause
-        {
-            fn clone(&self) -> Self {
-                Self {
-                    #(#field_names: ::fayalite::__std::clone::Clone::clone(&self.#field_names),)*
-                }
-            }
-        }
-
-        #[automatically_derived]
-        impl #impl_generics ::fayalite::__std::hash::Hash for #the_struct_ident #type_generics
-        #where_clause
-        {
-            #[allow(unused_variables)]
-            fn hash<__H: ::fayalite::__std::hash::Hasher>(&self, hasher: &mut __H) {
-                #(::fayalite::__std::hash::Hash::hash(&self.#field_names, hasher);)*
-            }
-        }
-
-        #[automatically_derived]
-        impl #impl_generics ::fayalite::__std::cmp::Eq for #the_struct_ident #type_generics
-        #where_clause
-        {
-        }
-
-        #[automatically_derived]
-        impl #impl_generics ::fayalite::__std::cmp::PartialEq for #the_struct_ident #type_generics
-        #where_clause
-        {
-            #[allow(unused_variables)]
-            #[allow(clippy::nonminimal_bool)]
-            fn eq(&self, other: &Self) -> ::fayalite::__std::primitive::bool {
-                true #(&& ::fayalite::__std::cmp::PartialEq::eq(
-                    &self.#field_names,
-                    &other.#field_names,
-                ))*
-            }
-        }
-    }
-}
-
-pub(crate) fn append_field(fields: &mut Fields, mut field: Field) -> Member {
-    let ident = field.ident.clone().expect("ident is supplied");
-    match fields {
-        Fields::Named(FieldsNamed { named, .. }) => {
-            named.push(field);
-            Member::Named(ident)
-        }
-        Fields::Unnamed(FieldsUnnamed { unnamed, .. }) => {
-            field.ident = None;
-            field.colon_token = None;
-            let index = unnamed.len();
-            unnamed.push(field);
-            Member::Unnamed(index.into())
-        }
-        Fields::Unit => {
-            *fields = Fields::Named(FieldsNamed {
-                brace_token: Default::default(),
-                named: Punctuated::from_iter([field]),
-            });
-            Member::Named(ident)
-        }
-    }
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct BuilderField {
-    pub(crate) names: HashSet<Member>,
-    pub(crate) mapped_value: Expr,
-    pub(crate) mapped_type: Type,
-    pub(crate) where_clause: Option<WhereClause>,
-    pub(crate) builder_field_name: Ident,
-    pub(crate) type_param: Ident,
-}
-
-#[derive(Debug)]
-pub(crate) struct Builder {
-    struct_name: Ident,
-    vis: Visibility,
-    fields: BTreeMap<String, BuilderField>,
-}
-
-#[derive(Debug)]
-pub(crate) struct BuilderWithFields {
-    struct_name: Ident,
-    vis: Visibility,
-    phantom_type_param: Ident,
-    phantom_type_field: Ident,
-    fields: Vec<(String, BuilderField)>,
-}
-
-impl Builder {
-    pub(crate) fn new(struct_name: Ident, vis: Visibility) -> Self {
-        Self {
-            struct_name,
-            vis,
-            fields: BTreeMap::new(),
-        }
-    }
-    pub(crate) fn insert_field(
-        &mut self,
-        name: Member,
-        map_value: impl FnOnce(&Ident) -> Expr,
-        map_type: impl FnOnce(&Ident) -> Type,
-        where_clause: impl FnOnce(&Ident) -> Option<WhereClause>,
-    ) {
-        self.fields
-            .entry(name.to_token_stream().to_string())
-            .or_insert_with_key(|name| {
-                let builder_field_name =
-                    format_ident!("field_{}", name, span = self.struct_name.span());
-                let type_param = format_ident!("__T_{}", name, span = self.struct_name.span());
-                BuilderField {
-                    names: HashSet::new(),
-                    mapped_value: map_value(&builder_field_name),
-                    mapped_type: map_type(&type_param),
-                    where_clause: where_clause(&type_param),
-                    builder_field_name,
-                    type_param,
-                }
-            })
-            .names
-            .insert(name);
-    }
-    pub(crate) fn finish_filling_in_fields(self) -> BuilderWithFields {
-        let Self {
-            struct_name,
-            vis,
-            fields,
-        } = self;
-        let fields = Vec::from_iter(fields);
-        BuilderWithFields {
-            phantom_type_param: Ident::new("__Phantom", struct_name.span()),
-            phantom_type_field: Ident::new("__phantom", struct_name.span()),
-            struct_name,
-            vis,
-            fields,
-        }
-    }
-}
-
-impl BuilderWithFields {
-    pub(crate) fn get_field(&self, name: &Member) -> Option<(usize, &BuilderField)> {
-        let index = self
-            .fields
-            .binary_search_by_key(&&*name.to_token_stream().to_string(), |v| &*v.0)
-            .ok()?;
-        Some((index, &self.fields[index].1))
-    }
-    pub(crate) fn ty(
-        &self,
-        specified_fields: impl IntoIterator<Item = (Member, Type)>,
-        phantom_type: Option<&Type>,
-        other_fields_are_any_type: bool,
-    ) -> TypePath {
-        let Self {
-            struct_name,
-            vis: _,
-            phantom_type_param,
-            phantom_type_field: _,
-            fields,
-        } = self;
-        let span = struct_name.span();
-        let mut arguments =
-            Vec::from_iter(fields.iter().map(|(_, BuilderField { type_param, .. })| {
-                if other_fields_are_any_type {
-                    parse_quote_spanned! {span=>
-                        #type_param
-                    }
-                } else {
-                    parse_quote_spanned! {span=>
-                        ()
-                    }
-                }
-            }));
-        for (name, ty) in specified_fields {
-            let Some((index, _)) = self.get_field(&name) else {
-                panic!("field not found: {}", name.to_token_stream());
-            };
-            arguments[index] = ty;
-        }
-        let phantom_type_param = phantom_type.is_none().then_some(phantom_type_param);
-        parse_quote_spanned! {span=>
-            #struct_name::<#phantom_type_param #phantom_type #(, #arguments)*>
-        }
-    }
-    pub(crate) fn append_generics(
-        &self,
-        specified_fields: impl IntoIterator<Item = Member>,
-        has_phantom_type_param: bool,
-        other_fields_are_any_type: bool,
-        generics: &mut Generics,
-    ) {
-        let Self {
-            struct_name: _,
-            vis: _,
-            phantom_type_param,
-            phantom_type_field: _,
-            fields,
-        } = self;
-        if has_phantom_type_param {
-            generics.params.push(GenericParam::from(TypeParam::from(
-                phantom_type_param.clone(),
-            )));
-        }
-        if !other_fields_are_any_type {
-            return;
-        }
-        let mut type_params = Vec::from_iter(
-            fields
-                .iter()
-                .map(|(_, BuilderField { type_param, .. })| Some(type_param)),
-        );
-        for name in specified_fields {
-            let Some((index, _)) = self.get_field(&name) else {
-                panic!("field not found: {}", name.to_token_stream());
-            };
-            type_params[index] = None;
-        }
-        generics.params.extend(
-            type_params
-                .into_iter()
-                .filter_map(|v| Some(GenericParam::from(TypeParam::from(v?.clone())))),
-        );
-    }
-    pub(crate) fn make_build_method(
-        &self,
-        build_fn_name: &Ident,
-        specified_fields: impl IntoIterator<Item = (Member, Type)>,
-        generics: &Generics,
-        phantom_type: &Type,
-        return_ty: &Type,
-        mut body: Block,
-    ) -> ItemImpl {
-        let Self {
-            struct_name,
-            vis,
-            phantom_type_param: _,
-            phantom_type_field,
-            fields,
-        } = self;
-        let span = struct_name.span();
-        let field_names = Vec::from_iter(fields.iter().map(|v| &v.1.builder_field_name));
-        let (impl_generics, _type_generics, where_clause) = generics.split_for_impl();
-        let empty_arg = parse_quote_spanned! {span=>
-            ()
-        };
-        let mut ty_arguments = vec![empty_arg; fields.len()];
-        let empty_field_pat = quote_spanned! {span=>
-            : _
-        };
-        let mut field_pats = vec![Some(empty_field_pat); fields.len()];
-        for (name, ty) in specified_fields {
-            let Some((index, _)) = self.get_field(&name) else {
-                panic!("field not found: {}", name.to_token_stream());
-            };
-            ty_arguments[index] = ty;
-            field_pats[index] = None;
-        }
-        body.stmts.insert(
-            0,
-            parse_quote_spanned! {span=>
-                let Self {
-                    #(#field_names #field_pats,)*
-                    #phantom_type_field: _,
-                } = self;
-            },
-        );
-        parse_quote_spanned! {span=>
-            #[automatically_derived]
-            impl #impl_generics #struct_name<#phantom_type #(, #ty_arguments)*>
-            #where_clause
-            {
-                #[allow(non_snake_case, dead_code)]
-                #vis fn #build_fn_name(self) -> #return_ty
-                #body
-            }
-        }
-    }
-}
-
-impl ToTokens for BuilderWithFields {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        let Self {
-            struct_name,
-            vis,
-            phantom_type_param,
-            phantom_type_field,
-            fields,
-        } = self;
-        let span = struct_name.span();
-        let mut any_generics = Generics::default();
-        self.append_generics([], true, true, &mut any_generics);
-        let empty_ty = self.ty([], None, false);
-        let field_names = Vec::from_iter(fields.iter().map(|v| &v.1.builder_field_name));
-        let field_type_params = Vec::from_iter(fields.iter().map(|v| &v.1.type_param));
-        quote_spanned! {span=>
-            #[allow(non_camel_case_types)]
-            #[non_exhaustive]
-            #vis struct #struct_name #any_generics {
-                #(#field_names: #field_type_params,)*
-                #phantom_type_field: ::fayalite::__std::marker::PhantomData<#phantom_type_param>,
-            }
-
-            #[automatically_derived]
-            impl<#phantom_type_param> #empty_ty {
-                fn new() -> Self {
-                    Self {
-                        #(#field_names: (),)*
-                        #phantom_type_field: ::fayalite::__std::marker::PhantomData,
-                    }
-                }
-            }
-        }
-        .to_tokens(tokens);
-        for (field_index, (_, field)) in self.fields.iter().enumerate() {
-            let initial_fields = &fields[..field_index];
-            let final_fields = &fields[field_index..][1..];
-            let initial_type_params =
-                Vec::from_iter(initial_fields.iter().map(|v| &v.1.type_param));
-            let final_type_params = Vec::from_iter(final_fields.iter().map(|v| &v.1.type_param));
-            let initial_field_names =
-                Vec::from_iter(initial_fields.iter().map(|v| &v.1.builder_field_name));
-            let final_field_names =
-                Vec::from_iter(final_fields.iter().map(|v| &v.1.builder_field_name));
-            let BuilderField {
-                names: _,
-                mapped_value,
-                mapped_type,
-                where_clause,
-                builder_field_name,
-                type_param,
-            } = field;
-            quote_spanned! {span=>
-                #[automatically_derived]
-                #[allow(non_camel_case_types, dead_code)]
-                impl<#phantom_type_param #(, #initial_type_params)* #(, #final_type_params)*>
-                    #struct_name<
-                        #phantom_type_param,
-                        #(#initial_type_params,)*
-                        (), #(#final_type_params,)*
-                    >
-                {
-                    #vis fn #builder_field_name<#type_param>(
-                        self,
-                        #builder_field_name: #type_param,
-                    ) -> #struct_name<
-                            #phantom_type_param,
-                            #(#initial_type_params,)*
-                            #mapped_type,
-                            #(#final_type_params,)*
-                        >
-                    #where_clause
-                    {
-                        let Self {
-                            #(#initial_field_names,)*
-                            #builder_field_name: (),
-                            #(#final_field_names,)*
-                            #phantom_type_field: _,
-                        } = self;
-                        let #builder_field_name = #mapped_value;
-                        #struct_name {
-                            #(#field_names,)*
-                            #phantom_type_field: ::fayalite::__std::marker::PhantomData,
-                        }
-                    }
-                }
-            }
-            .to_tokens(tokens);
-        }
-    }
-}
-
-pub(crate) struct MapIdents {
-    pub(crate) map: HashMap<Ident, Ident>,
-}
-
-impl Fold for &MapIdents {
-    fn fold_ident(&mut self, i: Ident) -> Ident {
-        self.map.get(&i).cloned().unwrap_or(i)
-    }
-}
-
-pub(crate) struct DupGenerics<M> {
-    pub(crate) combined: Generics,
-    pub(crate) maps: M,
-}
-
-pub(crate) fn merge_punctuated<T, P: Default>(
-    target: &mut Punctuated<T, P>,
-    source: Punctuated<T, P>,
-    make_punct: impl FnOnce() -> P,
-) {
-    if source.is_empty() {
-        return;
-    }
-    if target.is_empty() {
-        *target = source;
-        return;
-    }
-    if !target.trailing_punct() {
-        target.push_punct(make_punct());
-    }
-    target.extend(source.into_pairs());
-}
-
-pub(crate) fn merge_generics(target: &mut Generics, source: Generics) {
-    let Generics {
-        lt_token,
-        params,
-        gt_token,
-        where_clause,
-    } = source;
-    let span = lt_token.map(|v| v.span).unwrap_or_else(|| params.span());
-    target.lt_token = target.lt_token.or(lt_token);
-    merge_punctuated(&mut target.params, params, || Token![,](span));
-    target.gt_token = target.gt_token.or(gt_token);
-    if let Some(where_clause) = where_clause {
-        if let Some(target_where_clause) = &mut target.where_clause {
-            let WhereClause {
-                where_token,
-                predicates,
-            } = where_clause;
-            let span = where_token.span;
-            target_where_clause.where_token = where_token;
-            merge_punctuated(&mut target_where_clause.predicates, predicates, || {
-                Token![,](span)
-            });
-        } else {
-            target.where_clause = Some(where_clause);
-        }
-    }
-}
-
-impl DupGenerics<Vec<MapIdents>> {
-    pub(crate) fn new_dyn(generics: &Generics, count: usize) -> Self {
-        let mut maps = Vec::from_iter((0..count).map(|_| MapIdents {
-            map: HashMap::new(),
-        }));
-        for param in &generics.params {
-            let (GenericParam::Lifetime(LifetimeParam {
-                lifetime: Lifetime { ident, .. },
-                ..
-            })
-            | GenericParam::Type(TypeParam { ident, .. })
-            | GenericParam::Const(ConstParam { ident, .. })) = param;
-            for (i, map_idents) in maps.iter_mut().enumerate() {
-                map_idents
-                    .map
-                    .insert(ident.clone(), format_ident!("__{}_{}", ident, i));
-            }
-        }
-        let mut combined = Generics::default();
-        for map_idents in maps.iter() {
-            merge_generics(
-                &mut combined,
-                fold_generics(&mut { map_idents }, generics.clone()),
-            );
-        }
-        Self { combined, maps }
-    }
-}
-
-impl<const COUNT: usize> DupGenerics<[MapIdents; COUNT]> {
-    pub(crate) fn new(generics: &Generics) -> Self {
-        let DupGenerics { combined, maps } = DupGenerics::new_dyn(generics, COUNT);
-        Self {
-            combined,
-            maps: maps.try_into().ok().unwrap(),
-        }
-    }
-}
-
-pub(crate) fn add_where_predicate(
-    target: &mut Generics,
-    span: Span,
-    where_predicate: WherePredicate,
-) {
-    let WhereClause {
-        where_token: _,
-        predicates,
-    } = target.where_clause.get_or_insert_with(|| WhereClause {
-        where_token: Token![where](span),
-        predicates: Punctuated::new(),
-    });
-    if !predicates.empty_or_trailing() {
-        predicates.push_punct(Token![,](span));
-    }
-    predicates.push_value(where_predicate);
-}
-
-pub(crate) fn make_connect_impl(
-    connect_inexact: Option<(crate::kw::connect_inexact,)>,
-    generics: &Generics,
-    ty_ident: &Ident,
-    field_types: impl IntoIterator<Item = Type>,
-) -> TokenStream {
-    let span = ty_ident.span();
-    let impl_generics;
-    let combined_generics;
-    let where_clause;
-    let lhs_generics;
-    let lhs_type_generics;
-    let rhs_generics;
-    let rhs_type_generics;
-    if connect_inexact.is_some() {
-        let DupGenerics {
-            mut combined,
-            maps: [lhs_map, rhs_map],
-        } = DupGenerics::new(generics);
-        for field_type in field_types {
-            let lhs_type = (&lhs_map).fold_type(field_type.clone());
-            let rhs_type = (&rhs_map).fold_type(field_type);
-            add_where_predicate(
-                &mut combined,
-                span,
-                parse_quote_spanned! {span=>
-                    #lhs_type: ::fayalite::ty::Connect<#rhs_type>
-                },
-            );
-        }
-        combined_generics = combined;
-        (impl_generics, _, where_clause) = combined_generics.split_for_impl();
-        lhs_generics = (&lhs_map).fold_generics(generics.clone());
-        (_, lhs_type_generics, _) = lhs_generics.split_for_impl();
-        rhs_generics = (&rhs_map).fold_generics(generics.clone());
-        (_, rhs_type_generics, _) = rhs_generics.split_for_impl();
-    } else {
-        let mut generics = generics.clone();
-        for field_type in field_types {
-            add_where_predicate(
-                &mut generics,
-                span,
-                parse_quote_spanned! {span=>
-                    #field_type: ::fayalite::ty::Connect<#field_type>
-                },
-            );
-        }
-        combined_generics = generics;
-        (impl_generics, lhs_type_generics, where_clause) = combined_generics.split_for_impl();
-        rhs_type_generics = lhs_type_generics.clone();
-    }
-    quote_spanned! {span=>
-        #[automatically_derived]
-        #[allow(non_camel_case_types)]
-        impl #impl_generics ::fayalite::ty::Connect<#ty_ident #rhs_type_generics>
-            for #ty_ident #lhs_type_generics
-        #where_clause
-        {
-        }
-    }
-}
--- a/crates/fayalite-proc-macros-impl/src/value_derive_enum.rs
+++ b/crates/fayalite-proc-macros-impl/src/value_derive_enum.rs
@ -1,975 +0,0 @@
-// SPDX-License-Identifier: LGPL-3.0-or-later
-// See Notices.txt for copyright information
-use crate::{
-    value_derive_common::{
-        append_field, derive_clone_hash_eq_partialeq_for_struct, get_field_names, get_target,
-        make_connect_impl, Bounds, Builder, FieldsKind, ParsedField, ValueDeriveGenerics,
-    },
-    value_derive_struct::{self, ParsedStruct, ParsedStructNames, StructOptions},
-    Errors, HdlAttr,
-};
-use proc_macro2::TokenStream;
-use quote::{format_ident, quote, quote_spanned, ToTokens};
-use syn::{
-    parse_quote, parse_quote_spanned, punctuated::Punctuated, spanned::Spanned, token::Brace,
-    Field, FieldMutability, Fields, FieldsNamed, Generics, Ident, Index, ItemEnum, ItemStruct,
-    Member, Path, Token, Type, Variant, Visibility,
-};
-
-crate::options! {
-    #[options = EnumOptions]
-    enum EnumOption {
-        OutlineGenerated(outline_generated),
-        ConnectInexact(connect_inexact),
-        Bounds(where_, Bounds),
-        Target(target, Path),
-    }
-}
-
-crate::options! {
-    #[options = VariantOptions]
-    enum VariantOption {}
-}
-
-crate::options! {
-    #[options = FieldOptions]
-    enum FieldOption {}
-}
-
-enum VariantValue {
-    None,
-    Direct {
-        value_type: Type,
-    },
-    Struct {
-        value_struct: ItemStruct,
-        parsed_struct: ParsedStruct,
-    },
-}
-
-impl VariantValue {
-    fn is_none(&self) -> bool {
-        matches!(self, Self::None)
-    }
-    fn value_ty(&self) -> Option<Type> {
-        match self {
-            VariantValue::None => None,
-            VariantValue::Direct { value_type } => Some(value_type.clone()),
-            VariantValue::Struct { value_struct, .. } => {
-                let (_, type_generics, _) = value_struct.generics.split_for_impl();
-                let ident = &value_struct.ident;
-                Some(parse_quote! { #ident #type_generics })
-            }
-        }
-    }
-}
-
-struct ParsedVariant {
-    options: HdlAttr<VariantOptions>,
-    ident: Ident,
-    fields_kind: FieldsKind,
-    fields: Vec<ParsedField<FieldOptions>>,
-    value: VariantValue,
-}
-
-impl ParsedVariant {
-    fn parse(
-        errors: &mut Errors,
-        variant: Variant,
-        enum_options: &EnumOptions,
-        enum_vis: &Visibility,
-        enum_ident: &Ident,
-        enum_generics: &Generics,
-    ) -> Self {
-        let target = get_target(&enum_options.target, enum_ident);
-        let Variant {
-            mut attrs,
-            ident,
-            fields,
-            discriminant,
-        } = variant;
-        if let Some((eq, _)) = discriminant {
-            errors.error(eq, "#[derive(Value)]: discriminants not allowed");
-        }
-        let variant_options = errors
-            .unwrap_or_default(HdlAttr::parse_and_take_attr(&mut attrs))
-            .unwrap_or_default();
-        let (fields_kind, parsed_fields) =
-            ParsedField::parse_fields(errors, &mut fields.clone(), true);
-        let value = match (&fields_kind, &*parsed_fields) {
-            (FieldsKind::Unit, _) => VariantValue::None,
-            (
-                FieldsKind::Unnamed(_),
-                [ParsedField {
-                    options,
-                    vis: _,
-                    name: Member::Unnamed(Index { index: 0, span: _ }),
-                    ty,
-                }],
-            ) => {
-                let FieldOptions {} = options.body;
-                VariantValue::Direct {
-                    value_type: ty.clone(),
-                }
-            }
-            _ => {
-                let variant_value_struct_ident =
-                    format_ident!("__{}__{}", enum_ident, ident, span = ident.span());
-                let variant_type_struct_ident =
-                    format_ident!("__{}__{}__Type", enum_ident, ident, span = ident.span());
-                let mut value_struct_fields = fields.clone();
-                let (_, type_generics, _) = enum_generics.split_for_impl();
-                append_field(
-                    &mut value_struct_fields,
-                    Field {
-                        attrs: vec![HdlAttr::from(value_derive_struct::FieldOptions {
-                            flip: None,
-                            skip: Some(Default::default()),
-                        })
-                        .to_attr()],
-                        vis: enum_vis.clone(),
-                        mutability: FieldMutability::None,
-                        ident: Some(Ident::new("__phantom", ident.span())),
-                        colon_token: None,
-                        ty: parse_quote_spanned! {ident.span()=>
-                            ::fayalite::__std::marker::PhantomData<#target #type_generics>
-                        },
-                    },
-                );
-                let (value_struct_fields_kind, value_struct_parsed_fields) =
-                    ParsedField::parse_fields(errors, &mut value_struct_fields, false);
-                let value_struct = ItemStruct {
-                    attrs: vec![parse_quote! { #[allow(non_camel_case_types)] }],
-                    vis: enum_vis.clone(),
-                    struct_token: Token![struct](ident.span()),
-                    ident: variant_value_struct_ident.clone(),
-                    generics: enum_generics.clone(),
-                    fields: value_struct_fields,
-                    semi_token: None,
-                };
-                VariantValue::Struct {
-                    value_struct,
-                    parsed_struct: ParsedStruct {
-                        options: StructOptions {
-                            outline_generated: None,
-                            static_: Some(Default::default()),
-                            where_: Some((
-                                Default::default(),
-                                Default::default(),
-                                ValueDeriveGenerics::get(
-                                    enum_generics.clone(),
-                                    &enum_options.where_,
-                                )
-                                .static_type_generics
-                                .where_clause
-                                .into(),
-                            )),
-                            target: None,
-                            connect_inexact: enum_options.connect_inexact,
-                        }
-                        .into(),
-                        vis: enum_vis.clone(),
-                        struct_token: Default::default(),
-                        generics: enum_generics.clone(),
-                        fields_kind: value_struct_fields_kind,
-                        fields: value_struct_parsed_fields,
-                        semi_token: None, // it will fill in the semicolon if needed
-                        skip_check_fields: true,
-                        names: ParsedStructNames {
-                            ident: variant_value_struct_ident.clone(),
-                            type_struct_debug_ident: Some(format!("{enum_ident}::{ident}::Type")),
-                            type_struct_ident: variant_type_struct_ident,
-                            match_variant_ident: None,
-                            builder_struct_ident: None,
-                            mask_match_variant_ident: None,
-                            mask_type_ident: None,
-                            mask_type_debug_ident: Some(format!(
-                                "AsMask<{enum_ident}::{ident}>::Type"
-                            )),
-                            mask_value_ident: None,
-                            mask_value_debug_ident: Some(format!("AsMask<{enum_ident}::{ident}>")),
-                            mask_builder_struct_ident: None,
-                        },
-                    },
-                }
-            }
-        };
-        ParsedVariant {
-            options: variant_options,
-            ident,
-            fields_kind,
-            fields: parsed_fields,
-            value,
-        }
-    }
-}
-
-struct ParsedEnum {
-    options: HdlAttr<EnumOptions>,
-    vis: Visibility,
-    enum_token: Token![enum],
-    ident: Ident,
-    generics: Generics,
-    brace_token: Brace,
-    variants: Vec<ParsedVariant>,
-}
-
-impl ParsedEnum {
-    fn parse(item: ItemEnum) -> syn::Result<Self> {
-        let ItemEnum {
-            mut attrs,
-            vis,
-            enum_token,
-            ident,
-            generics,
-            brace_token,
-            variants,
-        } = item;
-        let mut errors = Errors::new();
-        let enum_options = errors
-            .unwrap_or_default(HdlAttr::parse_and_take_attr(&mut attrs))
-            .unwrap_or_default();
-        let variants = variants
-            .into_iter()
-            .map(|variant| {
-                ParsedVariant::parse(
-                    &mut errors,
-                    variant,
-                    &enum_options.body,
-                    &vis,
-                    &ident,
-                    &generics,
-                )
-            })
-            .collect();
-        errors.finish()?;
-        Ok(ParsedEnum {
-            options: enum_options,
-            vis,
-            enum_token,
-            ident,
-            generics,
-            brace_token,
-            variants,
-        })
-    }
-}
-
-impl ToTokens for ParsedEnum {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        let Self {
-            options,
-            vis,
-            enum_token,
-            ident: enum_ident,
-            generics: enum_generics,
-            brace_token,
-            variants,
-        } = self;
-        let EnumOptions {
-            outline_generated: _,
-            connect_inexact,
-            where_,
-            target,
-        } = &options.body;
-        let target = get_target(target, enum_ident);
-        let ValueDeriveGenerics {
-            generics: _,
-            static_type_generics,
-        } = ValueDeriveGenerics::get(enum_generics.clone(), where_);
-        let (static_type_impl_generics, static_type_type_generics, static_type_where_clause) =
-            static_type_generics.split_for_impl();
-        let type_struct_ident = format_ident!("__{}__Type", enum_ident);
-        let mut field_checks = vec![];
-        let mut make_type_struct_variant_type = |variant: &ParsedVariant| {
-            let VariantOptions {} = variant.options.body;
-            let (value_struct, parsed_struct) = match &variant.value {
-                VariantValue::None => {
-                    return None;
-                }
-                VariantValue::Direct { value_type } => {
-                    field_checks.push(quote_spanned! {value_type.span()=>
-                        __check_field::<#value_type>();
-                    });
-                    return Some(parse_quote! { <#value_type as ::fayalite::expr::ToExpr>::Type });
-                }
-                VariantValue::Struct {
-                    value_struct,
-                    parsed_struct,
-                } => (value_struct, parsed_struct),
-            };
-            value_struct.to_tokens(tokens);
-            parsed_struct.to_tokens(tokens);
-            let mut field_names = Vec::from_iter(get_field_names(&value_struct.fields));
-            derive_clone_hash_eq_partialeq_for_struct(
-                &value_struct.ident,
-                &static_type_generics,
-                &field_names,
-            )
-            .to_tokens(tokens);
-            field_names = Vec::from_iter(
-                field_names
-                    .into_iter()
-                    .zip(parsed_struct.fields.iter())
-                    .filter_map(|(member, field)| {
-                        field.options.body.skip.is_none().then_some(member)
-                    }),
-            );
-            let field_name_strs =
-                Vec::from_iter(field_names.iter().map(|v| v.to_token_stream().to_string()));
-            let debug_ident = format!("{enum_ident}::{}", variant.ident);
-            let debug_body = match variant.fields_kind {
-                FieldsKind::Unit => quote! {
-                    f.debug_struct(#debug_ident).finish()
-                },
-                FieldsKind::Named(_) => quote! {
-                    f.debug_struct(#debug_ident)
-                        #(.field(#field_name_strs, &self.#field_names))*
-                        .finish()
-                },
-                FieldsKind::Unnamed(_) => quote! {
-                    f.debug_tuple(#debug_ident)#(.field(&self.#field_names))*.finish()
-                },
-            };
-            let value_struct_ident = &value_struct.ident;
-            quote! {
-                #[automatically_derived]
-                impl #static_type_impl_generics ::fayalite::__std::fmt::Debug
-                    for #value_struct_ident #static_type_type_generics
-                #static_type_where_clause
-                {
-                    fn fmt(
-                        &self,
-                        f: &mut ::fayalite::__std::fmt::Formatter<'_>,
-                    ) -> ::fayalite::__std::fmt::Result {
-                        #debug_body
-                    }
-                }
-            }
-            .to_tokens(tokens);
-            Some(parse_quote! {
-                <
-                    #value_struct_ident #static_type_type_generics
-                    as ::fayalite::expr::ToExpr
-                >::Type
-            })
-        };
-        let type_struct_variants = Punctuated::from_iter(variants.iter().filter_map(|variant| {
-            let VariantOptions {} = variant.options.body;
-            Some(Field {
-                attrs: vec![],
-                vis: vis.clone(),
-                mutability: FieldMutability::None,
-                ident: Some(variant.ident.clone()),
-                colon_token: None, // it will fill in the colon if needed
-                ty: make_type_struct_variant_type(variant)?,
-            })
-        }));
-        let type_struct = ItemStruct {
-            attrs: vec![
-                parse_quote! {#[allow(non_camel_case_types)]},
-                parse_quote! {#[allow(non_snake_case)]},
-            ],
-            vis: vis.clone(),
-            struct_token: Token![struct](enum_token.span),
-            ident: type_struct_ident,
-            generics: static_type_generics.clone(),
-            fields: Fields::Named(FieldsNamed {
-                brace_token: *brace_token,
-                named: type_struct_variants,
-            }),
-            semi_token: None,
-        };
-        let type_struct_ident = &type_struct.ident;
-        let type_struct_debug_ident = format!("{enum_ident}::Type");
-        type_struct.to_tokens(tokens);
-        let non_empty_variant_names = Vec::from_iter(
-            variants
-                .iter()
-                .filter(|v| !v.value.is_none())
-                .map(|v| v.ident.clone()),
-        );
-        let non_empty_variant_name_strs =
-            Vec::from_iter(non_empty_variant_names.iter().map(|v| v.to_string()));
-        let debug_type_body = quote! {
-            f.debug_struct(#type_struct_debug_ident)
-                #(.field(#non_empty_variant_name_strs, &self.#non_empty_variant_names))*
-                .finish()
-        };
-        derive_clone_hash_eq_partialeq_for_struct(
-            type_struct_ident,
-            &static_type_generics,
-            &non_empty_variant_names,
-        )
-        .to_tokens(tokens);
-        let variant_names = Vec::from_iter(variants.iter().map(|v| &v.ident));
-        let variant_name_strs = Vec::from_iter(variant_names.iter().map(|v| v.to_string()));
-        let (variant_field_pats, variant_to_canonical_values): (Vec<_>, Vec<_>) = variants
-            .iter()
-            .map(|v| {
-                let field_names: Vec<_> = v.fields.iter().map(|field| &field.name).collect();
-                let var_names: Vec<_> = v.fields.iter().map(|field| field.var_name()).collect();
-                let field_pats = quote! {
-                    #(#field_names: #var_names,)*
-                };
-                let to_canonical_value = match &v.value {
-                    VariantValue::None => quote! { ::fayalite::__std::option::Option::None },
-                    VariantValue::Direct { .. } => {
-                        debug_assert_eq!(var_names.len(), 1);
-                        quote! {
-                            ::fayalite::__std::option::Option::Some(
-                                ::fayalite::ty::DynValueTrait::to_canonical_dyn(#(#var_names)*),
-                            )
-                        }
-                    }
-                    VariantValue::Struct {
-                        value_struct,
-                        parsed_struct,
-                    } => {
-                        let value_struct_ident = &value_struct.ident;
-                        let phantom_field_name = &parsed_struct
-                            .fields
-                            .last()
-                            .expect("missing phantom field")
-                            .name;
-                        let type_generics = static_type_type_generics.as_turbofish();
-                        quote! {
-                            ::fayalite::__std::option::Option::Some(
-                                ::fayalite::ty::DynValueTrait::to_canonical_dyn(
-                                    &#value_struct_ident #type_generics {
-                                        #(#field_names:
-                                            ::fayalite::__std::clone::Clone::clone(#var_names),)*
-                                        #phantom_field_name: ::fayalite::__std::marker::PhantomData,
-                                    },
-                                ),
-                            )
-                        }
-                    }
-                };
-                (field_pats, to_canonical_value)
-            })
-            .unzip();
-        let mut match_enum_variants = Punctuated::new();
-        let mut match_enum_debug_arms = vec![];
-        let mut match_enum_arms = vec![];
-        let mut variant_vars = vec![];
-        let mut from_canonical_type_variant_lets = vec![];
-        let mut non_empty_variant_vars = vec![];
-        let mut enum_type_variants = vec![];
-        let mut enum_type_variants_hint = vec![];
-        let match_enum_ident = format_ident!("__{}__MatchEnum", enum_ident);
-        let mut builder = Builder::new(format_ident!("__{}__Builder", enum_ident), vis.clone());
-        for variant in variants.iter() {
-            for field in variant.fields.iter() {
-                builder.insert_field(
-                    field.name.clone(),
-                    |v| {
-                        parse_quote_spanned! {v.span()=>
-                            ::fayalite::expr::ToExpr::to_expr(&#v)
-                        }
-                    },
-                    |t| {
-                        parse_quote_spanned! {t.span()=>
-                            ::fayalite::expr::Expr<<
-                                <#t as ::fayalite::expr::ToExpr>::Type
-                                as ::fayalite::ty::Type
-                            >::Value>
-                        }
-                    },
-                    |t| {
-                        parse_quote_spanned! {t.span()=>
-                            where
-                                #t: ::fayalite::expr::ToExpr,
-                        }
-                    },
-                );
-            }
-        }
-        let builder = builder.finish_filling_in_fields();
-        builder.to_tokens(tokens);
-        for (variant_index, variant) in variants.iter().enumerate() {
-            let variant_var = format_ident!("__v_{}", variant.ident);
-            let variant_name = &variant.ident;
-            let variant_name_str = variant.ident.to_string();
-            match_enum_variants.push(Variant {
-                attrs: vec![],
-                ident: variant.ident.clone(),
-                fields: variant.fields_kind.into_fields(variant.fields.iter().map(
-                    |ParsedField {
-                         options,
-                         vis,
-                         name,
-                         ty,
-                     }| {
-                        let FieldOptions {} = options.body;
-                        Field {
-                            attrs: vec![],
-                            vis: vis.clone(),
-                            mutability: FieldMutability::None,
-                            ident: if let Member::Named(name) = name {
-                                Some(name.clone())
-                            } else {
-                                None
-                            },
-                            colon_token: None,
-                            ty: parse_quote! { ::fayalite::expr::Expr<#ty> },
-                        }
-                    },
-                )),
-                discriminant: None,
-            });
-            let match_enum_field_names = Vec::from_iter(variant.fields.iter().map(
-                |ParsedField {
-                     options,
-                     vis: _,
-                     name,
-                     ty: _,
-                 }| {
-                    let FieldOptions {} = options.body;
-                    name
-                },
-            ));
-            let match_enum_field_name_strs = Vec::from_iter(variant.fields.iter().map(
-                |ParsedField {
-                     options,
-                     vis: _,
-                     name,
-                     ty: _,
-                 }| {
-                    let FieldOptions {} = options.body;
-                    name.to_token_stream().to_string()
-                },
-            ));
-            let match_enum_debug_vars = Vec::from_iter(variant.fields.iter().map(
-                |ParsedField {
-                     options,
-                     vis: _,
-                     name,
-                     ty: _,
-                 }| {
-                    let FieldOptions {} = options.body;
-                    format_ident!("__v_{}", name)
-                },
-            ));
-            match_enum_debug_arms.push(match variant.fields_kind {
-                FieldsKind::Unit | FieldsKind::Named(_) => quote! {
-                    Self::#variant_name {
-                        #(#match_enum_field_names: ref #match_enum_debug_vars,)*
-                    } => f.debug_struct(#variant_name_str)
-                        #(.field(#match_enum_field_name_strs, #match_enum_debug_vars))*
-                        .finish(),
-                },
-                FieldsKind::Unnamed(_) => quote! {
-                    Self::#variant_name(
-                        #(ref #match_enum_debug_vars,)*
-                    ) => f.debug_tuple(#variant_name_str)
-                        #(.field(#match_enum_debug_vars))*
-                        .finish(),
-                },
-            });
-            if let Some(value_ty) = variant.value.value_ty() {
-                from_canonical_type_variant_lets.push(quote! {
-                    let #variant_var =
-                        #variant_var.from_canonical_type_helper_has_value(#variant_name_str);
-                });
-                non_empty_variant_vars.push(variant_var.clone());
-                enum_type_variants.push(quote! {
-                    ::fayalite::enum_::VariantType {
-                        name: ::fayalite::intern::Intern::intern(#variant_name_str),
-                        ty: ::fayalite::__std::option::Option::Some(
-                            ::fayalite::ty::DynType::canonical_dyn(&self.#variant_name),
-                        ),
-                    }
-                });
-                enum_type_variants_hint.push(quote! {
-                    ::fayalite::enum_::VariantType {
-                        name: ::fayalite::intern::Intern::intern(#variant_name_str),
-                        ty: ::fayalite::__std::option::Option::Some(
-                            ::fayalite::bundle::TypeHint::<
-                                <#value_ty as ::fayalite::expr::ToExpr>::Type,
-                            >::intern_dyn(),
-                        ),
-                    }
-                });
-            } else {
-                from_canonical_type_variant_lets.push(quote! {
-                    #variant_var.from_canonical_type_helper_no_value(#variant_name_str);
-                });
-                enum_type_variants.push(quote! {
-                    ::fayalite::enum_::VariantType {
-                        name: ::fayalite::intern::Intern::intern(#variant_name_str),
-                        ty: ::fayalite::__std::option::Option::None,
-                    }
-                });
-                enum_type_variants_hint.push(quote! {
-                    ::fayalite::enum_::VariantType {
-                        name: ::fayalite::intern::Intern::intern(#variant_name_str),
-                        ty: ::fayalite::__std::option::Option::None,
-                    }
-                });
-            }
-            variant_vars.push(variant_var);
-            match_enum_arms.push(match &variant.value {
-                VariantValue::None => quote! {
-                    #variant_index => #match_enum_ident::#variant_name,
-                },
-                VariantValue::Direct { value_type } => quote! {
-                    #variant_index => #match_enum_ident::#variant_name {
-                        #(#match_enum_field_names)*: ::fayalite::expr::ToExpr::to_expr(
-                            &__variant_access.downcast_unchecked::<
-                                <#value_type as ::fayalite::expr::ToExpr>::Type>(),
-                        ),
-                    },
-                },
-                VariantValue::Struct {
-                    value_struct: ItemStruct { ident, .. },
-                    ..
-                } => quote! {
-                    #variant_index => {
-                        let __variant_access = ::fayalite::expr::ToExpr::to_expr(
-                            &__variant_access.downcast_unchecked::<<
-                                #ident #static_type_type_generics
-                                as ::fayalite::expr::ToExpr
-                            >::Type>(),
-                        );
-                        #match_enum_ident::#variant_name {
-                            #(#match_enum_field_names:
-                                (*__variant_access).#match_enum_field_names,)*
-                        }
-                    },
-                },
-            });
-            let builder_field_and_types = Vec::from_iter(variant.fields.iter().map(
-                |ParsedField {
-                     options,
-                     vis: _,
-                     name,
-                     ty,
-                 }| {
-                    let FieldOptions {} = options.body;
-                    (name, ty)
-                },
-            ));
-            let builder_field_vars = Vec::from_iter(
-                builder_field_and_types
-                    .iter()
-                    .map(|(name, _)| &builder.get_field(name).unwrap().1.builder_field_name),
-            );
-            let build_body = match &variant.value {
-                VariantValue::None => parse_quote! {
-                    {
-                        ::fayalite::expr::ToExpr::to_expr(
-                            &::fayalite::expr::ops::EnumLiteral::<
-                                #type_struct_ident #static_type_type_generics
-                            >::new_unchecked(
-                                ::fayalite::__std::option::Option::None,
-                                #variant_index,
-                                ::fayalite::ty::StaticType::static_type(),
-                            ),
-                        )
-                    }
-                },
-                VariantValue::Direct { value_type: _ } => parse_quote! {
-                    {
-                        ::fayalite::expr::ToExpr::to_expr(
-                            &::fayalite::expr::ops::EnumLiteral::<
-                                #type_struct_ident #static_type_type_generics
-                            >::new_unchecked(
-                                ::fayalite::__std::option::Option::Some(
-                                    #(#builder_field_vars)*.to_canonical_dyn(),
-                                ),
-                                #variant_index,
-                                ::fayalite::ty::StaticType::static_type(),
-                            ),
-                        )
-                    }
-                },
-                VariantValue::Struct {
-                    parsed_struct:
-                        ParsedStruct {
-                            names:
-                                ParsedStructNames {
-                                    type_struct_ident: field_type_struct_ident,
-                                    ..
-                                },
-                            ..
-                        },
-                    ..
-                } => parse_quote! {
-                    {
-                        let __builder = <
-                            #field_type_struct_ident #static_type_type_generics
-                            as ::fayalite::bundle::BundleType
-                        >::builder();
-                        #(let __builder = __builder.#builder_field_vars(#builder_field_vars);)*
-                        ::fayalite::expr::ToExpr::to_expr(
-                            &::fayalite::expr::ops::EnumLiteral::<
-                                #type_struct_ident #static_type_type_generics
-                            >::new_unchecked(
-                                ::fayalite::__std::option::Option::Some(
-                                    __builder.build().to_canonical_dyn(),
-                                ),
-                                #variant_index,
-                                ::fayalite::ty::StaticType::static_type(),
-                            ),
-                        )
-                    }
-                },
-            };
-            builder
-                .make_build_method(
-                    &format_ident!("variant_{}", variant_name),
-                    variant.fields.iter().map(
-                        |ParsedField {
-                             options,
-                             vis: _,
-                             name,
-                             ty,
-                         }| {
-                            let FieldOptions {} = options.body;
-                            (name.clone(), parse_quote! { ::fayalite::expr::Expr<#ty> })
-                        },
-                    ),
-                    &static_type_generics,
-                    &parse_quote! {#type_struct_ident #static_type_type_generics},
-                    &parse_quote! { ::fayalite::expr::Expr<#target #static_type_type_generics> },
-                    build_body,
-                )
-                .to_tokens(tokens);
-        }
-        let match_enum = ItemEnum {
-            attrs: vec![parse_quote! {#[allow(non_camel_case_types)]}],
-            vis: vis.clone(),
-            enum_token: *enum_token,
-            ident: match_enum_ident,
-            generics: static_type_generics.clone(),
-            brace_token: *brace_token,
-            variants: match_enum_variants,
-        };
-        let match_enum_ident = &match_enum.ident;
-        match_enum.to_tokens(tokens);
-        make_connect_impl(
-            *connect_inexact,
-            &static_type_generics,
-            type_struct_ident,
-            variants.iter().flat_map(|variant| {
-                variant.fields.iter().map(|field| {
-                    let ty = &field.ty;
-                    parse_quote_spanned! {field.name.span()=>
-                        <#ty as ::fayalite::expr::ToExpr>::Type
-                    }
-                })
-            }),
-        )
-        .to_tokens(tokens);
-        let variant_count = variants.len();
-        let empty_builder_ty = builder.ty([], Some(&parse_quote! { Self }), false);
-        quote! {
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::__std::fmt::Debug
-                for #match_enum_ident #static_type_type_generics
-            #static_type_where_clause
-            {
-                fn fmt(
-                    &self,
-                    f: &mut ::fayalite::__std::fmt::Formatter<'_>,
-                ) -> ::fayalite::__std::fmt::Result {
-                    match *self {
-                        #(#match_enum_debug_arms)*
-                    }
-                }
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::ty::StaticType
-                for #type_struct_ident #static_type_type_generics
-            #static_type_where_clause
-            {
-                fn static_type() -> Self {
-                    Self {
-                        #(#non_empty_variant_names: ::fayalite::ty::StaticType::static_type(),)*
-                    }
-                }
-            }
-
-            fn __check_field<T: ::fayalite::ty::Value>()
-            where
-                <T as ::fayalite::expr::ToExpr>::Type: ::fayalite::ty::Type<Value = T>,
-            {}
-            fn __check_fields #static_type_impl_generics(_: #target #static_type_type_generics)
-            #static_type_where_clause
-            {
-                #(#field_checks)*
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::__std::fmt::Debug
-                for #type_struct_ident #static_type_type_generics
-            #static_type_where_clause
-            {
-                fn fmt(
-                    &self,
-                    f: &mut ::fayalite::__std::fmt::Formatter<'_>,
-                ) -> ::fayalite::__std::fmt::Result {
-                    #debug_type_body
-                }
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::ty::Connect<::fayalite::type_deduction::UndeducedType>
-                for #type_struct_ident #static_type_type_generics
-            #static_type_where_clause
-            {}
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::ty::Type
-                for #type_struct_ident #static_type_type_generics
-            #static_type_where_clause
-            {
-                type CanonicalType = ::fayalite::enum_::DynEnumType;
-                type Value = #target #static_type_type_generics;
-                type CanonicalValue = ::fayalite::enum_::DynEnum;
-                type MaskType = ::fayalite::int::UIntType<1>;
-                type MaskValue = ::fayalite::int::UInt<1>;
-                type MatchVariant = #match_enum_ident #static_type_type_generics;
-                type MatchActiveScope = ::fayalite::module::Scope;
-                type MatchVariantAndInactiveScope =
-                    ::fayalite::enum_::EnumMatchVariantAndInactiveScope<Self>;
-                type MatchVariantsIter = ::fayalite::enum_::EnumMatchVariantsIter<Self>;
-                fn match_variants<IO: ::fayalite::bundle::BundleValue>(
-                    this: ::fayalite::expr::Expr<<Self as ::fayalite::ty::Type>::Value>,
-                    module_builder: &mut ::fayalite::module::ModuleBuilder<
-                        IO,
-                        ::fayalite::module::NormalModule,
-                    >,
-                    source_location: ::fayalite::source_location::SourceLocation,
-                ) -> <Self as ::fayalite::ty::Type>::MatchVariantsIter
-                where
-                    <IO as ::fayalite::expr::ToExpr>::Type:
-                        ::fayalite::bundle::BundleType<Value = IO>,
-                {
-                    module_builder.enum_match_variants_helper(this, source_location)
-                }
-                fn mask_type(&self) -> <Self as ::fayalite::ty::Type>::MaskType {
-                    ::fayalite::int::UIntType::new()
-                }
-                fn canonical(&self) -> <Self as ::fayalite::ty::Type>::CanonicalType {
-                    let variants = ::fayalite::enum_::EnumType::variants(self);
-                    ::fayalite::enum_::DynEnumType::new(variants)
-                }
-                fn source_location(&self) -> ::fayalite::source_location::SourceLocation {
-                    ::fayalite::source_location::SourceLocation::caller()
-                }
-                fn type_enum(&self) -> ::fayalite::ty::TypeEnum {
-                    ::fayalite::ty::TypeEnum::EnumType(::fayalite::ty::Type::canonical(self))
-                }
-                #[allow(non_snake_case)]
-                fn from_canonical_type(t: <Self as ::fayalite::ty::Type>::CanonicalType) -> Self {
-                    let [#(#variant_vars),*] = *::fayalite::enum_::EnumType::variants(&t) else {
-                        ::fayalite::__std::panic!("wrong number of variants");
-                    };
-                    #(#from_canonical_type_variant_lets)*
-                    Self {
-                        #(#non_empty_variant_names: #non_empty_variant_vars,)*
-                    }
-                }
-            }
-
-            #[automatically_derived]
-            #[allow(clippy::init_numbered_fields)]
-            impl #static_type_impl_generics ::fayalite::enum_::EnumType
-                for #type_struct_ident #static_type_type_generics
-            #static_type_where_clause
-            {
-                type Builder = #empty_builder_ty;
-                fn match_activate_scope(
-                    v: <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
-                ) -> (
-                    <Self as ::fayalite::ty::Type>::MatchVariant,
-                    <Self as ::fayalite::ty::Type>::MatchActiveScope,
-                ) {
-                    let (__variant_access, __scope) = v.activate();
-                    (
-                        match ::fayalite::expr::ops::VariantAccess::variant_index(
-                            &*__variant_access,
-                        ) {
-                            #(#match_enum_arms)*
-                            #variant_count.. => ::fayalite::__std::panic!("invalid variant index"),
-                        },
-                        __scope,
-                    )
-                }
-                fn builder() -> <Self as ::fayalite::enum_::EnumType>::Builder {
-                    #empty_builder_ty::new()
-                }
-                fn variants(&self) -> ::fayalite::intern::Interned<[::fayalite::enum_::VariantType<
-                    ::fayalite::intern::Interned<dyn ::fayalite::ty::DynCanonicalType>,
-                >]> {
-                    ::fayalite::intern::Intern::intern(&[#(#enum_type_variants,)*][..])
-                }
-                fn variants_hint() -> ::fayalite::enum_::VariantsHint {
-                    ::fayalite::enum_::VariantsHint::new([#(#enum_type_variants_hint,)*], false)
-                }
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::expr::ToExpr
-                for #target #static_type_type_generics
-            #static_type_where_clause
-            {
-                type Type = #type_struct_ident #static_type_type_generics;
-                fn ty(&self) -> <Self as ::fayalite::expr::ToExpr>::Type {
-                    ::fayalite::ty::StaticType::static_type()
-                }
-                fn to_expr(&self) -> ::fayalite::expr::Expr<Self> {
-                    ::fayalite::expr::Expr::from_value(self)
-                }
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::ty::Value
-                for #target #static_type_type_generics
-            #static_type_where_clause
-            {
-                fn to_canonical(&self) -> <
-                        <Self as ::fayalite::expr::ToExpr>::Type
-                        as ::fayalite::ty::Type
-                    >::CanonicalValue
-                {
-                    let __ty = ::fayalite::ty::Type::canonical(&::fayalite::expr::ToExpr::ty(self));
-                    match self {
-                        #(Self::#variant_names { #variant_field_pats } => {
-                            ::fayalite::enum_::DynEnum::new_by_name(
-                                __ty,
-                                ::fayalite::intern::Intern::intern(#variant_name_strs),
-                                #variant_to_canonical_values,
-                            )
-                        })*
-                    }
-                }
-            }
-
-            #[automatically_derived]
-            impl #static_type_impl_generics ::fayalite::enum_::EnumValue
-                for #target #static_type_type_generics
-            #static_type_where_clause
-            {
-            }
-        }
-        .to_tokens(tokens);
-    }
-}
-
-pub(crate) fn value_derive_enum(item: ItemEnum) -> syn::Result<TokenStream> {
-    let item = ParsedEnum::parse(item)?;
-    let outline_generated = item.options.body.outline_generated;
-    let mut contents = quote! {
-        const _: () = {
-            #item
-        };
-    };
-    if outline_generated.is_some() {
-        contents = crate::outline_generated(contents, "value-enum-");
-    }
-    Ok(contents)
-}
--- a/crates/fayalite-proc-macros-impl/src/value_derive_struct.rs
+++ b/crates/fayalite-proc-macros-impl/src/value_derive_struct.rs
@ -1,771 +0,0 @@
-// SPDX-License-Identifier: LGPL-3.0-or-later
-// See Notices.txt for copyright information
-use crate::{
-    value_derive_common::{
-        append_field, derive_clone_hash_eq_partialeq_for_struct, get_target, make_connect_impl,
-        Bounds, Builder, FieldsKind, ParsedField, ValueDeriveGenerics,
-    },
-    Errors, HdlAttr,
-};
-use proc_macro2::TokenStream;
-use quote::{format_ident, quote, quote_spanned, ToTokens};
-use syn::{
-    parse_quote, parse_quote_spanned, spanned::Spanned, FieldMutability, Generics, Ident,
-    ItemStruct, Member, Path, Token, Visibility,
-};
-
-crate::options! {
-    #[options = StructOptions]
-    pub(crate) enum StructOption {
-        OutlineGenerated(outline_generated),
-        Static(static_),
-        ConnectInexact(connect_inexact),
-        Bounds(where_, Bounds),
-        Target(target, Path),
-    }
-}
-
-crate::options! {
-    #[options = FieldOptions]
-    pub(crate) enum FieldOption {
-        Flip(flip),
-        Skip(skip),
-    }
-}
-
-pub(crate) struct ParsedStructNames<I, S> {
-    pub(crate) ident: Ident,
-    pub(crate) type_struct_debug_ident: S,
-    pub(crate) type_struct_ident: Ident,
-    pub(crate) match_variant_ident: I,
-    pub(crate) builder_struct_ident: I,
-    pub(crate) mask_match_variant_ident: I,
-    pub(crate) mask_type_ident: I,
-    pub(crate) mask_type_debug_ident: S,
-    pub(crate) mask_value_ident: I,
-    pub(crate) mask_value_debug_ident: S,
-    pub(crate) mask_builder_struct_ident: I,
-}
-
-pub(crate) struct ParsedStruct {
-    pub(crate) options: HdlAttr<StructOptions>,
-    pub(crate) vis: Visibility,
-    pub(crate) struct_token: Token![struct],
-    pub(crate) generics: Generics,
-    pub(crate) fields_kind: FieldsKind,
-    pub(crate) fields: Vec<ParsedField<FieldOptions>>,
-    pub(crate) semi_token: Option<Token![;]>,
-    pub(crate) skip_check_fields: bool,
-    pub(crate) names: ParsedStructNames<Option<Ident>, Option<String>>,
-}
-
-impl ParsedStruct {
-    pub(crate) fn parse(item: &mut ItemStruct) -> syn::Result<Self> {
-        let ItemStruct {
-            attrs,
-            vis,
-            struct_token,
-            ident,
-            generics,
-            fields,
-            semi_token,
-        } = item;
-        let mut errors = Errors::new();
-        let struct_options = errors
-            .unwrap_or_default(HdlAttr::parse_and_take_attr(attrs))
-            .unwrap_or_default();
-        let (fields_kind, fields) = ParsedField::parse_fields(&mut errors, fields, false);
-        errors.finish()?;
-        Ok(ParsedStruct {
-            options: struct_options,
-            vis: vis.clone(),
-            struct_token: *struct_token,
-            generics: generics.clone(),
-            fields_kind,
-            fields,
-            semi_token: *semi_token,
-            skip_check_fields: false,
-            names: ParsedStructNames {
-                ident: ident.clone(),
-                type_struct_debug_ident: None,
-                type_struct_ident: format_ident!("__{}__Type", ident),
-                match_variant_ident: None,
-                builder_struct_ident: None,
-                mask_match_variant_ident: None,
-                mask_type_ident: None,
-                mask_type_debug_ident: None,
-                mask_value_ident: None,
-                mask_value_debug_ident: None,
-                mask_builder_struct_ident: None,
-            },
-        })
-    }
-    pub(crate) fn write_body(
-        &self,
-        target: Path,
-        names: ParsedStructNames<&Ident, &String>,
-        is_for_mask: bool,
-        tokens: &mut TokenStream,
-    ) {
-        let Self {
-            options,
-            vis,
-            struct_token,
-            generics,
-            fields_kind,
-            fields,
-            semi_token,
-            skip_check_fields,
-            names: _,
-        } = self;
-        let skip_check_fields = *skip_check_fields || is_for_mask;
-        let ParsedStructNames {
-            ident: struct_ident,
-            type_struct_debug_ident,
-            type_struct_ident,
-            match_variant_ident,
-            builder_struct_ident,
-            mask_match_variant_ident: _,
-            mask_type_ident,
-            mask_type_debug_ident: _,
-            mask_value_ident,
-            mask_value_debug_ident,
-            mask_builder_struct_ident: _,
-        } = names;
-        let StructOptions {
-            outline_generated: _,
-            where_,
-            target: _,
-            static_,
-            connect_inexact,
-        } = &options.body;
-        let ValueDeriveGenerics {
-            generics,
-            static_type_generics,
-        } = ValueDeriveGenerics::get(generics.clone(), where_);
-        let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
-        let unskipped_fields = fields
-            .iter()
-            .filter(|field| field.options.body.skip.is_none());
-        let _field_names = Vec::from_iter(fields.iter().map(|field| field.name.clone()));
-        let unskipped_field_names =
-            Vec::from_iter(unskipped_fields.clone().map(|field| field.name.clone()));
-        let unskipped_field_name_strs = Vec::from_iter(
-            unskipped_field_names
-                .iter()
-                .map(|field_name| field_name.to_token_stream().to_string()),
-        );
-        let unskipped_field_vars = Vec::from_iter(
-            unskipped_field_names
-                .iter()
-                .map(|field_name| format_ident!("__v_{}", field_name)),
-        );
-        let unskipped_field_flips = Vec::from_iter(
-            unskipped_fields
-                .clone()
-                .map(|field| field.options.body.flip.is_some()),
-        );
-        let mut any_fields_skipped = false;
-        let type_fields = Vec::from_iter(fields.iter().filter_map(|field| {
-            let ParsedField {
-                options,
-                vis,
-                name,
-                ty,
-            } = field;
-            let FieldOptions { flip: _, skip } = &options.body;
-            if skip.is_some() {
-                any_fields_skipped = true;
-                return None;
-            }
-            let ty = if is_for_mask {
-                parse_quote! { ::fayalite::ty::AsMask<#ty> }
-            } else {
-                ty.to_token_stream()
-            };
-            Some(syn::Field {
-                attrs: vec![],
-                vis: vis.clone(),
-                mutability: FieldMutability::None,
-                ident: match name.clone() {
-                    Member::Named(name) => Some(name),
-                    Member::Unnamed(_) => None,
-                },
-                colon_token: None,
-                ty: parse_quote! { <#ty as ::fayalite::expr::ToExpr>::Type },
-            })
-        }));
-        let field_types = Vec::from_iter(type_fields.iter().map(|field| field.ty.clone()));
-        let match_variant_fields = Vec::from_iter(fields.iter().zip(&type_fields).map(
-            |(parsed_field, type_field)| {
-                let field_ty = &parsed_field.ty;
-                syn::Field {
-                    ty: parse_quote! { ::fayalite::expr::Expr<#field_ty> },
-                    ..type_field.clone()
-                }
-            },
-        ));
-
-        let mask_value_fields = Vec::from_iter(fields.iter().zip(&type_fields).map(
-            |(parsed_field, type_field)| {
-                let field_ty = &parsed_field.ty;
-                syn::Field {
-                    ty: parse_quote! { ::fayalite::ty::AsMask<#field_ty> },
-                    ..type_field.clone()
-                }
-            },
-        ));
-
-        let mut type_struct_fields = fields_kind.into_fields(type_fields);
-        let mut match_variant_fields = fields_kind.into_fields(match_variant_fields);
-        let mut mask_value_fields = fields_kind.into_fields(mask_value_fields);
-        let phantom_data_field_name = any_fields_skipped.then(|| {
-            let phantom_data_field_name = Ident::new("__phantom_data", type_struct_ident.span());
-            let member = append_field(
-                &mut type_struct_fields,
-                syn::Field {
-                    attrs: vec![],
-                    vis: vis.clone(),
-                    mutability: FieldMutability::None,
-                    ident: Some(phantom_data_field_name.clone()),
-                    colon_token: None,
-                    ty: parse_quote_spanned! {type_struct_ident.span()=>
-                        ::fayalite::__std::marker::PhantomData<#struct_ident #type_generics>
-                    },
-                },
-            );
-            append_field(
-                &mut match_variant_fields,
-                syn::Field {
-                    attrs: vec![],
-                    vis: Visibility::Inherited,
-                    mutability: FieldMutability::None,
-                    ident: Some(phantom_data_field_name.clone()),
-                    colon_token: None,
-                    ty: parse_quote_spanned! {type_struct_ident.span()=>
-                        ::fayalite::__std::marker::PhantomData<#struct_ident #type_generics>
-                    },
-                },
-            );
-            append_field(
-                &mut mask_value_fields,
-                syn::Field {
-                    attrs: vec![],
-                    vis: Visibility::Inherited,
-                    mutability: FieldMutability::None,
-                    ident: Some(phantom_data_field_name),
-                    colon_token: None,
-                    ty: parse_quote_spanned! {type_struct_ident.span()=>
-                        ::fayalite::__std::marker::PhantomData<#struct_ident #type_generics>
-                    },
-                },
-            );
-            member
-        });
-        let phantom_data_field_name_slice = phantom_data_field_name.as_slice();
-        let type_struct = ItemStruct {
-            attrs: vec![parse_quote! {#[allow(non_camel_case_types)]}],
-            vis: vis.clone(),
-            struct_token: *struct_token,
-            ident: type_struct_ident.clone(),
-            generics: generics.clone(),
-            fields: type_struct_fields,
-            semi_token: *semi_token,
-        };
-        type_struct.to_tokens(tokens);
-        let match_variant_struct = ItemStruct {
-            attrs: vec![parse_quote! {#[allow(non_camel_case_types)]}],
-            vis: vis.clone(),
-            struct_token: *struct_token,
-            ident: match_variant_ident.clone(),
-            generics: generics.clone(),
-            fields: match_variant_fields,
-            semi_token: *semi_token,
-        };
-        match_variant_struct.to_tokens(tokens);
-        let mask_type_body = if is_for_mask {
-            quote! {
-                ::fayalite::__std::clone::Clone::clone(self)
-            }
-        } else {
-            let mask_value_struct = ItemStruct {
-                attrs: vec![parse_quote! {#[allow(non_camel_case_types)]}],
-                vis: vis.clone(),
-                struct_token: *struct_token,
-                ident: mask_value_ident.clone(),
-                generics: generics.clone(),
-                fields: mask_value_fields,
-                semi_token: *semi_token,
-            };
-            mask_value_struct.to_tokens(tokens);
-            let debug_mask_value_body = match fields_kind {
-                FieldsKind::Unit => quote! {
-                    f.debug_struct(#mask_value_debug_ident).finish()
-                },
-                FieldsKind::Named(_) => quote! {
-                    f.debug_struct(#mask_value_debug_ident)
-                        #(.field(#unskipped_field_name_strs, &self.#unskipped_field_names))*
-                        .finish()
-                },
-                FieldsKind::Unnamed(_) => quote! {
-                    f.debug_tuple(#mask_value_debug_ident)
-                        #(.field(&self.#unskipped_field_names))*
-                        .finish()
-                },
-            };
-            quote! {
-                #[automatically_derived]
-                impl #impl_generics ::fayalite::__std::fmt::Debug
-                    for #mask_value_ident #type_generics
-                #where_clause
-                {
-                    fn fmt(
-                        &self,
-                        f: &mut ::fayalite::__std::fmt::Formatter<'_>,
-                    ) -> ::fayalite::__std::fmt::Result {
-                        #debug_mask_value_body
-                    }
-                }
-            }
-            .to_tokens(tokens);
-            quote! {
-                #mask_type_ident {
-                    #(#unskipped_field_names:
-                        ::fayalite::ty::Type::mask_type(&self.#unskipped_field_names),)*
-                    #(#phantom_data_field_name_slice: ::fayalite::__std::marker::PhantomData,)*
-                }
-            }
-        };
-        let debug_type_body = match fields_kind {
-            FieldsKind::Unit => quote! {
-                f.debug_struct(#type_struct_debug_ident).finish()
-            },
-            FieldsKind::Named(_) => quote! {
-                f.debug_struct(#type_struct_debug_ident)
-                    #(.field(#unskipped_field_name_strs, &self.#unskipped_field_names))*
-                    .finish()
-            },
-            FieldsKind::Unnamed(_) => quote! {
-                f.debug_tuple(#type_struct_debug_ident)
-                    #(.field(&self.#unskipped_field_names))*
-                    .finish()
-            },
-        };
-        for the_struct_ident in [&type_struct_ident, match_variant_ident]
-            .into_iter()
-            .chain(is_for_mask.then_some(mask_value_ident))
-        {
-            derive_clone_hash_eq_partialeq_for_struct(
-                the_struct_ident,
-                &generics,
-                &Vec::from_iter(
-                    unskipped_field_names
-                        .iter()
-                        .cloned()
-                        .chain(phantom_data_field_name.clone()),
-                ),
-            )
-            .to_tokens(tokens);
-        }
-        let check_v = format_ident!("__v");
-        let field_checks = Vec::from_iter(fields.iter().map(|ParsedField { ty, name, .. }| {
-            quote_spanned! {ty.span()=>
-                __check_field(#check_v.#name);
-            }
-        }));
-        if static_.is_some() {
-            let (impl_generics, type_generics, where_clause) =
-                static_type_generics.split_for_impl();
-            quote! {
-                #[automatically_derived]
-                impl #impl_generics ::fayalite::ty::StaticType for #type_struct_ident #type_generics
-                #where_clause
-                {
-                    fn static_type() -> Self {
-                        Self {
-                            #(#unskipped_field_names: ::fayalite::ty::StaticType::static_type(),)*
-                            #(#phantom_data_field_name_slice:
-                                ::fayalite::__std::marker::PhantomData,)*
-                        }
-                    }
-                }
-            }
-            .to_tokens(tokens);
-        }
-        if !skip_check_fields {
-            quote! {
-                fn __check_field<T: ::fayalite::ty::Value>(_v: T)
-                where
-                    <T as ::fayalite::expr::ToExpr>::Type: ::fayalite::ty::Type<Value = T>,
-                {}
-                fn __check_fields #impl_generics(#check_v: #target #type_generics)
-                #where_clause
-                {
-                    #(#field_checks)*
-                }
-            }
-            .to_tokens(tokens);
-        }
-        let mut builder = Builder::new(builder_struct_ident.clone(), vis.clone());
-        for field in unskipped_fields.clone() {
-            builder.insert_field(
-                field.name.clone(),
-                |v| {
-                    parse_quote_spanned! {v.span()=>
-                        ::fayalite::expr::ToExpr::to_expr(&#v)
-                    }
-                },
-                |t| {
-                    parse_quote_spanned! {t.span()=>
-                        ::fayalite::expr::Expr<<
-                            <#t as ::fayalite::expr::ToExpr>::Type
-                            as ::fayalite::ty::Type
-                        >::Value>
-                    }
-                },
-                |t| {
-                    parse_quote_spanned! {t.span()=>
-                        where
-                            #t: ::fayalite::expr::ToExpr,
-                    }
-                },
-            );
-        }
-        let builder = builder.finish_filling_in_fields();
-        builder.to_tokens(tokens);
-        let build_type_fields =
-            Vec::from_iter(unskipped_fields.clone().map(|ParsedField { name, .. }| {
-                let builder_field_name = &builder.get_field(name).unwrap().1.builder_field_name;
-                quote_spanned! {struct_ident.span()=>
-                    #name: ::fayalite::expr::ToExpr::ty(&#builder_field_name)
-                }
-            }));
-        let build_expr_fields =
-            Vec::from_iter(unskipped_fields.clone().map(|ParsedField { name, .. }| {
-                let builder_field_name = &builder.get_field(name).unwrap().1.builder_field_name;
-                quote_spanned! {struct_ident.span()=>
-                    #builder_field_name.to_canonical_dyn()
-                }
-            }));
-        let build_specified_fields = unskipped_fields.clone().map(
-            |ParsedField {
-                 options: _,
-                 vis: _,
-                 name,
-                 ty,
-             }| {
-                let ty = if is_for_mask {
-                    parse_quote_spanned! {name.span()=>
-                        ::fayalite::expr::Expr<::fayalite::ty::AsMask<#ty>>
-                    }
-                } else {
-                    parse_quote_spanned! {name.span()=>
-                        ::fayalite::expr::Expr<#ty>
-                    }
-                };
-                (name.clone(), ty)
-            },
-        );
-        let build_body = parse_quote_spanned! {struct_ident.span()=>
-            {
-                ::fayalite::expr::ToExpr::to_expr(
-                    &::fayalite::expr::ops::BundleLiteral::new_unchecked(
-                        ::fayalite::intern::Intern::intern(&[#(
-                            #build_expr_fields,
-                        )*][..]),
-                        #type_struct_ident {
-                            #(#build_type_fields,)*
-                            #(#phantom_data_field_name_slice:
-                                ::fayalite::__std::marker::PhantomData,)*
-                        },
-                    ),
-                )
-            }
-        };
-        builder
-            .make_build_method(
-                &Ident::new("build", struct_ident.span()),
-                build_specified_fields,
-                &generics,
-                &parse_quote_spanned! {struct_ident.span()=>
-                    #type_struct_ident #type_generics
-                },
-                &parse_quote_spanned! {struct_ident.span()=>
-                    ::fayalite::expr::Expr<#target #type_generics>
-                },
-                build_body,
-            )
-            .to_tokens(tokens);
-        make_connect_impl(
-            *connect_inexact,
-            &generics,
-            &type_struct_ident,
-            unskipped_fields.clone().map(|field| {
-                let ty = &field.ty;
-                parse_quote_spanned! {field.name.span()=>
-                    <#ty as ::fayalite::expr::ToExpr>::Type
-                }
-            }),
-        )
-        .to_tokens(tokens);
-        let empty_builder_ty = builder.ty([], Some(&parse_quote! { Self }), false);
-        quote! {
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::__std::fmt::Debug for #type_struct_ident #type_generics
-            #where_clause
-            {
-                fn fmt(
-                    &self,
-                    f: &mut ::fayalite::__std::fmt::Formatter<'_>,
-                ) -> ::fayalite::__std::fmt::Result {
-                    #debug_type_body
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::ty::Connect<::fayalite::type_deduction::UndeducedType>
-                for #type_struct_ident #type_generics
-            #where_clause
-            {}
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::ty::Type for #type_struct_ident #type_generics
-            #where_clause
-            {
-                type CanonicalType = ::fayalite::bundle::DynBundleType;
-                type Value = #target #type_generics;
-                type CanonicalValue = ::fayalite::bundle::DynBundle;
-                type MaskType = #mask_type_ident #type_generics;
-                type MaskValue = #mask_value_ident #type_generics;
-                type MatchVariant = #match_variant_ident #type_generics;
-                type MatchActiveScope = ();
-                type MatchVariantAndInactiveScope = ::fayalite::ty::MatchVariantWithoutScope<
-                    #match_variant_ident #type_generics,
-                >;
-                type MatchVariantsIter = ::fayalite::__std::iter::Once<
-                    <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
-                >;
-                #[allow(unused_variables)]
-                fn match_variants<IO: ::fayalite::bundle::BundleValue>(
-                    this: ::fayalite::expr::Expr<<Self as ::fayalite::ty::Type>::Value>,
-                    module_builder: &mut ::fayalite::module::ModuleBuilder<
-                        IO,
-                        ::fayalite::module::NormalModule,
-                    >,
-                    source_location: ::fayalite::source_location::SourceLocation,
-                ) -> <Self as ::fayalite::ty::Type>::MatchVariantsIter
-                where
-                    <IO as ::fayalite::expr::ToExpr>::Type:
-                        ::fayalite::bundle::BundleType<Value = IO>,
-                {
-                    ::fayalite::__std::iter::once(::fayalite::ty::MatchVariantWithoutScope(
-                        #match_variant_ident {
-                            #(#unskipped_field_names: this.field(#unskipped_field_name_strs),)*
-                            #(#phantom_data_field_name_slice:
-                                ::fayalite::__std::marker::PhantomData,)*
-                        },
-                    ))
-                }
-                fn mask_type(&self) -> <Self as ::fayalite::ty::Type>::MaskType {
-                    #mask_type_body
-                }
-                fn canonical(&self) -> <Self as ::fayalite::ty::Type>::CanonicalType {
-                    let fields = ::fayalite::bundle::BundleType::fields(self);
-                    ::fayalite::bundle::DynBundleType::new(fields)
-                }
-                fn source_location(&self) -> ::fayalite::source_location::SourceLocation {
-                    ::fayalite::source_location::SourceLocation::caller()
-                }
-                fn type_enum(&self) -> ::fayalite::ty::TypeEnum {
-                    ::fayalite::ty::TypeEnum::BundleType(::fayalite::ty::Type::canonical(self))
-                }
-                fn from_canonical_type(t: <Self as ::fayalite::ty::Type>::CanonicalType) -> Self {
-                    let [#(#unskipped_field_vars),*] = *::fayalite::bundle::BundleType::fields(&t)
-                    else {
-                        ::fayalite::__std::panic!("wrong number of fields");
-                    };
-                    Self {
-                        #(#unskipped_field_names: #unskipped_field_vars.from_canonical_type_helper(
-                            #unskipped_field_name_strs,
-                            #unskipped_field_flips,
-                        ),)*
-                        #(#phantom_data_field_name_slice: ::fayalite::__std::marker::PhantomData,)*
-                    }
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::ty::TypeWithDeref for #type_struct_ident #type_generics
-            #where_clause
-            {
-                #[allow(unused_variables)]
-                fn expr_deref(this: &::fayalite::expr::Expr<<Self as ::fayalite::ty::Type>::Value>)
-                    -> &<Self as ::fayalite::ty::Type>::MatchVariant
-                {
-                    ::fayalite::intern::Interned::<_>::into_inner(
-                        ::fayalite::intern::Intern::intern_sized(#match_variant_ident {
-                            #(#unskipped_field_names: this.field(#unskipped_field_name_strs),)*
-                            #(#phantom_data_field_name_slice:
-                                ::fayalite::__std::marker::PhantomData,)*
-                        }),
-                    )
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::bundle::BundleType for #type_struct_ident #type_generics
-            #where_clause
-            {
-                type Builder = #empty_builder_ty;
-                fn builder() -> <Self as ::fayalite::bundle::BundleType>::Builder {
-                    #empty_builder_ty::new()
-                }
-                fn fields(&self) -> ::fayalite::intern::Interned<
-                        [::fayalite::bundle::FieldType<::fayalite::intern::Interned<
-                            dyn ::fayalite::ty::DynCanonicalType,
-                        >>],
-                    >
-                {
-                    ::fayalite::intern::Intern::intern(&[#(
-                        ::fayalite::bundle::FieldType {
-                            name: ::fayalite::intern::Intern::intern(#unskipped_field_name_strs),
-                            flipped: #unskipped_field_flips,
-                            ty: ::fayalite::ty::DynType::canonical_dyn(
-                                &self.#unskipped_field_names,
-                            ),
-                        },
-                    )*][..])
-                }
-                fn fields_hint() -> ::fayalite::bundle::FieldsHint {
-                    ::fayalite::bundle::FieldsHint::new([#(
-                        ::fayalite::bundle::FieldType {
-                            name: ::fayalite::intern::Intern::intern(#unskipped_field_name_strs),
-                            flipped: #unskipped_field_flips,
-                            ty: ::fayalite::bundle::TypeHint::<#field_types>::intern_dyn(),
-                        },
-                    )*], false)
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::expr::ToExpr for #target #type_generics
-            #where_clause
-            {
-                type Type = #type_struct_ident #type_generics;
-                fn ty(&self) -> <Self as ::fayalite::expr::ToExpr>::Type {
-                    #type_struct_ident {
-                        #(#unskipped_field_names: ::fayalite::expr::ToExpr::ty(
-                            &self.#unskipped_field_names,
-                        ),)*
-                        #(#phantom_data_field_name_slice: ::fayalite::__std::marker::PhantomData,)*
-                    }
-                }
-                fn to_expr(&self) -> ::fayalite::expr::Expr<Self> {
-                    ::fayalite::expr::Expr::from_value(self)
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::ty::Value for #target #type_generics
-            #where_clause
-            {
-                fn to_canonical(&self) -> <
-                        <Self as ::fayalite::expr::ToExpr>::Type
-                        as ::fayalite::ty::Type
-                    >::CanonicalValue
-                {
-                    let ty = ::fayalite::ty::Type::canonical(&::fayalite::expr::ToExpr::ty(self));
-                    ::fayalite::bundle::DynBundle::new(ty, ::fayalite::__std::sync::Arc::new([
-                        #(::fayalite::ty::DynValueTrait::to_canonical_dyn(
-                            &self.#unskipped_field_names,
-                        ),)*
-                    ]))
-                }
-            }
-
-            #[automatically_derived]
-            impl #impl_generics ::fayalite::bundle::BundleValue for #target #type_generics
-            #where_clause
-            {
-            }
-        }
-        .to_tokens(tokens);
-    }
-}
-
-impl ToTokens for ParsedStruct {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        let ParsedStructNames {
-            ident: struct_ident,
-            type_struct_debug_ident,
-            type_struct_ident,
-            match_variant_ident,
-            builder_struct_ident,
-            mask_match_variant_ident,
-            mask_type_ident,
-            mask_type_debug_ident,
-            mask_value_ident,
-            mask_value_debug_ident,
-            mask_builder_struct_ident,
-        } = &self.names;
-        macro_rules! unwrap_or_set {
-            ($(let $var:ident =? $fallback_value:expr;)*) => {
-                $(let $var = $var.clone().unwrap_or_else(|| $fallback_value);)*
-            };
-        }
-        unwrap_or_set! {
-            let type_struct_debug_ident =? format!("{struct_ident}::Type");
-            let match_variant_ident =? format_ident!("__{}__MatchVariant", struct_ident);
-            let builder_struct_ident =? format_ident!("__{}__Builder", struct_ident);
-            let mask_match_variant_ident =? format_ident!("__AsMask__{}__MatchVariant", struct_ident);
-            let mask_type_ident =? format_ident!("__AsMask__{}__Type", struct_ident);
-            let mask_type_debug_ident =? format!("AsMask<{struct_ident}>::Type");
-            let mask_value_ident =? format_ident!("__AsMask__{}", struct_ident);
-            let mask_value_debug_ident =? format!("AsMask<{struct_ident}>");
-            let mask_builder_struct_ident =? format_ident!("__AsMask__{}__Builder", struct_ident);
-        }
-        let target = get_target(&self.options.body.target, struct_ident);
-        let names = ParsedStructNames {
-            ident: struct_ident.clone(),
-            type_struct_debug_ident: &type_struct_debug_ident,
-            type_struct_ident: type_struct_ident.clone(),
-            match_variant_ident: &match_variant_ident,
-            builder_struct_ident: &builder_struct_ident,
-            mask_match_variant_ident: &mask_match_variant_ident,
-            mask_type_ident: &mask_type_ident,
-            mask_type_debug_ident: &mask_type_debug_ident,
-            mask_value_ident: &mask_value_ident,
-            mask_value_debug_ident: &mask_value_debug_ident,
-            mask_builder_struct_ident: &mask_builder_struct_ident,
-        };
-        self.write_body(target, names, false, tokens);
-        let mask_names = ParsedStructNames {
-            ident: mask_value_ident.clone(),
-            type_struct_debug_ident: &mask_type_debug_ident,
-            type_struct_ident: mask_type_ident.clone(),
-            match_variant_ident: &mask_match_variant_ident,
-            builder_struct_ident: &mask_builder_struct_ident,
-            mask_match_variant_ident: &mask_match_variant_ident,
-            mask_type_ident: &mask_type_ident,
-            mask_type_debug_ident: &mask_type_debug_ident,
-            mask_value_ident: &mask_value_ident,
-            mask_value_debug_ident: &mask_value_debug_ident,
-            mask_builder_struct_ident: &mask_builder_struct_ident,
-        };
-        self.write_body(mask_value_ident.clone().into(), mask_names, true, tokens);
-    }
-}
-
-pub(crate) fn value_derive_struct(mut item: ItemStruct) -> syn::Result<TokenStream> {
-    let item = ParsedStruct::parse(&mut item)?;
-    let outline_generated = item.options.body.outline_generated;
-    let mut contents = quote! {
-        const _: () = {
-            #item
-        };
-    };
-    if outline_generated.is_some() {
-        contents = crate::outline_generated(contents, "value-struct-");
-    }
-    Ok(contents)
-}
--- a/crates/fayalite-proc-macros/Cargo.toml
+++ b/crates/fayalite-proc-macros/Cargo.toml
@ -16,4 +16,4 @@ version.workspace = true
 proc-macro = true

 [dependencies]
-fayalite-proc-macros-impl = { workspace = true }
+fayalite-proc-macros-impl.workspace = true
--- a/crates/fayalite-proc-macros/src/lib.rs
+++ b/crates/fayalite-proc-macros/src/lib.rs
@ -2,7 +2,7 @@
 // See Notices.txt for copyright information
 //! proc macros for `fayalite`
 //!
-//! see `fayalite::hdl_module` and `fayalite::ty::Value` for docs
+//! see `fayalite::hdl_module` and `fayalite::hdl` for docs

 // intentionally not documented here, see `fayalite::hdl_module` for docs
 #[proc_macro_attribute]
@ -10,16 +10,19 @@ pub fn hdl_module(
    attr: proc_macro::TokenStream,
    item: proc_macro::TokenStream,
 ) -> proc_macro::TokenStream {
-    match fayalite_proc_macros_impl::module(attr.into(), item.into()) {
+    match fayalite_proc_macros_impl::hdl_module(attr.into(), item.into()) {
        Ok(retval) => retval.into(),
        Err(err) => err.into_compile_error().into(),
    }
 }

-// intentionally not documented here, see `fayalite::ty::Value` for docs
-#[proc_macro_derive(Value, attributes(hdl))]
-pub fn value_derive(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    match fayalite_proc_macros_impl::value_derive(item.into()) {
+// intentionally not documented here, see `fayalite::hdl` for docs
+#[proc_macro_attribute]
+pub fn hdl(
+    attr: proc_macro::TokenStream,
+    item: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    match fayalite_proc_macros_impl::hdl_attr(attr.into(), item.into()) {
        Ok(retval) => retval.into(),
        Err(err) => err.into_compile_error().into(),
    }
--- a/crates/fayalite-visit-gen/Cargo.toml
+++ b/crates/fayalite-visit-gen/Cargo.toml
@ -13,11 +13,11 @@ rust-version.workspace = true
 version.workspace = true

 [dependencies]
-indexmap = { workspace = true }
-prettyplease = { workspace = true }
-proc-macro2 = { workspace = true }
-quote = { workspace = true }
-serde = { workspace = true }
-serde_json = { workspace = true }
-syn = { workspace = true }
-thiserror = { workspace = true }
+indexmap.workspace = true
+prettyplease.workspace = true
+proc-macro2.workspace = true
+quote.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+syn.workspace = true
+thiserror.workspace = true
--- a/crates/fayalite/Cargo.toml
+++ b/crates/fayalite/Cargo.toml
@ -14,25 +14,33 @@ rust-version.workspace = true
 version.workspace = true

 [dependencies]
-bitvec = { workspace = true }
-hashbrown = { workspace = true }
-num-bigint = { workspace = true }
-num-traits = { workspace = true }
-fayalite-proc-macros = { workspace = true }
-serde = { workspace = true }
-serde_json = { workspace = true }
-clap = { version = "4.5.9", features = ["derive", "env"] }
-eyre = "0.6.12"
-which = "6.0.1"
+bitvec.workspace = true
+blake3.workspace = true
+clap.workspace = true
+ctor.workspace = true
+eyre.workspace = true
+fayalite-proc-macros.workspace = true
+hashbrown.workspace = true
+jobslot.workspace = true
+num-bigint.workspace = true
+num-traits.workspace = true
+os_pipe.workspace = true
+petgraph.workspace = true
+serde_json.workspace = true
+serde.workspace = true
+tempfile.workspace = true
+vec_map.workspace = true
+which.workspace = true

 [dev-dependencies]
-trybuild = { workspace = true }
+trybuild.workspace = true

 [build-dependencies]
-fayalite-visit-gen = { workspace = true }
+fayalite-visit-gen.workspace = true

 [features]
 unstable-doc = []
+unstable-test-hasher = []

 [package.metadata.docs.rs]
 features = ["unstable-doc"]
--- a/crates/fayalite/build.rs
+++ b/crates/fayalite/build.rs
@ -4,6 +4,10 @@ use fayalite_visit_gen::parse_and_generate;
 use std::{env, fs, path::Path};

 fn main() {
+    println!("cargo::rustc-check-cfg=cfg(todo)");
+    println!("cargo::rustc-check-cfg=cfg(cfg_false_for_tests)");
+    println!("cargo::rustc-check-cfg=cfg(cfg_true_for_tests)");
+    println!("cargo::rustc-cfg=cfg_true_for_tests");
    let path = "visit_types.json";
    println!("cargo::rerun-if-changed={path}");
    println!("cargo::rerun-if-changed=build.rs");
--- a/crates/fayalite/examples/blinky.rs
+++ b/crates/fayalite/examples/blinky.rs
@ -1,11 +1,7 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use clap::Parser;
-use fayalite::{
-    cli,
-    clock::{Clock, ClockDomain},
-    hdl_module,
-    int::{DynUInt, DynUIntType, IntCmp, IntTypeTrait, UInt},
-    reset::{SyncReset, ToReset},
-};
+use fayalite::{cli, prelude::*};

 #[hdl_module]
 fn blinky(clock_frequency: u64) {
@ -19,21 +15,21 @@ fn blinky(clock_frequency: u64) {
        rst: rst.to_reset(),
    };
    let max_value = clock_frequency / 2 - 1;
-    let int_ty = DynUIntType::range_inclusive(0..=max_value);
+    let int_ty = UInt::range_inclusive(0..=max_value);
    #[hdl]
-    let counter: DynUInt = m.reg_builder().clock_domain(cd).reset(int_ty.literal(0));
+    let counter_reg: UInt = reg_builder().clock_domain(cd).reset(0u8.cast_to(int_ty));
    #[hdl]
-    let output_reg: UInt<1> = m.reg_builder().clock_domain(cd).reset_default();
+    let output_reg: Bool = reg_builder().clock_domain(cd).reset(false);
    #[hdl]
-    if counter.cmp_eq(max_value) {
-        m.connect_any(counter, 0u8);
-        m.connect(output_reg, !output_reg);
+    if counter_reg.cmp_eq(max_value) {
+        connect_any(counter_reg, 0u8);
+        connect(output_reg, !output_reg);
    } else {
-        m.connect_any(counter, counter + 1_hdl_u1);
+        connect_any(counter_reg, counter_reg + 1_hdl_u1);
    }
    #[hdl]
-    let led: UInt<1> = m.output();
-    m.connect(led, output_reg);
+    let led: Bool = m.output();
+    connect(led, output_reg);
 }

 #[derive(Parser)]
--- a/crates/fayalite/src/_docs.rs
+++ b/crates/fayalite/src/_docs.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 #![doc = include_str!("../README.md")]

 //!
@ -10,7 +12,7 @@
 //! function to add inputs/outputs and other components to that module.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt};
+//! # use fayalite::prelude::*;
 //! #
 //! #[hdl_module]
 //! pub fn example_module() {
@ -18,7 +20,7 @@
 //!     let an_input: UInt<10> = m.input(); // create an input that is a 10-bit unsigned integer
 //!     #[hdl]
 //!     let some_output: UInt<10> = m.output();
-//!     m.connect(some_output, an_input); // assigns the value of `an_input` to `some_output`
+//!     connect(some_output, an_input); // assigns the value of `an_input` to `some_output`
 //! }
 //! ```

--- a/crates/fayalite/src/_docs/modules.rs
+++ b/crates/fayalite/src/_docs/modules.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Fayalite Modules
 //!
 //! The [`#[hdl_module]`][`crate::hdl_module`] attribute is applied to a Rust
--- a/crates/fayalite/src/_docs/modules/extern_module.rs
+++ b/crates/fayalite/src/_docs/modules/extern_module.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! These are for when you want to use modules written in
 //! some other language, such as Verilog.
 //!
@ -11,8 +13,6 @@
 //!  * [`parameter_raw_verilog()`][`ModuleBuilder::parameter_raw_verilog`]
 //!  * [`parameter()`][`ModuleBuilder::parameter`]
 //!
-//! These use the [`ExternModule`][`crate::module::ExternModule`] tag type.
-//!
 //! [inputs/outputs]: crate::_docs::modules::module_bodies::hdl_let_statements::inputs_outputs

 #[allow(unused)]
--- a/crates/fayalite/src/_docs/modules/module_bodies.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Module Function Bodies
 //!
 //! The `#[hdl_module]` attribute lets you have statements/expressions with `#[hdl]` annotations
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs
@ -1,24 +1,26 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl]` Array Expressions
 //!
-//! `#[hdl]` can be used on Array Expressions to construct an [`Array<[T; N]>`][Array] expression:
+//! `#[hdl]` can be used on Array Expressions to construct an [`Array<[T; N]>`][type@Array] expression:
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, array::Array};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
 //! let v: UInt<8> = m.input();
 //! #[hdl]
-//! let w: Array<[UInt<8>; 4]> = m.wire();
-//! m.connect(
+//! let w: Array<UInt<8>, 4> = wire();
+//! connect(
 //!     w,
 //!     #[hdl]
-//!     [4_hdl_u8, v, 3_hdl_u8, (v + 7_hdl_u8).cast()] // you can make an array like this
+//!     [4_hdl_u8, v, 3_hdl_u8, (v + 7_hdl_u8).cast_to_static()] // you can make an array like this
 //! );
-//! m.connect(
+//! connect(
 //!     w,
 //!     #[hdl]
-//!     [(v + 1_hdl_u8).cast(); 4] // or you can make an array repeat like this
+//!     [(v + 1_hdl_u8).cast_to_static(); 4] // or you can make an array repeat like this
 //! );
 //! # }
 //! ```
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs
@ -1,10 +1,11 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl] if` Statements
 //!
 //! `#[hdl] if` statements behave similarly to Rust `if` statements, except they end up as muxes
 //! and stuff in the final hardware instead of being run when the fayalite module is being created.
 //!
-//! The condition of an `#[hdl] if` statement must have type [`UInt<1>`] or [`DynUInt`] with
-//! `width() == 1` or be an [expression][Expr] of one of those types.
+//! The condition of an `#[hdl] if` statement must have type [`Expr<Bool>`][Bool].
 //!
 //! `#[hdl] if` statements' bodies must evaluate to type `()` for now.
 //!
@ -14,7 +15,4 @@
 //! [match]: super::hdl_match_statements

 #[allow(unused)]
-use crate::{
-    expr::Expr,
-    int::{DynUInt, UInt},
-};
+use crate::int::Bool;
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs
@ -1,5 +1,8 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ## `#[hdl] let` statements

+pub mod destructuring;
 pub mod inputs_outputs;
 pub mod instances;
 pub mod memories;
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/destructuring.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/destructuring.rs
@ -0,0 +1,33 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+//! ### Destructuring Let
+//!
+//! You can use `#[hdl] let` to destructure types, similarly to Rust `let` statements with non-trivial patterns.
+//!
+//! `#[hdl] let` statements can only match one level of struct/tuple pattern for now,
+//! e.g. you can match with the pattern `MyStruct { a, b }`, but not `MyStruct { a, b: Struct2 { v } }`.
+//!
+//! ```
+//! # use fayalite::prelude::*;
+//! #[hdl]
+//! struct MyStruct {
+//!     a: UInt<8>,
+//!     b: Bool,
+//! }
+//!
+//! #[hdl_module]
+//! fn my_module() {
+//!     #[hdl]
+//!     let my_input: MyStruct = m.input();
+//!     #[hdl]
+//!     let my_output: UInt<8> = m.input();
+//!     #[hdl]
+//!     let MyStruct { a, b } = my_input;
+//!     #[hdl]
+//!     if b {
+//!         connect(my_output, a);
+//!     } else {
+//!         connect(my_output, 0_hdl_u8);
+//!     }
+//! }
+//! ```
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Inputs/Outputs
 //!
 //! Inputs/Outputs create a Rust variable with type [`Expr<T>`] where `T` is the type of the input/output.
@ -6,14 +8,14 @@
 //! so you should read it.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, expr::Expr, array::Array};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
 //! let my_input: UInt<10> = m.input();
 //! let _: Expr<UInt<10>> = my_input; // my_input has type Expr<UInt<10>>
 //! #[hdl]
-//! let my_output: Array<[UInt<10>; 3]> = m.output();
+//! let my_output: Array<UInt<10>, 3> = m.output();
 //! # }
 //! ```
 //!
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs
@ -1,18 +1,20 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Module Instances
 //!
 //! module instances are kinda like the hardware equivalent of calling a function,
 //! you can create them like so:
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, array::Array};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
-//! let my_instance = m.instance(some_module());
+//! let my_instance = instance(some_module());
 //! // now you can use `my_instance`'s inputs/outputs like so:
 //! #[hdl]
 //! let v: UInt<3> = m.input();
-//! m.connect(my_instance.a, v);
+//! connect(my_instance.a, v);
 //! #[hdl_module]
 //! fn some_module() {
 //!     #[hdl]
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Memories
 //!
 //! Memories are optimized for storing large amounts of data.
@ -7,12 +9,12 @@
 //!
 //! There are several different ways to create a memory:
 //!
-//! ## using [`ModuleBuilder::memory()`]
+//! ## using [`memory()`]
 //!
 //! This way you have to set the [`depth`][`MemBuilder::depth`] separately.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, clock::ClockDomain};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! // first, we need some IO
@ -25,45 +27,45 @@
 //!
 //! // now create the memory
 //! #[hdl]
-//! let mut my_memory = m.memory();
+//! let mut my_memory = memory();
 //! my_memory.depth(256); // the memory has 256 elements
 //!
 //! let read_port = my_memory.new_read_port();
 //!
 //! // connect up the read port
-//! m.connect_any(read_port.addr, read_addr);
-//! m.connect(read_port.en, 1_hdl_u1);
-//! m.connect(read_port.clk, cd.clk);
-//! m.connect(read_data, read_port.data);
+//! connect_any(read_port.addr, read_addr);
+//! connect(read_port.en, true);
+//! connect(read_port.clk, cd.clk);
+//! connect(read_data, read_port.data);
 //!
 //! // we need more IO for the write port
 //! #[hdl]
 //! let write_addr: UInt<8> = m.input();
 //! #[hdl]
-//! let do_write: UInt<1> = m.input();
+//! let do_write: Bool = m.input();
 //! #[hdl]
 //! let write_data: UInt<8> = m.input();
 //!
 //! let write_port = my_memory.new_write_port();
 //!
-//! m.connect_any(write_port.addr, write_addr);
-//! m.connect(write_port.en, do_write);
-//! m.connect(write_port.clk, cd.clk);
-//! m.connect(write_port.data, write_port.data);
-//! m.connect(write_port.mask, 1_hdl_u1);
+//! connect_any(write_port.addr, write_addr);
+//! connect(write_port.en, do_write);
+//! connect(write_port.clk, cd.clk);
+//! connect(write_port.data, write_port.data);
+//! connect(write_port.mask, true);
 //! # }
 //! ```
 //!
-//! ## using [`ModuleBuilder::memory_array()`]
+//! ## using [`memory_array()`]
 //!
 //! this allows you to specify the memory's underlying array type directly.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, memory::MemBuilder};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
-//! let mut my_memory: MemBuilder<[UInt<8>; 256]> = m.memory_array();
+//! let mut my_memory: MemBuilder<UInt<8>, ConstUsize<256>> = memory_array();
 //!
 //! let read_port = my_memory.new_read_port();
 //! // ...
@ -72,25 +74,22 @@
 //! # }
 //! ```
 //!
-//! ## using [`ModuleBuilder::memory_with_init()`]
+//! ## using [`memory_with_init()`]
 //!
 //! This allows you to deduce the memory's array type from the data used to initialize the memory.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! # #[hdl]
 //! # let read_addr: UInt<2> = m.input();
 //! #[hdl]
-//! let mut my_memory = m.memory_with_init(
-//!     #[hdl]
-//!     [0x12_hdl_u8, 0x34_hdl_u8, 0x56_hdl_u8, 0x78_hdl_u8],
-//! );
+//! let mut my_memory = memory_with_init([0x12_hdl_u8, 0x34_hdl_u8, 0x56_hdl_u8, 0x78_hdl_u8]);
 //!
 //! let read_port = my_memory.new_read_port();
 //! // note that `read_addr` is `UInt<2>` since the memory only has 4 elements
-//! m.connect_any(read_port.addr, read_addr);
+//! connect_any(read_port.addr, read_addr);
 //! // ...
 //! let write_port = my_memory.new_write_port();
 //! // ...
@ -98,4 +97,4 @@
 //! ```

 #[allow(unused)]
-use crate::{memory::MemBuilder, module::ModuleBuilder};
+use crate::prelude::*;
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Registers
 //!
 //! Registers are memory devices that will change their state only on a clock
@ -7,20 +9,23 @@
 //!
 //! Registers follow [connection semantics], which are unlike assignments in software, so you should read it.
 //!
+//! By convention, register names end in `_reg` -- this helps you tell which values are written
+//! immediately or on the next clock edge when connecting to them.
+//!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, array::Array, clock::ClockDomain};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! # #[hdl]
-//! # let v: UInt<1> = m.input();
+//! # let v: Bool = m.input();
 //! #[hdl]
 //! let cd: ClockDomain = m.input();
 //! #[hdl]
-//! let my_register: UInt<8> = m.reg_builder().clock_domain(cd).reset(8_hdl_u8);
+//! let my_reg: UInt<8> = reg_builder().clock_domain(cd).reset(8_hdl_u8);
 //! #[hdl]
 //! if v {
-//!     // my_register is only changed when both `v` is set and `cd`'s clock edge occurs.
-//!     m.connect(my_register, 0x45_hdl_u8);
+//!     // my_reg is only changed when both `v` is set and `cd`'s clock edge occurs.
+//!     connect(my_reg, 0x45_hdl_u8);
 //! }
 //! # }
 //! ```
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs
@ -1,27 +1,29 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Wires
 //!
 //! Wires are kinda like variables, but unlike registers,
 //! they have no memory (they're combinatorial).
-//! You must [connect][`ModuleBuilder::connect`] to all wires, so they have a defined value.
+//! You must [connect] to all wires, so they have a defined value.
 //!
 //! Wires create a Rust variable with type [`Expr<T>`] where `T` is the type of the wire.
 //!
 //! Wires follow [connection semantics], which are unlike assignments in software, so you should read it.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, array::Array, clock::ClockDomain};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! # #[hdl]
-//! # let v: UInt<1> = m.input();
+//! # let v: Bool = m.input();
 //! #[hdl]
-//! let my_wire: UInt<8> = m.wire();
+//! let my_wire: UInt<8> = wire();
 //! #[hdl]
 //! if v {
-//!     m.connect(my_wire, 0x45_hdl_u8);
+//!     connect(my_wire, 0x45_hdl_u8);
 //! } else {
 //!     // wires must be connected to under all conditions
-//!     m.connect(my_wire, 0x23_hdl_u8);
+//!     connect(my_wire, 0x23_hdl_u8);
 //! }
 //! # }
 //! ```
@ -29,4 +31,4 @@
 //! [connection semantics]: crate::_docs::semantics::connection_semantics

 #[allow(unused)]
-use crate::{expr::Expr, module::ModuleBuilder};
+use crate::prelude::*;
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs
@ -1,9 +1,10 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `_hdl`-suffixed literals
 //!
 //! You can have integer literals with an arbitrary number of bits like so:
 //!
-//! `_hdl`-suffixed literals have type [`Expr<UInt<N>>`] or [`Expr<SInt<N>>`]
-//! ... which are basically just [`UInt<N>`] or [`SInt<N>`] converted to an expression.
+//! `_hdl`-suffixed literals have type [`Expr<UInt<N>>`] or [`Expr<SInt<N>>`].
 //!
 //! ```
 //! # #[fayalite::hdl_module]
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl] match` Statements
 //!
 //! `#[hdl] match` statements behave similarly to Rust `match` statements, except they end up as muxes
@ -5,5 +7,5 @@
 //!
 //! `#[hdl] match` statements' bodies must evaluate to type `()` for now.
 //!
-//! `#[hdl] match` statements can only match one level of struct/enum pattern for now,
-//! e.g. you can match with the pattern `Some(v)`, but not `Some(Some(_))`.
+//! `#[hdl] match` statements can only match one level of struct/tuple/enum pattern for now,
+//! e.g. you can match with the pattern `HdlSome(v)`, but not `HdlSome(HdlSome(_))`.
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs
@ -1,28 +1,27 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl]` Struct/Variant Expressions
 //!
 //! Note: Structs are also known as [Bundles] when used in Fayalite, the Bundle name comes from [FIRRTL].
 //!
-//! [Bundles]: crate::bundle::BundleValue
+//! [Bundles]: crate::bundle::BundleType
 //! [FIRRTL]: https://github.com/chipsalliance/firrtl-spec
 //!
-//! `#[hdl]` can be used on Struct/Variant Expressions to construct a value of that
-//! struct/variant's type. They can also be used on tuples.
+//! `#[hdl]` can be used on Struct Expressions to construct a value of that
+//! struct's type. They can also be used on tuples.
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt, array::Array, ty::Value};
-//! #[derive(Value, Clone, PartialEq, Eq, Hash, Debug)]
-//! #[hdl(static)]
+//! # use fayalite::prelude::*;
+//! #[hdl]
 //! pub struct MyStruct {
 //!     pub a: UInt<8>,
 //!     pub b: UInt<16>,
 //! }
 //!
-//! #[derive(Value, Clone, PartialEq, Eq, Hash, Debug)]
+//! #[hdl]
 //! pub enum MyEnum {
 //!     A,
-//!     B {
-//!         v: UInt<32>,
-//!     },
+//!     B(UInt<32>),
 //! }
 //!
 //! # #[hdl_module]
@ -30,8 +29,8 @@
 //! #[hdl]
 //! let v: UInt<8> = m.input();
 //! #[hdl]
-//! let my_struct: MyStruct = m.wire();
-//! m.connect(
+//! let my_struct: MyStruct = wire();
+//! connect(
 //!     my_struct,
 //!     #[hdl]
 //!     MyStruct {
@ -40,15 +39,14 @@
 //!     },
 //! );
 //! #[hdl]
-//! let my_enum: MyEnum = m.wire();
-//! m.connect(
+//! let my_enum: MyEnum = wire();
+//! connect(
 //!     my_enum,
-//!     #[hdl]
-//!     MyEnum::B { v: 12345678_hdl_u32 },
+//!     MyEnum.B(12345678_hdl_u32),
 //! );
 //! #[hdl]
-//! let some_tuple: (UInt<4>, UInt<12>) = m.wire();
-//! m.connect(
+//! let some_tuple: (UInt<4>, UInt<12>) = wire();
+//! connect(
 //!     some_tuple,
 //!     #[hdl]
 //!     (12_hdl_u4, 3421_hdl_u12),
@ -57,4 +55,4 @@
 //! ```

 #[allow(unused)]
-use crate::array::Array;
+use crate::prelude::*;
--- a/crates/fayalite/src/_docs/modules/normal_module.rs
+++ b/crates/fayalite/src/_docs/modules/normal_module.rs
@ -1,6 +1,6 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Normal Modules
 //!
-//! These use the [`NormalModule`][`crate::module::NormalModule`] tag type.
-//!
 //! See also: [Extern Modules][`super::extern_module`]
 //! See also: [Module Bodies][`super::module_bodies`]
--- a/crates/fayalite/src/_docs/semantics.rs
+++ b/crates/fayalite/src/_docs/semantics.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Fayalite Semantics
 //!
 //! Fayalite's semantics are based on [FIRRTL]. Due to their significance, some of the semantics are also documented here.
--- a/crates/fayalite/src/_docs/semantics/connection_semantics.rs
+++ b/crates/fayalite/src/_docs/semantics/connection_semantics.rs
@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Connection Semantics
 //!
 //! Fayalite's connection semantics are unlike assignments in software, so be careful!
@ -20,62 +22,60 @@
 //! Connection Semantics Example:
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
-//! let a: UInt<8> = m.wire();
+//! let a: UInt<8> = wire();
 //! #[hdl]
 //! let b: UInt<8> = m.output();
 //!
 //! // doesn't actually affect anything, since `a` is completely overwritten later
-//! m.connect(a, 5_hdl_u8);
+//! connect(a, 5_hdl_u8);
 //!
 //! // here `a` has value `7` since the last connection assigns
 //! // `7` to `a`, so `b` has value `7` too.
-//! m.connect(b, a);
+//! connect(b, a);
 //!
 //! // this is the last `connect` to `a`, so this `connect` determines `a`'s value
-//! m.connect(a, 7_hdl_u8);
+//! connect(a, 7_hdl_u8);
 //! # }
 //! ```
 //!
 //! # Conditional Connection Semantics
 //!
 //! ```
-//! # use fayalite::{hdl_module, int::UInt};
+//! # use fayalite::prelude::*;
 //! # #[hdl_module]
 //! # fn module() {
 //! #[hdl]
-//! let cond: UInt<1> = m.input();
+//! let cond: Bool = m.input();
 //! #[hdl]
-//! let a: UInt<8> = m.wire();
+//! let a: UInt<8> = wire();
 //! #[hdl]
 //! let b: UInt<8> = m.output();
 //!
 //! // this is the last `connect` to `a` when `cond` is `0`
-//! m.connect(a, 5_hdl_u8);
+//! connect(a, 5_hdl_u8);
 //!
 //! // here `a` has value `7` if `cond` is `1` since the last connection assigns
 //! // `7` to `a`, so `b` has value `7` too, otherwise `a` (and therefore `b`)
 //! // have value `5` since then the connection assigning `7` is in a
 //! // conditional block where the condition doesn't hold.
-//! m.connect(b, a);
+//! connect(b, a);
 //!
 //! #[hdl]
 //! if cond {
 //!     // this is the last `connect` to `a` when `cond` is `1`
-//!     m.connect(a, 7_hdl_u8);
+//!     connect(a, 7_hdl_u8);
 //! }
 //! # }
 //! ```
 //!
 //! [conditional block]: self#conditional-connection-semantics
-//! [`connect()`]: ModuleBuilder::connect
-//! [`connect_any()`]: ModuleBuilder::connect_any
 //! [wire]: crate::_docs::modules::module_bodies::hdl_let_statements::wires
 //! [if]: crate::_docs::modules::module_bodies::hdl_if_statements
 //! [FIRRTL]: https://github.com/chipsalliance/firrtl-spec

 #[allow(unused)]
-use crate::module::ModuleBuilder;
+use crate::prelude::*;
--- a/crates/fayalite/src/annotations.rs
+++ b/crates/fayalite/src/annotations.rs
@ -1,17 +1,18 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    expr::Target,
+    expr::target::Target,
    intern::{Intern, Interned},
 };
 use serde::{Deserialize, Serialize};
 use std::{
    fmt,
    hash::{Hash, Hasher},
+    iter::FusedIterator,
    ops::Deref,
 };

-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct CustomFirrtlAnnotationFieldsImpl {
    value: serde_json::Map<String, serde_json::Value>,
    serialized: Interned<str>,
@ -118,11 +119,87 @@ pub struct CustomFirrtlAnnotation {
    pub additional_fields: CustomFirrtlAnnotationFields,
 }

-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
-#[non_exhaustive]
-pub enum Annotation {
-    DontTouch,
-    CustomFirrtl(CustomFirrtlAnnotation),
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, Serialize, Deserialize)]
+pub struct DontTouchAnnotation;
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, Serialize, Deserialize)]
+pub struct SVAttributeAnnotation {
+    pub text: Interned<str>,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, Serialize, Deserialize)]
+pub struct BlackBoxInlineAnnotation {
+    pub path: Interned<str>,
+    pub text: Interned<str>,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, Serialize, Deserialize)]
+pub struct BlackBoxPathAnnotation {
+    pub path: Interned<str>,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash, Serialize, Deserialize)]
+pub struct DocStringAnnotation {
+    pub text: Interned<str>,
+}
+
+macro_rules! make_annotation_enum {
+    (
+        $(#[$meta:meta])*
+        $vis:vis enum $Annotation:ident {
+            $($Variant:ident($T:ident),)*
+        }
+    ) => {
+        $(#[$meta])*
+        $vis enum $Annotation {
+            $($Variant($T),)*
+        }
+
+        $(impl IntoAnnotations for $T {
+            type IntoAnnotations = [$Annotation; 1];
+
+            fn into_annotations(self) -> Self::IntoAnnotations {
+                [$Annotation::$Variant(self)]
+            }
+        }
+
+        impl IntoAnnotations for &'_ $T {
+            type IntoAnnotations = [$Annotation; 1];
+
+            fn into_annotations(self) -> Self::IntoAnnotations {
+                [$Annotation::$Variant(*self)]
+            }
+        }
+
+        impl IntoAnnotations for &'_ mut $T {
+            type IntoAnnotations = [$Annotation; 1];
+
+            fn into_annotations(self) -> Self::IntoAnnotations {
+                [$Annotation::$Variant(*self)]
+            }
+        }
+
+        impl IntoAnnotations for Box<$T> {
+            type IntoAnnotations = [$Annotation; 1];
+
+            fn into_annotations(self) -> Self::IntoAnnotations {
+                [$Annotation::$Variant(*self)]
+            }
+        })*
+    };
+}
+
+make_annotation_enum! {
+    #[derive(Clone, PartialEq, Eq, Hash, Debug)]
+    #[non_exhaustive]
+    pub enum Annotation {
+        DontTouch(DontTouchAnnotation),
+        SVAttribute(SVAttributeAnnotation),
+        BlackBoxInline(BlackBoxInlineAnnotation),
+        BlackBoxPath(BlackBoxPathAnnotation),
+        DocString(DocStringAnnotation),
+        CustomFirrtl(CustomFirrtlAnnotation),
+    }
 }

 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
@ -187,10 +264,70 @@ impl IntoAnnotations for &'_ mut Annotation {
    }
 }

-impl<T: IntoIterator<Item = Annotation>> IntoAnnotations for T {
-    type IntoAnnotations = Self;
+pub struct IterIntoAnnotations<T: Iterator<Item: IntoAnnotations>> {
+    outer: T,
+    inner: Option<<<T::Item as IntoAnnotations>::IntoAnnotations as IntoIterator>::IntoIter>,
+}

-    fn into_annotations(self) -> Self::IntoAnnotations {
-        self
+impl<T: Iterator<Item: IntoAnnotations>> Iterator for IterIntoAnnotations<T> {
+    type Item = Annotation;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some(inner) = &mut self.inner {
+                let Some(retval) = inner.next() else {
+                    self.inner = None;
+                    continue;
+                };
+                return Some(retval);
+            } else {
+                self.inner = Some(self.outer.next()?.into_annotations().into_iter());
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if let (0, Some(0)) = self.outer.size_hint() {
+            self.inner
+                .as_ref()
+                .map(|v| v.size_hint())
+                .unwrap_or((0, Some(0)))
+        } else {
+            (
+                self.inner.as_ref().map(|v| v.size_hint().0).unwrap_or(0),
+                None,
+            )
+        }
+    }
+
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.inner
+            .into_iter()
+            .chain(self.outer.map(|v| v.into_annotations().into_iter()))
+            .flatten()
+            .fold(init, f)
+    }
+}
+
+impl<
+        T: FusedIterator<
+            Item: IntoAnnotations<IntoAnnotations: IntoIterator<IntoIter: FusedIterator>>,
+        >,
+    > FusedIterator for IterIntoAnnotations<T>
+{
+}
+
+impl<T: IntoIterator<Item: IntoAnnotations>> IntoAnnotations for T {
+    type IntoAnnotations = IterIntoAnnotations<T::IntoIter>;
+
+    fn into_annotations(self) -> Self::IntoAnnotations {
+        IterIntoAnnotations {
+            outer: self.into_iter(),
+            inner: None,
+        }
    }
 }
--- a/crates/fayalite/src/array.rs
+++ b/crates/fayalite/src/array.rs
--- a/crates/fayalite/src/bundle.rs
+++ b/crates/fayalite/src/bundle.rs
--- a/crates/fayalite/src/cli.rs
+++ b/crates/fayalite/src/cli.rs
@ -1,15 +1,27 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{
-    bundle::{BundleType, BundleValue, DynBundle},
-    firrtl,
+    bundle::{Bundle, BundleType},
+    firrtl::{self, ExportOptions},
    intern::Interned,
    module::Module,
+    util::{job_server::AcquiredJob, streaming_read_utf8::streaming_read_utf8},
 };
 use clap::{
    builder::{OsStringValueParser, TypedValueParser},
-    Args, Parser, Subcommand, ValueEnum, ValueHint,
+    Parser, Subcommand, ValueEnum, ValueHint,
 };
 use eyre::{eyre, Report};
-use std::{error, ffi::OsString, fmt, io, path::PathBuf, process};
+use serde::{Deserialize, Serialize};
+use std::{
+    error,
+    ffi::OsString,
+    fmt::{self, Write},
+    fs, io, mem,
+    path::{Path, PathBuf},
+    process,
+};
+use tempfile::TempDir;

 pub type Result<T = (), E = CliError> = std::result::Result<T, E>;

@ -37,80 +49,157 @@ impl From<io::Error> for CliError {

 pub trait RunPhase<Arg> {
    type Output;
-    fn run(&self, arg: Arg) -> Result<Self::Output>;
+    fn run(&self, arg: Arg) -> Result<Self::Output> {
+        self.run_with_job(arg, &mut AcquiredJob::acquire())
+    }
+    fn run_with_job(&self, arg: Arg, acquired_job: &mut AcquiredJob) -> Result<Self::Output>;
 }

-#[derive(Args, Debug)]
+#[derive(Parser, Debug, Clone)]
 #[non_exhaustive]
 pub struct BaseArgs {
    /// the directory to put the generated main output file and associated files in
-    #[arg(short, long, value_hint = ValueHint::DirPath)]
-    pub output: PathBuf,
+    #[arg(short, long, value_hint = ValueHint::DirPath, required = true)]
+    pub output: Option<PathBuf>,
    /// the stem of the generated main output file, e.g. to get foo.v, pass --file-stem=foo
    #[arg(long)]
    pub file_stem: Option<String>,
+    #[arg(long, env = "FAYALITE_KEEP_TEMP_DIR")]
+    pub keep_temp_dir: bool,
+    #[arg(skip = false)]
+    pub redirect_output_for_rust_test: bool,
 }

 impl BaseArgs {
-    pub fn to_firrtl_file_backend(&self) -> firrtl::FileBackend {
-        firrtl::FileBackend {
-            dir_path: self.output.clone(),
-            top_fir_file_stem: self.file_stem.clone(),
+    fn make_firrtl_file_backend(&self) -> Result<(firrtl::FileBackend, Option<TempDir>)> {
+        let (dir_path, temp_dir) = match &self.output {
+            Some(output) => (output.clone(), None),
+            None => {
+                let temp_dir = TempDir::new()?;
+                if self.keep_temp_dir {
+                    let temp_dir = temp_dir.into_path();
+                    println!("created temporary directory: {}", temp_dir.display());
+                    (temp_dir, None)
+                } else {
+                    (temp_dir.path().to_path_buf(), Some(temp_dir))
+                }
+            }
+        };
+        Ok((
+            firrtl::FileBackend {
+                dir_path,
+                top_fir_file_stem: self.file_stem.clone(),
+                circuit_name: None,
+            },
+            temp_dir,
+        ))
+    }
+    /// handles possibly redirecting the command's output for Rust tests
+    pub fn run_external_command(
+        &self,
+        _acquired_job: &mut AcquiredJob,
+        mut command: process::Command,
+        mut captured_output: Option<&mut String>,
+    ) -> io::Result<process::ExitStatus> {
+        if self.redirect_output_for_rust_test || captured_output.is_some() {
+            let (reader, writer) = os_pipe::pipe()?;
+            let mut reader = io::BufReader::new(reader);
+            command.stderr(writer.try_clone()?);
+            command.stdout(writer); // must not leave writer around after spawning child
+            command.stdin(process::Stdio::null());
+            let mut child = command.spawn()?;
+            drop(command); // close writers
+            Ok(loop {
+                let status = child.try_wait()?;
+                streaming_read_utf8(&mut reader, |s| {
+                    if let Some(captured_output) = captured_output.as_deref_mut() {
+                        captured_output.push_str(s);
+                    }
+                    // use print! so output goes to Rust test output capture
+                    print!("{s}");
+                    io::Result::Ok(())
+                })?;
+                if let Some(status) = status {
+                    break status;
+                }
+            })
+        } else {
+            command.status()
        }
    }
 }

-#[derive(Args, Debug)]
+#[derive(Parser, Debug, Clone)]
 #[non_exhaustive]
 pub struct FirrtlArgs {
    #[command(flatten)]
    pub base: BaseArgs,
+    #[command(flatten)]
+    pub export_options: ExportOptions,
 }

 #[derive(Debug)]
 #[non_exhaustive]
 pub struct FirrtlOutput {
    pub file_stem: String,
+    pub top_module: String,
+    pub output_dir: PathBuf,
+    pub temp_dir: Option<TempDir>,
 }

 impl FirrtlOutput {
-    pub fn firrtl_file(&self, args: &FirrtlArgs) -> PathBuf {
-        let mut retval = args.base.output.join(&self.file_stem);
-        retval.set_extension("fir");
+    pub fn file_with_ext(&self, ext: &str) -> PathBuf {
+        let mut retval = self.output_dir.join(&self.file_stem);
+        retval.set_extension(ext);
        retval
    }
+    pub fn firrtl_file(&self) -> PathBuf {
+        self.file_with_ext("fir")
+    }
 }

 impl FirrtlArgs {
-    fn run_impl(&self, top_module: Module<DynBundle>) -> Result<FirrtlOutput> {
+    fn run_impl(
+        &self,
+        top_module: Module<Bundle>,
+        _acquired_job: &mut AcquiredJob,
+    ) -> Result<FirrtlOutput> {
+        let (file_backend, temp_dir) = self.base.make_firrtl_file_backend()?;
        let firrtl::FileBackend {
-            top_fir_file_stem, ..
-        } = firrtl::export(self.base.to_firrtl_file_backend(), &top_module)?;
+            top_fir_file_stem,
+            circuit_name,
+            dir_path,
+        } = firrtl::export(file_backend, &top_module, self.export_options)?;
        Ok(FirrtlOutput {
            file_stem: top_fir_file_stem.expect(
                "export is known to set the file stem from the circuit name if not provided",
            ),
+            top_module: circuit_name.expect("export is known to set the circuit name"),
+            output_dir: dir_path,
+            temp_dir,
        })
    }
 }

-impl<T: BundleValue> RunPhase<Module<T>> for FirrtlArgs
-where
-    T::Type: BundleType<Value = T>,
-{
+impl<T: BundleType> RunPhase<Module<T>> for FirrtlArgs {
    type Output = FirrtlOutput;
-    fn run(&self, top_module: Module<T>) -> Result<Self::Output> {
-        self.run_impl(top_module.canonical())
+    fn run_with_job(
+        &self,
+        top_module: Module<T>,
+        acquired_job: &mut AcquiredJob,
+    ) -> Result<Self::Output> {
+        self.run_impl(top_module.canonical(), acquired_job)
    }
 }

-impl<T: BundleValue> RunPhase<Interned<Module<T>>> for FirrtlArgs
-where
-    T::Type: BundleType<Value = T>,
-{
+impl<T: BundleType> RunPhase<Interned<Module<T>>> for FirrtlArgs {
    type Output = FirrtlOutput;
-    fn run(&self, top_module: Interned<Module<T>>) -> Result<Self::Output> {
-        self.run(*top_module)
+    fn run_with_job(
+        &self,
+        top_module: Interned<Module<T>>,
+        acquired_job: &mut AcquiredJob,
+    ) -> Result<Self::Output> {
+        self.run_with_job(*top_module, acquired_job)
    }
 }

@ -126,7 +215,22 @@ pub enum VerilogDialect {
    Yosys,
 }

+impl fmt::Display for VerilogDialect {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
 impl VerilogDialect {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            VerilogDialect::Questa => "questa",
+            VerilogDialect::Spyglass => "spyglass",
+            VerilogDialect::Verilator => "verilator",
+            VerilogDialect::Vivado => "vivado",
+            VerilogDialect::Yosys => "yosys",
+        }
+    }
    pub fn firtool_extra_args(self) -> &'static [&'static str] {
        match self {
            VerilogDialect::Questa => &["--lowering-options=emitWireInPorts"],
@ -144,7 +248,7 @@ impl VerilogDialect {
    }
 }

-#[derive(Args, Debug)]
+#[derive(Parser, Debug, Clone)]
 #[non_exhaustive]
 pub struct VerilogArgs {
    #[command(flatten)]
@ -154,7 +258,7 @@ pub struct VerilogArgs {
        default_value = "firtool",
        env = "FIRTOOL",
        value_hint = ValueHint::CommandName,
-        value_parser = OsStringValueParser::new().try_map(which::which)
+        value_parser = OsStringValueParser::new().try_map(which)
    )]
    pub firtool: PathBuf,
    #[arg(long)]
@ -162,39 +266,94 @@ pub struct VerilogArgs {
    /// adapt the generated Verilog for a particular toolchain
    #[arg(long)]
    pub verilog_dialect: Option<VerilogDialect>,
+    #[arg(long, short = 'g')]
+    pub debug: bool,
 }

 #[derive(Debug)]
 #[non_exhaustive]
 pub struct VerilogOutput {
    pub firrtl: FirrtlOutput,
+    pub verilog_files: Vec<PathBuf>,
+    pub contents_hash: Option<blake3::Hash>,
 }

 impl VerilogOutput {
-    pub fn verilog_file(&self, args: &VerilogArgs) -> PathBuf {
-        let mut retval = args.firrtl.base.output.join(&self.firrtl.file_stem);
-        retval.set_extension("v");
-        retval
+    pub fn main_verilog_file(&self) -> PathBuf {
+        self.firrtl.file_with_ext("v")
+    }
+    fn unadjusted_verilog_file(&self) -> PathBuf {
+        self.firrtl.file_with_ext("unadjusted.v")
    }
 }

 impl VerilogArgs {
-    fn run_impl(&self, firrtl_output: FirrtlOutput) -> Result<VerilogOutput> {
+    fn process_unadjusted_verilog_file(&self, mut output: VerilogOutput) -> Result<VerilogOutput> {
+        let input = fs::read_to_string(output.unadjusted_verilog_file())?;
+        let file_separator_prefix = "\n// ----- 8< ----- FILE \"";
+        let file_separator_suffix = "\" ----- 8< -----\n\n";
+        let mut input = &*input;
+        output.contents_hash = Some(blake3::hash(input.as_bytes()));
+        let main_verilog_file = output.main_verilog_file();
+        let mut file_name: Option<&Path> = Some(&main_verilog_file);
+        loop {
+            let (chunk, next_file_name) = if let Some((chunk, rest)) =
+                input.split_once(file_separator_prefix)
+            {
+                let Some((next_file_name, rest)) = rest.split_once(file_separator_suffix) else {
+                    return Err(CliError(eyre!("parsing firtool's output failed: found {file_separator_prefix:?} but no {file_separator_suffix:?}")));
+                };
+                input = rest;
+                (chunk, Some(next_file_name.as_ref()))
+            } else {
+                (mem::take(&mut input), None)
+            };
+            let Some(file_name) = mem::replace(&mut file_name, next_file_name) else {
+                break;
+            };
+            let file_name = output.firrtl.output_dir.join(file_name);
+            fs::write(&file_name, chunk)?;
+            if let Some(extension) = file_name.extension() {
+                if extension == "v" || extension == "sv" {
+                    output.verilog_files.push(file_name);
+                }
+            }
+        }
+        Ok(output)
+    }
+    fn run_impl(
+        &self,
+        firrtl_output: FirrtlOutput,
+        acquired_job: &mut AcquiredJob,
+    ) -> Result<VerilogOutput> {
+        let Self {
+            firrtl,
+            firtool,
+            firtool_extra_args,
+            verilog_dialect,
+            debug,
+        } = self;
        let output = VerilogOutput {
            firrtl: firrtl_output,
+            verilog_files: vec![],
+            contents_hash: None,
        };
-        let mut cmd = process::Command::new(&self.firtool);
-        cmd.arg(output.firrtl.firrtl_file(&self.firrtl));
+        let mut cmd = process::Command::new(firtool);
+        cmd.arg(output.firrtl.firrtl_file());
        cmd.arg("-o");
-        cmd.arg(output.verilog_file(self));
-        if let Some(dialect) = self.verilog_dialect {
+        cmd.arg(output.unadjusted_verilog_file());
+        if *debug {
+            cmd.arg("-g");
+            cmd.arg("--preserve-values=all");
+        }
+        if let Some(dialect) = verilog_dialect {
            cmd.args(dialect.firtool_extra_args());
        }
-        cmd.args(&self.firtool_extra_args);
-        cmd.current_dir(&self.firrtl.base.output);
-        let status = cmd.status()?;
+        cmd.args(firtool_extra_args);
+        cmd.current_dir(&output.firrtl.output_dir);
+        let status = firrtl.base.run_external_command(acquired_job, cmd, None)?;
        if status.success() {
-            Ok(output)
+            self.process_unadjusted_verilog_file(output)
        } else {
            Err(CliError(eyre!(
                "running {} failed: {status}",
@ -209,9 +368,323 @@ where
    FirrtlArgs: RunPhase<Arg, Output = FirrtlOutput>,
 {
    type Output = VerilogOutput;
-    fn run(&self, arg: Arg) -> Result<Self::Output> {
-        let firrtl_output = self.firrtl.run(arg)?;
-        self.run_impl(firrtl_output)
+    fn run_with_job(&self, arg: Arg, acquired_job: &mut AcquiredJob) -> Result<Self::Output> {
+        let firrtl_output = self.firrtl.run_with_job(arg, acquired_job)?;
+        self.run_impl(firrtl_output, acquired_job)
+    }
+}
+
+#[derive(ValueEnum, Copy, Clone, Debug, PartialEq, Eq, Hash, Default)]
+#[non_exhaustive]
+pub enum FormalMode {
+    #[default]
+    BMC,
+    Prove,
+    Live,
+    Cover,
+}
+
+impl FormalMode {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            FormalMode::BMC => "bmc",
+            FormalMode::Prove => "prove",
+            FormalMode::Live => "live",
+            FormalMode::Cover => "cover",
+        }
+    }
+}
+
+impl fmt::Display for FormalMode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+#[derive(Clone)]
+struct FormalAdjustArgs;
+
+impl clap::FromArgMatches for FormalAdjustArgs {
+    fn from_arg_matches(_matches: &clap::ArgMatches) -> Result<Self, clap::Error> {
+        Ok(Self)
+    }
+
+    fn update_from_arg_matches(&mut self, _matches: &clap::ArgMatches) -> Result<(), clap::Error> {
+        Ok(())
+    }
+}
+
+impl clap::Args for FormalAdjustArgs {
+    fn augment_args(cmd: clap::Command) -> clap::Command {
+        cmd.mut_arg("output", |arg| arg.required(false))
+            .mut_arg("verilog_dialect", |arg| {
+                arg.default_value(VerilogDialect::Yosys.to_string())
+                    .hide(true)
+            })
+    }
+
+    fn augment_args_for_update(cmd: clap::Command) -> clap::Command {
+        Self::augment_args(cmd)
+    }
+}
+
+fn which(v: std::ffi::OsString) -> which::Result<PathBuf> {
+    #[cfg(not(miri))]
+    return which::which(v);
+    #[cfg(miri)]
+    return Ok(Path::new("/").join(v));
+}
+
+#[derive(Parser, Clone)]
+#[non_exhaustive]
+pub struct FormalArgs {
+    #[command(flatten)]
+    pub verilog: VerilogArgs,
+    #[arg(
+        long,
+        default_value = "sby",
+        env = "SBY",
+        value_hint = ValueHint::CommandName,
+        value_parser = OsStringValueParser::new().try_map(which)
+    )]
+    pub sby: PathBuf,
+    #[arg(long)]
+    pub sby_extra_args: Vec<String>,
+    #[arg(long, default_value_t)]
+    pub mode: FormalMode,
+    #[arg(long, default_value_t = Self::DEFAULT_DEPTH)]
+    pub depth: u64,
+    #[arg(long, default_value = "z3")]
+    pub solver: String,
+    #[arg(long)]
+    pub smtbmc_extra_args: Vec<String>,
+    #[arg(long, default_value_t = true, env = "FAYALITE_CACHE_RESULTS")]
+    pub cache_results: bool,
+    #[command(flatten)]
+    _formal_adjust_args: FormalAdjustArgs,
+}
+
+impl fmt::Debug for FormalArgs {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self {
+            verilog,
+            sby,
+            sby_extra_args,
+            mode,
+            depth,
+            solver,
+            smtbmc_extra_args,
+            cache_results,
+            _formal_adjust_args: _,
+        } = self;
+        f.debug_struct("FormalArgs")
+            .field("verilog", verilog)
+            .field("sby", sby)
+            .field("sby_extra_args", sby_extra_args)
+            .field("mode", mode)
+            .field("depth", depth)
+            .field("solver", solver)
+            .field("smtbmc_extra_args", smtbmc_extra_args)
+            .field("cache_results", cache_results)
+            .finish_non_exhaustive()
+    }
+}
+
+impl FormalArgs {
+    pub const DEFAULT_DEPTH: u64 = 20;
+}
+
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct FormalOutput {
+    pub verilog: VerilogOutput,
+}
+
+impl FormalOutput {
+    pub fn sby_file(&self) -> PathBuf {
+        self.verilog.firrtl.file_with_ext("sby")
+    }
+    pub fn cache_file(&self) -> PathBuf {
+        self.verilog.firrtl.file_with_ext("cache.json")
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[non_exhaustive]
+pub struct FormalCacheOutput {}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[non_exhaustive]
+pub enum FormalCacheVersion {
+    V1,
+}
+
+impl FormalCacheVersion {
+    pub const CURRENT: Self = Self::V1;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[non_exhaustive]
+pub struct FormalCache {
+    pub version: FormalCacheVersion,
+    pub contents_hash: blake3::Hash,
+    pub stdout_stderr: String,
+    pub result: Result<FormalCacheOutput, String>,
+}
+
+impl FormalCache {
+    pub fn new(
+        version: FormalCacheVersion,
+        contents_hash: blake3::Hash,
+        stdout_stderr: String,
+        result: Result<FormalCacheOutput, String>,
+    ) -> Self {
+        Self {
+            version,
+            contents_hash,
+            stdout_stderr,
+            result,
+        }
+    }
+}
+
+impl FormalArgs {
+    fn sby_contents(&self, output: &FormalOutput) -> Result<String> {
+        let Self {
+            verilog: _,
+            sby: _,
+            sby_extra_args: _,
+            mode,
+            depth,
+            smtbmc_extra_args,
+            solver,
+            cache_results: _,
+            _formal_adjust_args: _,
+        } = self;
+        let smtbmc_options = smtbmc_extra_args.join(" ");
+        let top_module = &output.verilog.firrtl.top_module;
+        let mut retval = format!(
+            "[options]\n\
+            mode {mode}\n\
+            depth {depth}\n\
+            wait on\n\
+            \n\
+            [engines]\n\
+            smtbmc {solver} -- -- {smtbmc_options}\n\
+            \n\
+            [script]\n"
+        );
+        for verilog_file in &output.verilog.verilog_files {
+            let verilog_file = verilog_file
+                .to_str()
+                .ok_or_else(|| CliError(eyre!("verilog file path is not UTF-8")))?;
+            if verilog_file.contains(|ch: char| {
+                (ch != ' ' && ch != '\t' && ch.is_ascii_whitespace()) || ch == '"'
+            }) {
+                return Err(CliError(eyre!(
+                    "verilog file path contains characters that aren't permitted"
+                )));
+            }
+            writeln!(retval, "read_verilog -sv -formal \"{verilog_file}\"").unwrap();
+        }
+        // workaround for wires disappearing -- set `keep` on all wires
+        writeln!(retval, "hierarchy -top {top_module}").unwrap();
+        writeln!(retval, "proc").unwrap();
+        writeln!(retval, "setattr -set keep 1 w:\\*").unwrap();
+        writeln!(retval, "prep").unwrap();
+        Ok(retval)
+    }
+    fn run_impl(
+        &self,
+        verilog_output: VerilogOutput,
+        acquired_job: &mut AcquiredJob,
+    ) -> Result<FormalOutput> {
+        let output = FormalOutput {
+            verilog: verilog_output,
+        };
+        let sby_file = output.sby_file();
+        let sby_contents = self.sby_contents(&output)?;
+        let contents_hash = output.verilog.contents_hash.map(|verilog_hash| {
+            let mut hasher = blake3::Hasher::new();
+            hasher.update(verilog_hash.as_bytes());
+            hasher.update(sby_contents.as_bytes());
+            hasher.update(&(self.sby_extra_args.len() as u64).to_le_bytes());
+            for sby_extra_arg in self.sby_extra_args.iter() {
+                hasher.update(&(sby_extra_arg.len() as u64).to_le_bytes());
+                hasher.update(sby_extra_arg.as_bytes());
+            }
+            hasher.finalize()
+        });
+        std::fs::write(&sby_file, sby_contents)?;
+        let mut cmd = process::Command::new(&self.sby);
+        cmd.arg("-j1"); // sby seems not to respect job count in parallel mode
+        cmd.arg("-f");
+        cmd.arg(sby_file.file_name().unwrap());
+        cmd.args(&self.sby_extra_args);
+        cmd.current_dir(&output.verilog.firrtl.output_dir);
+        let mut captured_output = String::new();
+        let cache_file = output.cache_file();
+        let do_cache = if let Some(contents_hash) = contents_hash.filter(|_| self.cache_results) {
+            if let Some(FormalCache {
+                version: FormalCacheVersion::CURRENT,
+                contents_hash: cache_contents_hash,
+                stdout_stderr,
+                result,
+            }) = fs::read(&cache_file)
+                .ok()
+                .and_then(|v| serde_json::from_slice(&v).ok())
+            {
+                if cache_contents_hash == contents_hash {
+                    println!("Using cached formal result:\n{stdout_stderr}");
+                    return match result {
+                        Ok(FormalCacheOutput {}) => Ok(output),
+                        Err(error) => Err(CliError(eyre::Report::msg(error))),
+                    };
+                }
+            }
+            true
+        } else {
+            false
+        };
+        let _ = fs::remove_file(&cache_file);
+        let status = self.verilog.firrtl.base.run_external_command(
+            acquired_job,
+            cmd,
+            do_cache.then_some(&mut captured_output),
+        )?;
+        let result = if status.success() {
+            Ok(output)
+        } else {
+            Err(CliError(eyre!(
+                "running {} failed: {status}",
+                self.sby.display()
+            )))
+        };
+        fs::write(
+            cache_file,
+            serde_json::to_string_pretty(&FormalCache {
+                version: FormalCacheVersion::CURRENT,
+                contents_hash: contents_hash.unwrap(),
+                stdout_stderr: captured_output,
+                result: match &result {
+                    Ok(FormalOutput { verilog: _ }) => Ok(FormalCacheOutput {}),
+                    Err(error) => Err(error.to_string()),
+                },
+            })
+            .expect("serialization shouldn't ever fail"),
+        )?;
+        result
+    }
+}
+
+impl<Arg> RunPhase<Arg> for FormalArgs
+where
+    VerilogArgs: RunPhase<Arg, Output = VerilogOutput>,
+{
+    type Output = FormalOutput;
+    fn run_with_job(&self, arg: Arg, acquired_job: &mut AcquiredJob) -> Result<Self::Output> {
+        let verilog_output = self.verilog.run_with_job(arg, acquired_job)?;
+        self.run_impl(verilog_output, acquired_job)
    }
 }

@ -221,6 +694,8 @@ enum CliCommand {
    Firrtl(FirrtlArgs),
    /// Generate Verilog
    Verilog(VerilogArgs),
+    /// Run a formal proof
+    Formal(FormalArgs),
 }

 /// a simple CLI
@ -228,7 +703,7 @@ enum CliCommand {
 /// Use like:
 ///
 /// ```no_run
-/// # use fayalite::hdl_module;
+/// # use fayalite::prelude::*;
 /// # #[hdl_module]
 /// # fn my_module() {}
 /// use fayalite::cli;
@ -241,7 +716,7 @@ enum CliCommand {
 /// You can also use it with a larger [`clap`]-based CLI like so:
 ///
 /// ```no_run
-/// # use fayalite::hdl_module;
+/// # use fayalite::prelude::*;
 /// # #[hdl_module]
 /// # fn my_module() {}
 /// use clap::{Subcommand, Parser};
@ -298,13 +773,16 @@ where
    FirrtlArgs: RunPhase<T, Output = FirrtlOutput>,
 {
    type Output = ();
-    fn run(&self, arg: T) -> Result<Self::Output> {
+    fn run_with_job(&self, arg: T, acquired_job: &mut AcquiredJob) -> Result<Self::Output> {
        match &self.subcommand {
            CliCommand::Firrtl(c) => {
-                c.run(arg)?;
+                c.run_with_job(arg, acquired_job)?;
            }
            CliCommand::Verilog(c) => {
-                c.run(arg)?;
+                c.run_with_job(arg, acquired_job)?;
+            }
+            CliCommand::Formal(c) => {
+                c.run_with_job(arg, acquired_job)?;
            }
        }
        Ok(())
--- a/crates/fayalite/src/clock.rs
+++ b/crates/fayalite/src/clock.rs
@ -2,114 +2,78 @@
 // See Notices.txt for copyright information
 use crate::{
    expr::{Expr, ToExpr},
-    int::{UInt, UIntType},
-    intern::Interned,
-    reset::Reset,
+    hdl,
+    int::Bool,
+    reset::{Reset, ResetType},
    source_location::SourceLocation,
-    ty::{
-        impl_match_values_as_self, CanonicalType, CanonicalTypeKind, CanonicalValue, Connect,
-        DynCanonicalType, StaticType, Type, TypeEnum, Value, ValueEnum,
-    },
-    type_deduction::{HitUndeducedType, UndeducedType},
-    util::interned_bit,
+    ty::{impl_match_variant_as_self, CanonicalType, StaticType, Type, TypeProperties},
 };
 use bitvec::slice::BitSlice;

 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
-pub struct ClockType;
+pub struct Clock;

-impl ClockType {
-    pub const fn new() -> Self {
-        Self
-    }
-}
+impl Type for Clock {
+    type BaseType = Clock;
+    type MaskType = Bool;
+    type SimValue = bool;

-impl Connect<UndeducedType> for ClockType {}
-
-impl Type for ClockType {
-    type Value = Clock;
-    type CanonicalType = ClockType;
-    type CanonicalValue = Clock;
-    type MaskType = UIntType<1>;
-    type MaskValue = UInt<1>;
-
-    impl_match_values_as_self!();
+    impl_match_variant_as_self!();

    fn mask_type(&self) -> Self::MaskType {
-        UIntType::new()
+        Bool
    }

-    fn type_enum(&self) -> TypeEnum {
-        TypeEnum::Clock(*self)
+    fn canonical(&self) -> CanonicalType {
+        CanonicalType::Clock(*self)
    }

-    fn from_canonical_type(t: Self::CanonicalType) -> Self {
-        t
-    }
-
-    fn canonical(&self) -> Self::CanonicalType {
-        *self
-    }
-
-    fn source_location(&self) -> SourceLocation {
+    fn source_location() -> SourceLocation {
        SourceLocation::builtin()
    }

-    fn as_dyn_canonical_type_impl(this: &Self) -> Option<&dyn DynCanonicalType> {
-        Some(this)
+    fn from_canonical(canonical_type: CanonicalType) -> Self {
+        let CanonicalType::Clock(retval) = canonical_type else {
+            panic!("expected Clock");
+        };
+        retval
+    }
+
+    fn sim_value_from_bits(&self, bits: &BitSlice) -> Self::SimValue {
+        assert_eq!(bits.len(), 1);
+        bits[0]
+    }
+
+    fn sim_value_clone_from_bits(&self, value: &mut Self::SimValue, bits: &BitSlice) {
+        assert_eq!(bits.len(), 1);
+        *value = bits[0];
+    }
+
+    fn sim_value_to_bits(&self, value: &Self::SimValue, bits: &mut BitSlice) {
+        assert_eq!(bits.len(), 1);
+        bits.set(0, *value);
    }
 }

-impl Connect<Self> for ClockType {}
-
-impl CanonicalType for ClockType {
-    const CANONICAL_TYPE_KIND: CanonicalTypeKind = CanonicalTypeKind::Clock;
-}
-
-impl StaticType for ClockType {
-    fn static_type() -> Self {
-        Self
+impl Clock {
+    pub fn type_properties(self) -> TypeProperties {
+        Self::TYPE_PROPERTIES
+    }
+    pub fn can_connect(self, _rhs: Self) -> bool {
+        true
    }
 }

-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
-pub struct Clock(pub bool);
-
-impl ToExpr for Clock {
-    type Type = ClockType;
-
-    fn ty(&self) -> Self::Type {
-        ClockType
-    }
-
-    fn to_expr(&self) -> Expr<Self> {
-        Expr::from_value(self)
-    }
-}
-
-impl Value for Clock {
-    fn to_canonical(&self) -> <Self::Type as Type>::CanonicalValue {
-        *self
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
-
-impl CanonicalValue for Clock {
-    fn value_enum_impl(this: &Self) -> ValueEnum {
-        ValueEnum::Clock(*this)
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, Value)]
-#[hdl(static, outline_generated)]
-pub struct ClockDomain {
-    pub clk: Clock,
-    pub rst: Reset,
+impl StaticType for Clock {
+    const TYPE: Self = Self;
+    const MASK_TYPE: Self::MaskType = Bool;
+    const TYPE_PROPERTIES: TypeProperties = TypeProperties {
+        is_passive: true,
+        is_storable: false,
+        is_castable_from_bits: true,
+        bit_width: 1,
+    };
+    const MASK_TYPE_PROPERTIES: TypeProperties = Bool::TYPE_PROPERTIES;
 }

 pub trait ToClock {
@ -140,10 +104,10 @@ impl ToClock for Expr<Clock> {
    }
 }

-impl ToClock for Clock {
-    fn to_clock(&self) -> Expr<Clock> {
-        self.to_expr()
-    }
+#[hdl]
+pub struct ClockDomain<R: ResetType = Reset> {
+    pub clk: Clock,
+    pub rst: R,
 }

 impl ToClock for bool {
@ -151,9 +115,3 @@ impl ToClock for bool {
        self.to_expr().to_clock()
    }
 }
-
-impl ToClock for UInt<1> {
-    fn to_clock(&self) -> Expr<Clock> {
-        self.to_expr().to_clock()
-    }
-}
--- a/crates/fayalite/src/enum_.rs
+++ b/crates/fayalite/src/enum_.rs
--- a/crates/fayalite/src/expr.rs
+++ b/crates/fayalite/src/expr.rs
--- a/crates/fayalite/src/expr/ops.rs
+++ b/crates/fayalite/src/expr/ops.rs
--- a/crates/fayalite/src/expr/target.rs
+++ b/crates/fayalite/src/expr/target.rs
@ -0,0 +1,489 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use crate::{
+    array::Array,
+    bundle::{Bundle, BundleField},
+    expr::{Expr, Flow, ToExpr},
+    intern::{Intern, Interned},
+    memory::{DynPortType, MemPort},
+    module::{Instance, ModuleIO, TargetName},
+    reg::Reg,
+    reset::{AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset},
+    source_location::SourceLocation,
+    ty::{CanonicalType, Type},
+    wire::Wire,
+};
+use std::fmt;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TargetPathBundleField {
+    pub name: Interned<str>,
+}
+
+impl fmt::Display for TargetPathBundleField {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, ".{}", self.name)
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TargetPathArrayElement {
+    pub index: usize,
+}
+
+impl fmt::Display for TargetPathArrayElement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "[{}]", self.index)
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TargetPathDynArrayElement {}
+
+impl fmt::Display for TargetPathDynArrayElement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "[<dyn>]")
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum TargetPathElement {
+    BundleField(TargetPathBundleField),
+    ArrayElement(TargetPathArrayElement),
+    DynArrayElement(TargetPathDynArrayElement),
+}
+
+impl From<TargetPathBundleField> for TargetPathElement {
+    fn from(value: TargetPathBundleField) -> Self {
+        Self::BundleField(value)
+    }
+}
+
+impl From<TargetPathArrayElement> for TargetPathElement {
+    fn from(value: TargetPathArrayElement) -> Self {
+        Self::ArrayElement(value)
+    }
+}
+
+impl From<TargetPathDynArrayElement> for TargetPathElement {
+    fn from(value: TargetPathDynArrayElement) -> Self {
+        Self::DynArrayElement(value)
+    }
+}
+
+impl fmt::Display for TargetPathElement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::BundleField(v) => v.fmt(f),
+            Self::ArrayElement(v) => v.fmt(f),
+            Self::DynArrayElement(v) => v.fmt(f),
+        }
+    }
+}
+
+impl TargetPathElement {
+    pub fn canonical_ty(&self, parent: Interned<Target>) -> CanonicalType {
+        match self {
+            &Self::BundleField(TargetPathBundleField { name }) => {
+                let parent_ty = Bundle::from_canonical(parent.canonical_ty());
+                let field = parent_ty
+                    .field_by_name(name)
+                    .expect("field name is known to be a valid field of parent type");
+                field.ty
+            }
+            &Self::ArrayElement(TargetPathArrayElement { index }) => {
+                let parent_ty = Array::<CanonicalType>::from_canonical(parent.canonical_ty());
+                assert!(index < parent_ty.len());
+                parent_ty.element()
+            }
+            Self::DynArrayElement(_) => {
+                let parent_ty = Array::<CanonicalType>::from_canonical(parent.canonical_ty());
+                parent_ty.element()
+            }
+        }
+    }
+    pub fn flow(&self, parent: Interned<Target>) -> Flow {
+        match self {
+            Self::BundleField(v) => {
+                let parent_ty = Bundle::from_canonical(parent.canonical_ty());
+                let field = parent_ty
+                    .field_by_name(v.name)
+                    .expect("field name is known to be a valid field of parent type");
+                parent.flow().flip_if(field.flipped)
+            }
+            Self::ArrayElement(_) => parent.flow(),
+            Self::DynArrayElement(_) => parent.flow(),
+        }
+    }
+    pub fn is_static(&self) -> bool {
+        match self {
+            Self::BundleField(_) | Self::ArrayElement(_) => true,
+            Self::DynArrayElement(_) => false,
+        }
+    }
+}
+
+macro_rules! impl_target_base {
+    (
+        $(#[$enum_meta:meta])*
+        $enum_vis:vis enum $TargetBase:ident {
+            $(
+                $(#[from = $from:ident])?
+                #[is = $is_fn:ident]
+                #[to = $to_fn:ident]
+                $(#[$variant_meta:meta])*
+                $Variant:ident($VariantTy:ty),
+            )*
+        }
+    ) => {
+        $(#[$enum_meta])*
+        $enum_vis enum $TargetBase {
+            $(
+                $(#[$variant_meta])*
+                $Variant($VariantTy),
+            )*
+        }
+
+        impl fmt::Debug for $TargetBase {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                match self {
+                    $(Self::$Variant(v) => v.fmt(f),)*
+                }
+            }
+        }
+
+        $($(
+        impl From<$VariantTy> for $TargetBase {
+            fn $from(value: $VariantTy) -> Self {
+                Self::$Variant(value)
+            }
+        }
+
+        impl From<$VariantTy> for Target {
+            fn $from(value: $VariantTy) -> Self {
+                $TargetBase::$Variant(value).into()
+            }
+        }
+        )*)?
+
+        impl $TargetBase {
+            $(
+            $enum_vis fn $is_fn(&self) -> bool {
+                self.$to_fn().is_some()
+            }
+            $enum_vis fn $to_fn(&self) -> Option<&$VariantTy> {
+                if let Self::$Variant(retval) = self {
+                    Some(retval)
+                } else {
+                    None
+                }
+            }
+            )*
+            $enum_vis fn must_connect_to(&self) -> bool {
+                match self {
+                    $(Self::$Variant(v) => v.must_connect_to(),)*
+                }
+            }
+            $enum_vis fn flow(&self) -> Flow {
+                match self {
+                    $(Self::$Variant(v) => v.flow(),)*
+                }
+            }
+            $enum_vis fn source_location(&self) -> SourceLocation {
+                match self {
+                    $(Self::$Variant(v) => v.source_location(),)*
+                }
+            }
+        }
+
+        impl ToExpr for $TargetBase {
+            type Type = CanonicalType;
+
+            fn to_expr(&self) -> Expr<Self::Type> {
+                match self {
+                    $(Self::$Variant(v) => Expr::canonical(v.to_expr()),)*
+                }
+            }
+        }
+    };
+}
+
+impl_target_base! {
+    #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+    pub enum TargetBase {
+        #[from = from]
+        #[is = is_module_io]
+        #[to = module_io]
+        ModuleIO(ModuleIO<CanonicalType>),
+        #[from = from]
+        #[is = is_mem_port]
+        #[to = mem_port]
+        MemPort(MemPort<DynPortType>),
+        #[is = is_reg]
+        #[to = reg]
+        Reg(Reg<CanonicalType, Reset>),
+        #[is = is_reg_sync]
+        #[to = reg_sync]
+        RegSync(Reg<CanonicalType, SyncReset>),
+        #[is = is_reg_async]
+        #[to = reg_async]
+        RegAsync(Reg<CanonicalType, AsyncReset>),
+        #[from = from]
+        #[is = is_wire]
+        #[to = wire]
+        Wire(Wire<CanonicalType>),
+        #[from = from]
+        #[is = is_instance]
+        #[to = instance]
+        Instance(Instance<Bundle>),
+    }
+}
+
+impl<R: ResetType> From<Reg<CanonicalType, R>> for TargetBase {
+    fn from(value: Reg<CanonicalType, R>) -> Self {
+        struct Dispatch;
+        impl ResetTypeDispatch for Dispatch {
+            type Input<T: ResetType> = Reg<CanonicalType, T>;
+            type Output<T: ResetType> = TargetBase;
+
+            fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset> {
+                TargetBase::Reg(input)
+            }
+
+            fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset> {
+                TargetBase::RegSync(input)
+            }
+
+            fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset> {
+                TargetBase::RegAsync(input)
+            }
+        }
+        R::dispatch(value, Dispatch)
+    }
+}
+
+impl<R: ResetType> From<Reg<CanonicalType, R>> for Target {
+    fn from(value: Reg<CanonicalType, R>) -> Self {
+        TargetBase::from(value).into()
+    }
+}
+
+impl fmt::Display for TargetBase {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self.target_name())
+    }
+}
+
+impl TargetBase {
+    pub fn target_name(&self) -> TargetName {
+        match self {
+            TargetBase::ModuleIO(v) => TargetName(v.scoped_name(), None),
+            TargetBase::MemPort(v) => TargetName(v.mem_name(), Some(v.port_name())),
+            TargetBase::Reg(v) => TargetName(v.scoped_name(), None),
+            TargetBase::RegSync(v) => TargetName(v.scoped_name(), None),
+            TargetBase::RegAsync(v) => TargetName(v.scoped_name(), None),
+            TargetBase::Wire(v) => TargetName(v.scoped_name(), None),
+            TargetBase::Instance(v) => TargetName(v.scoped_name(), None),
+        }
+    }
+    pub fn canonical_ty(&self) -> CanonicalType {
+        match self {
+            TargetBase::ModuleIO(v) => v.ty(),
+            TargetBase::MemPort(v) => v.ty().canonical(),
+            TargetBase::Reg(v) => v.ty(),
+            TargetBase::RegSync(v) => v.ty(),
+            TargetBase::RegAsync(v) => v.ty(),
+            TargetBase::Wire(v) => v.ty(),
+            TargetBase::Instance(v) => v.ty().canonical(),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TargetChild {
+    parent: Interned<Target>,
+    path_element: Interned<TargetPathElement>,
+    canonical_ty: CanonicalType,
+    flow: Flow,
+}
+
+impl fmt::Debug for TargetChild {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self {
+            parent,
+            path_element,
+            canonical_ty: _,
+            flow: _,
+        } = self;
+        parent.fmt(f)?;
+        fmt::Display::fmt(path_element, f)
+    }
+}
+
+impl fmt::Display for TargetChild {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self {
+            parent,
+            path_element,
+            canonical_ty: _,
+            flow: _,
+        } = self;
+        parent.fmt(f)?;
+        path_element.fmt(f)
+    }
+}
+
+impl TargetChild {
+    pub fn new(parent: Interned<Target>, path_element: Interned<TargetPathElement>) -> Self {
+        Self {
+            parent,
+            path_element,
+            canonical_ty: path_element.canonical_ty(parent),
+            flow: path_element.flow(parent),
+        }
+    }
+    pub fn parent(self) -> Interned<Target> {
+        self.parent
+    }
+    pub fn path_element(self) -> Interned<TargetPathElement> {
+        self.path_element
+    }
+    pub fn canonical_ty(self) -> CanonicalType {
+        self.canonical_ty
+    }
+    pub fn flow(self) -> Flow {
+        self.flow
+    }
+    pub fn bundle_field(self) -> Option<BundleField> {
+        if let TargetPathElement::BundleField(TargetPathBundleField { name }) = *self.path_element {
+            let parent_ty = Bundle::from_canonical(self.parent.canonical_ty());
+            Some(
+                parent_ty
+                    .field_by_name(name)
+                    .expect("field name known to be a valid field of parent"),
+            )
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Target {
+    Base(Interned<TargetBase>),
+    Child(TargetChild),
+}
+
+impl From<TargetBase> for Target {
+    fn from(value: TargetBase) -> Self {
+        Self::Base(Intern::intern_sized(value))
+    }
+}
+
+impl From<TargetChild> for Target {
+    fn from(value: TargetChild) -> Self {
+        Self::Child(value)
+    }
+}
+
+impl From<Interned<TargetBase>> for Target {
+    fn from(value: Interned<TargetBase>) -> Self {
+        Self::Base(value)
+    }
+}
+
+impl Target {
+    pub fn base(&self) -> Interned<TargetBase> {
+        let mut target = self;
+        loop {
+            match target {
+                Self::Base(v) => break *v,
+                Self::Child(v) => target = &v.parent,
+            }
+        }
+    }
+    pub fn child(&self) -> Option<TargetChild> {
+        match *self {
+            Target::Base(_) => None,
+            Target::Child(v) => Some(v),
+        }
+    }
+    pub fn is_static(&self) -> bool {
+        let mut target = self;
+        loop {
+            match target {
+                Self::Base(_) => return true,
+                Self::Child(v) if !v.path_element().is_static() => return false,
+                Self::Child(v) => target = &v.parent,
+            }
+        }
+    }
+    #[must_use]
+    pub fn join(&self, path_element: Interned<TargetPathElement>) -> Self {
+        TargetChild::new(self.intern(), path_element).into()
+    }
+    pub fn flow(&self) -> Flow {
+        match self {
+            Self::Base(v) => v.flow(),
+            Self::Child(v) => v.flow(),
+        }
+    }
+    pub fn canonical_ty(&self) -> CanonicalType {
+        match self {
+            Target::Base(v) => v.canonical_ty(),
+            Target::Child(v) => v.canonical_ty(),
+        }
+    }
+}
+
+impl fmt::Display for Target {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Base(v) => v.fmt(f),
+            Self::Child(v) => v.fmt(f),
+        }
+    }
+}
+
+impl fmt::Debug for Target {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Base(v) => v.fmt(f),
+            Self::Child(v) => v.fmt(f),
+        }
+    }
+}
+
+pub trait GetTarget {
+    fn target(&self) -> Option<Interned<Target>>;
+}
+
+impl GetTarget for bool {
+    fn target(&self) -> Option<Interned<Target>> {
+        None
+    }
+}
+
+impl<T: ?Sized + GetTarget + Send + Sync + 'static> GetTarget for Interned<T> {
+    fn target(&self) -> Option<Interned<Target>> {
+        T::target(self)
+    }
+}
+
+impl<T: ?Sized + GetTarget> GetTarget for &'_ T {
+    fn target(&self) -> Option<Interned<Target>> {
+        T::target(self)
+    }
+}
+
+impl<T: ?Sized + GetTarget> GetTarget for &'_ mut T {
+    fn target(&self) -> Option<Interned<Target>> {
+        T::target(self)
+    }
+}
+
+impl<T: ?Sized + GetTarget> GetTarget for Box<T> {
+    fn target(&self) -> Option<Interned<Target>> {
+        T::target(self)
+    }
+}
--- a/crates/fayalite/src/firrtl.rs
+++ b/crates/fayalite/src/firrtl.rs
--- a/crates/fayalite/src/formal.rs
+++ b/crates/fayalite/src/formal.rs
@ -0,0 +1,247 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use crate::{
+    int::BoolOrIntType,
+    intern::{Intern, Interned, Memoize},
+    prelude::*,
+};
+use std::sync::OnceLock;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum FormalKind {
+    Assert,
+    Assume,
+    Cover,
+}
+
+impl FormalKind {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Assert => "assert",
+            Self::Assume => "assume",
+            Self::Cover => "cover",
+        }
+    }
+}
+
+#[track_caller]
+pub fn formal_stmt_with_enable_and_loc(
+    kind: FormalKind,
+    clk: Expr<Clock>,
+    pred: Expr<Bool>,
+    en: Expr<Bool>,
+    text: &str,
+    source_location: SourceLocation,
+) {
+    crate::module::add_stmt_formal(crate::module::StmtFormal {
+        kind,
+        clk,
+        pred,
+        en: en & !formal_reset().cast_to_static::<Bool>(),
+        text: text.intern(),
+        source_location,
+    });
+}
+
+#[track_caller]
+pub fn formal_stmt_with_enable(
+    kind: FormalKind,
+    clk: Expr<Clock>,
+    pred: Expr<Bool>,
+    en: Expr<Bool>,
+    text: &str,
+) {
+    formal_stmt_with_enable_and_loc(kind, clk, pred, en, text, SourceLocation::caller());
+}
+
+#[track_caller]
+pub fn formal_stmt_with_loc(
+    kind: FormalKind,
+    clk: Expr<Clock>,
+    pred: Expr<Bool>,
+    text: &str,
+    source_location: SourceLocation,
+) {
+    formal_stmt_with_enable_and_loc(kind, clk, pred, true.to_expr(), text, source_location);
+}
+
+#[track_caller]
+pub fn formal_stmt(kind: FormalKind, clk: Expr<Clock>, pred: Expr<Bool>, text: &str) {
+    formal_stmt_with_loc(kind, clk, pred, text, SourceLocation::caller());
+}
+
+macro_rules! make_formal {
+    ($kind:ident, $formal_stmt_with_enable_and_loc:ident, $formal_stmt_with_enable:ident, $formal_stmt_with_loc:ident, $formal_stmt:ident) => {
+        #[track_caller]
+        pub fn $formal_stmt_with_enable_and_loc(
+            clk: Expr<Clock>,
+            pred: Expr<Bool>,
+            en: Expr<Bool>,
+            text: &str,
+            source_location: SourceLocation,
+        ) {
+            formal_stmt_with_enable_and_loc(
+                FormalKind::$kind,
+                clk,
+                pred,
+                en,
+                text,
+                source_location,
+            );
+        }
+        #[track_caller]
+        pub fn $formal_stmt_with_enable(
+            clk: Expr<Clock>,
+            pred: Expr<Bool>,
+            en: Expr<Bool>,
+            text: &str,
+        ) {
+            formal_stmt_with_enable(FormalKind::$kind, clk, pred, en, text);
+        }
+        #[track_caller]
+        pub fn $formal_stmt_with_loc(
+            clk: Expr<Clock>,
+            pred: Expr<Bool>,
+            text: &str,
+            source_location: SourceLocation,
+        ) {
+            formal_stmt_with_loc(FormalKind::$kind, clk, pred, text, source_location);
+        }
+        #[track_caller]
+        pub fn $formal_stmt(clk: Expr<Clock>, pred: Expr<Bool>, text: &str) {
+            formal_stmt(FormalKind::$kind, clk, pred, text);
+        }
+    };
+}
+
+make_formal!(
+    Assert,
+    hdl_assert_with_enable_and_loc,
+    hdl_assert_with_enable,
+    hdl_assert_with_loc,
+    hdl_assert
+);
+
+make_formal!(
+    Assume,
+    hdl_assume_with_enable_and_loc,
+    hdl_assume_with_enable,
+    hdl_assume_with_loc,
+    hdl_assume
+);
+
+make_formal!(
+    Cover,
+    hdl_cover_with_enable_and_loc,
+    hdl_cover_with_enable,
+    hdl_cover_with_loc,
+    hdl_cover
+);
+
+pub trait MakeFormalExpr: Type {}
+
+impl<T: Type> MakeFormalExpr for T {}
+
+#[hdl]
+pub fn formal_global_clock() -> Expr<Clock> {
+    #[hdl_module(extern)]
+    fn formal_global_clock() {
+        #[hdl]
+        let clk: Clock = m.output();
+        m.annotate_module(BlackBoxInlineAnnotation {
+            path: "fayalite_formal_global_clock.v".intern(),
+            text: r"module __fayalite_formal_global_clock(output clk);
+    (* gclk *)
+    reg clk;
+endmodule
+"
+            .intern(),
+        });
+        m.verilog_name("__fayalite_formal_global_clock");
+    }
+    #[hdl]
+    let formal_global_clock = instance(formal_global_clock());
+    formal_global_clock.clk
+}
+
+#[hdl]
+pub fn formal_reset() -> Expr<SyncReset> {
+    #[hdl_module(extern)]
+    fn formal_reset() {
+        #[hdl]
+        let rst: SyncReset = m.output();
+        m.annotate_module(BlackBoxInlineAnnotation {
+            path: "fayalite_formal_reset.v".intern(),
+            text: r"module __fayalite_formal_reset(output rst);
+    assign rst = $initstate;
+endmodule
+"
+            .intern(),
+        });
+        m.verilog_name("__fayalite_formal_reset");
+    }
+    static MOD: OnceLock<Interned<Module<formal_reset>>> = OnceLock::new();
+    #[hdl]
+    let formal_reset = instance(*MOD.get_or_init(formal_reset));
+    formal_reset.rst
+}
+
+macro_rules! make_any_const_fn {
+    ($ident:ident, $verilog_attribute:literal) => {
+        #[hdl]
+        pub fn $ident<T: BoolOrIntType>(ty: T) -> Expr<T> {
+            #[hdl_module(extern)]
+            pub(super) fn $ident<T: BoolOrIntType>(ty: T) {
+                #[hdl]
+                let out: T = m.output(ty);
+                let width = ty.width();
+                let verilog_bitslice = if width == 1 {
+                    String::new()
+                } else {
+                    format!(" [{}:0]", width - 1)
+                };
+                m.annotate_module(BlackBoxInlineAnnotation {
+                    path: Intern::intern_owned(format!(
+                        "fayalite_{}_{width}.v",
+                        stringify!($ident),
+                    )),
+                    text: Intern::intern_owned(format!(
+                        r"module __fayalite_{}_{width}(output{verilog_bitslice} out);
+    (* {} *)
+    reg{verilog_bitslice} out;
+endmodule
+",
+                        stringify!($ident),
+                        $verilog_attribute,
+                    )),
+                });
+                m.verilog_name(format!("__fayalite_{}_{width}", stringify!($ident)));
+            }
+            #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+            struct TheMemoize<T>(T);
+            impl<T: BoolOrIntType> Memoize for TheMemoize<T> {
+                type Input = ();
+                type InputOwned = ();
+                type Output = Option<Interned<Module<$ident<T>>>>;
+                fn inner(self, _input: &Self::Input) -> Self::Output {
+                    if self.0.width() == 0 {
+                        None
+                    } else {
+                        Some($ident(self.0))
+                    }
+                }
+            }
+            let Some(module) = TheMemoize(ty).get_owned(()) else {
+                return 0_hdl_u0.cast_bits_to(ty);
+            };
+            #[hdl]
+            let $ident = instance(module);
+            $ident.out
+        }
+    };
+}
+
+make_any_const_fn!(any_const, "anyconst");
+make_any_const_fn!(any_seq, "anyseq");
+make_any_const_fn!(all_const, "allconst");
+make_any_const_fn!(all_seq, "allseq");
--- a/crates/fayalite/src/int.rs
+++ b/crates/fayalite/src/int.rs
--- a/crates/fayalite/src/int/uint_in_range.rs
+++ b/crates/fayalite/src/int/uint_in_range.rs
@ -0,0 +1,614 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    bundle::{Bundle, BundleField, BundleType, BundleTypePropertiesBuilder, NoBuilder},
+    expr::{
+        ops::{ExprCastTo, ExprPartialEq, ExprPartialOrd},
+        CastBitsTo, CastTo, CastToBits, Expr, HdlPartialEq, HdlPartialOrd,
+    },
+    int::{Bool, DynSize, KnownSize, Size, SizeType, UInt, UIntType},
+    intern::{Intern, Interned},
+    phantom_const::PhantomConst,
+    sim::value::{SimValue, SimValuePartialEq, ToSimValueWithType},
+    source_location::SourceLocation,
+    ty::{impl_match_variant_as_self, CanonicalType, StaticType, Type, TypeProperties},
+};
+use bitvec::{order::Lsb0, slice::BitSlice, view::BitView};
+use serde::{
+    de::{value::UsizeDeserializer, Error, Visitor},
+    Deserialize, Deserializer, Serialize, Serializer,
+};
+use std::{fmt, marker::PhantomData, ops::Index};
+
+const UINT_IN_RANGE_TYPE_FIELD_NAMES: [&'static str; 2] = ["value", "range"];
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+pub struct UIntInRangeMaskType {
+    value: Bool,
+    range: PhantomConstRangeMaskType,
+}
+
+impl Type for UIntInRangeMaskType {
+    type BaseType = Bundle;
+    type MaskType = Self;
+    type SimValue = bool;
+    impl_match_variant_as_self!();
+
+    fn mask_type(&self) -> Self::MaskType {
+        *self
+    }
+
+    fn canonical(&self) -> CanonicalType {
+        CanonicalType::Bundle(Bundle::new(self.fields()))
+    }
+
+    fn from_canonical(canonical_type: CanonicalType) -> Self {
+        let fields = Bundle::from_canonical(canonical_type).fields();
+        let [BundleField {
+            name: value_name,
+            flipped: false,
+            ty: value,
+        }, BundleField {
+            name: range_name,
+            flipped: false,
+            ty: range,
+        }] = *fields
+        else {
+            panic!("expected UIntInRangeMaskType");
+        };
+        assert_eq!([&*value_name, &*range_name], UINT_IN_RANGE_TYPE_FIELD_NAMES);
+        let value = Bool::from_canonical(value);
+        let range = PhantomConstRangeMaskType::from_canonical(range);
+        Self { value, range }
+    }
+
+    fn source_location() -> SourceLocation {
+        SourceLocation::builtin()
+    }
+
+    fn sim_value_from_bits(&self, bits: &BitSlice) -> Self::SimValue {
+        Bool.sim_value_from_bits(bits)
+    }
+
+    fn sim_value_clone_from_bits(&self, value: &mut Self::SimValue, bits: &BitSlice) {
+        Bool.sim_value_clone_from_bits(value, bits);
+    }
+
+    fn sim_value_to_bits(&self, value: &Self::SimValue, bits: &mut BitSlice) {
+        Bool.sim_value_to_bits(value, bits);
+    }
+}
+
+impl BundleType for UIntInRangeMaskType {
+    type Builder = NoBuilder;
+    type FilledBuilder = Expr<UIntInRangeMaskType>;
+
+    fn fields(&self) -> Interned<[BundleField]> {
+        let [value_name, range_name] = UINT_IN_RANGE_TYPE_FIELD_NAMES;
+        let Self { value, range } = self;
+        [
+            BundleField {
+                name: value_name.intern(),
+                flipped: false,
+                ty: value.canonical(),
+            },
+            BundleField {
+                name: range_name.intern(),
+                flipped: false,
+                ty: range.canonical(),
+            },
+        ][..]
+            .intern()
+    }
+}
+
+impl StaticType for UIntInRangeMaskType {
+    const TYPE: Self = Self {
+        value: Bool,
+        range: PhantomConstRangeMaskType::TYPE,
+    };
+    const MASK_TYPE: Self::MaskType = Self::TYPE;
+    const TYPE_PROPERTIES: TypeProperties = BundleTypePropertiesBuilder::new()
+        .field(false, Bool::TYPE_PROPERTIES)
+        .field(false, PhantomConstRangeMaskType::TYPE_PROPERTIES)
+        .finish();
+    const MASK_TYPE_PROPERTIES: TypeProperties = Self::TYPE_PROPERTIES;
+}
+
+impl ToSimValueWithType<UIntInRangeMaskType> for bool {
+    fn to_sim_value_with_type(&self, ty: UIntInRangeMaskType) -> SimValue<UIntInRangeMaskType> {
+        SimValue::from_value(ty, *self)
+    }
+}
+
+impl ExprCastTo<Bool> for UIntInRangeMaskType {
+    fn cast_to(src: Expr<Self>, to_type: Bool) -> Expr<Bool> {
+        src.cast_to_bits().cast_to(to_type)
+    }
+}
+
+impl ExprCastTo<UIntInRangeMaskType> for Bool {
+    fn cast_to(src: Expr<Self>, to_type: UIntInRangeMaskType) -> Expr<UIntInRangeMaskType> {
+        src.cast_to_static::<UInt<1>>().cast_bits_to(to_type)
+    }
+}
+
+impl ExprPartialEq<Self> for UIntInRangeMaskType {
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        lhs.cast_to_bits().cmp_eq(rhs.cast_to_bits())
+    }
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        lhs.cast_to_bits().cmp_ne(rhs.cast_to_bits())
+    }
+}
+
+impl SimValuePartialEq<Self> for UIntInRangeMaskType {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        **this == **other
+    }
+}
+
+type PhantomConstRangeMaskType = <PhantomConst<SerdeRange<DynSize, DynSize>> as Type>::MaskType;
+
+#[derive(Default, Copy, Clone, Debug)]
+struct RangeParseError;
+
+macro_rules! define_uint_in_range_type {
+    (
+        $UIntInRange:ident,
+        $UIntInRangeType:ident,
+        $UIntInRangeTypeWithoutGenerics:ident,
+        $UIntInRangeTypeWithStart:ident,
+        $SerdeRange:ident,
+        $range_operator_str:literal,
+        |$uint_range_usize_start:ident, $uint_range_usize_end:ident| $uint_range_usize:expr,
+    ) => {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct $SerdeRange<Start: Size, End: Size> {
+            start: Start::SizeType,
+            end: End::SizeType,
+        }
+
+        impl<Start: KnownSize, End: KnownSize> Default for $SerdeRange<Start, End> {
+            fn default() -> Self {
+                Self {
+                    start: Start::SIZE,
+                    end: End::SIZE,
+                }
+            }
+        }
+
+        impl std::str::FromStr for $SerdeRange<DynSize, DynSize> {
+            type Err = RangeParseError;
+
+            fn from_str(s: &str) -> Result<Self, Self::Err> {
+                let Some((start, end)) = s.split_once($range_operator_str) else {
+                    return Err(RangeParseError);
+                };
+                if start.is_empty()
+                    || start.bytes().any(|b| !b.is_ascii_digit())
+                    || end.is_empty()
+                    || end.bytes().any(|b| !b.is_ascii_digit())
+                {
+                    return Err(RangeParseError);
+                }
+                let start = start.parse().map_err(|_| RangeParseError)?;
+                let end = end.parse().map_err(|_| RangeParseError)?;
+                let retval = Self { start, end };
+                if retval.is_empty() {
+                    Err(RangeParseError)
+                } else {
+                    Ok(retval)
+                }
+            }
+        }
+
+        impl<Start: Size, End: Size> fmt::Display for $SerdeRange<Start, End> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let Self { start, end } = *self;
+                write!(
+                    f,
+                    "{}{}{}",
+                    Start::as_usize(start),
+                    $range_operator_str,
+                    End::as_usize(end),
+                )
+            }
+        }
+
+        impl<Start: Size, End: Size> Serialize for $SerdeRange<Start, End> {
+            fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+                serializer.collect_str(self)
+            }
+        }
+
+        impl<'de, Start: Size, End: Size> Deserialize<'de> for $SerdeRange<Start, End> {
+            fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+                struct SerdeRangeVisitor<Start: Size, End: Size>(PhantomData<(Start, End)>);
+                impl<'de, Start: Size, End: Size> Visitor<'de> for SerdeRangeVisitor<Start, End> {
+                    type Value = $SerdeRange<Start, End>;
+
+                    fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                        f.write_str("a string with format \"")?;
+                        if let Some(start) = Start::KNOWN_VALUE {
+                            write!(f, "{start}")?;
+                        } else {
+                            f.write_str("<int>")?;
+                        };
+                        f.write_str($range_operator_str)?;
+                        if let Some(end) = End::KNOWN_VALUE {
+                            write!(f, "{end}")?;
+                        } else {
+                            f.write_str("<int>")?;
+                        };
+                        f.write_str("\" that is a non-empty range")
+                    }
+
+                    fn visit_str<E: Error>(self, v: &str) -> Result<Self::Value, E> {
+                        let $SerdeRange::<DynSize, DynSize> { start, end } =
+                            v.parse().map_err(|_| {
+                                Error::invalid_value(serde::de::Unexpected::Str(v), &self)
+                            })?;
+                        let start =
+                            Start::SizeType::deserialize(UsizeDeserializer::<E>::new(start))?;
+                        let end = End::SizeType::deserialize(UsizeDeserializer::<E>::new(end))?;
+                        Ok($SerdeRange { start, end })
+                    }
+
+                    fn visit_bytes<E: Error>(self, v: &[u8]) -> Result<Self::Value, E> {
+                        match std::str::from_utf8(v) {
+                            Ok(v) => self.visit_str(v),
+                            Err(_) => {
+                                Err(Error::invalid_value(serde::de::Unexpected::Bytes(v), &self))
+                            }
+                        }
+                    }
+                }
+                deserializer.deserialize_str(SerdeRangeVisitor(PhantomData))
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        pub struct $UIntInRangeType<Start: Size, End: Size> {
+            value: UInt,
+            range: PhantomConst<$SerdeRange<Start, End>>,
+        }
+
+        impl<Start: Size, End: Size> $UIntInRangeType<Start, End> {
+            fn from_phantom_const_range(range: PhantomConst<$SerdeRange<Start, End>>) -> Self {
+                let $SerdeRange { start, end } = *range.get();
+                let $uint_range_usize_start = Start::as_usize(start);
+                let $uint_range_usize_end = End::as_usize(end);
+                Self {
+                    value: $uint_range_usize,
+                    range,
+                }
+            }
+            pub fn new(start: Start::SizeType, end: End::SizeType) -> Self {
+                Self::from_phantom_const_range(PhantomConst::new(
+                    $SerdeRange { start, end }.intern_sized(),
+                ))
+            }
+        }
+
+        impl<Start: Size, End: Size> fmt::Debug for $UIntInRangeType<Start, End> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let Self { value, range } = self;
+                let $SerdeRange { start, end } = *range.get();
+                f.debug_struct(&format!(
+                    "{}<{}, {}>",
+                    stringify!($UIntInRange),
+                    Start::as_usize(start),
+                    End::as_usize(end),
+                ))
+                .field("value", value)
+                .finish_non_exhaustive()
+            }
+        }
+
+        impl<Start: Size, End: Size> Type for $UIntInRangeType<Start, End> {
+            type BaseType = Bundle;
+            type MaskType = UIntInRangeMaskType;
+            type SimValue = usize;
+            impl_match_variant_as_self!();
+
+            fn mask_type(&self) -> Self::MaskType {
+                UIntInRangeMaskType::TYPE
+            }
+
+            fn canonical(&self) -> CanonicalType {
+                CanonicalType::Bundle(Bundle::new(self.fields()))
+            }
+
+            fn from_canonical(canonical_type: CanonicalType) -> Self {
+                let fields = Bundle::from_canonical(canonical_type).fields();
+                let [BundleField {
+                    name: value_name,
+                    flipped: false,
+                    ty: value,
+                }, BundleField {
+                    name: range_name,
+                    flipped: false,
+                    ty: range,
+                }] = *fields
+                else {
+                    panic!("expected {}", stringify!($UIntInRange));
+                };
+                assert_eq!([&*value_name, &*range_name], UINT_IN_RANGE_TYPE_FIELD_NAMES);
+                let value = UInt::from_canonical(value);
+                let range = PhantomConst::<$SerdeRange<Start, End>>::from_canonical(range);
+                let retval = Self::from_phantom_const_range(range);
+                assert_eq!(retval, Self { value, range });
+                retval
+            }
+
+            fn source_location() -> SourceLocation {
+                SourceLocation::builtin()
+            }
+
+            fn sim_value_from_bits(&self, bits: &BitSlice) -> Self::SimValue {
+                let mut retval = 0usize;
+                retval.view_bits_mut::<Lsb0>()[..bits.len()].clone_from_bitslice(bits);
+                retval
+            }
+
+            fn sim_value_clone_from_bits(&self, value: &mut Self::SimValue, bits: &BitSlice) {
+                *value = self.sim_value_from_bits(bits);
+            }
+
+            fn sim_value_to_bits(&self, value: &Self::SimValue, bits: &mut BitSlice) {
+                bits.clone_from_bitslice(&value.view_bits::<Lsb0>()[..bits.len()]);
+            }
+        }
+
+        impl<Start: Size, End: Size> BundleType for $UIntInRangeType<Start, End> {
+            type Builder = NoBuilder;
+            type FilledBuilder = Expr<Self>;
+
+            fn fields(&self) -> Interned<[BundleField]> {
+                let [value_name, range_name] = UINT_IN_RANGE_TYPE_FIELD_NAMES;
+                let Self { value, range } = self;
+                [
+                    BundleField {
+                        name: value_name.intern(),
+                        flipped: false,
+                        ty: value.canonical(),
+                    },
+                    BundleField {
+                        name: range_name.intern(),
+                        flipped: false,
+                        ty: range.canonical(),
+                    },
+                ][..]
+                    .intern()
+            }
+        }
+
+        impl<Start: KnownSize, End: KnownSize> Default for $UIntInRangeType<Start, End> {
+            fn default() -> Self {
+                Self::TYPE
+            }
+        }
+
+        impl<Start: KnownSize, End: KnownSize> StaticType for $UIntInRangeType<Start, End> {
+            const TYPE: Self = {
+                let $uint_range_usize_start = Start::VALUE;
+                let $uint_range_usize_end = End::VALUE;
+                Self {
+                    value: $uint_range_usize,
+                    range: PhantomConst::<$SerdeRange<Start, End>>::TYPE,
+                }
+            };
+            const MASK_TYPE: Self::MaskType = UIntInRangeMaskType::TYPE;
+            const TYPE_PROPERTIES: TypeProperties = BundleTypePropertiesBuilder::new()
+                .field(false, Self::TYPE.value.type_properties_dyn())
+                .field(
+                    false,
+                    PhantomConst::<$SerdeRange<Start, End>>::TYPE_PROPERTIES,
+                )
+                .finish();
+            const MASK_TYPE_PROPERTIES: TypeProperties = UIntInRangeMaskType::TYPE_PROPERTIES;
+        }
+
+        impl<Start: Size, End: Size> ToSimValueWithType<$UIntInRangeType<Start, End>> for usize {
+            fn to_sim_value_with_type(
+                &self,
+                ty: $UIntInRangeType<Start, End>,
+            ) -> SimValue<$UIntInRangeType<Start, End>> {
+                SimValue::from_value(ty, *self)
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+        pub struct $UIntInRangeTypeWithoutGenerics;
+
+        #[allow(non_upper_case_globals)]
+        pub const $UIntInRangeType: $UIntInRangeTypeWithoutGenerics =
+            $UIntInRangeTypeWithoutGenerics;
+
+        impl<StartSize: SizeType> Index<StartSize> for $UIntInRangeTypeWithoutGenerics {
+            type Output = $UIntInRangeTypeWithStart<StartSize::Size>;
+
+            fn index(&self, start: StartSize) -> &Self::Output {
+                Interned::into_inner($UIntInRangeTypeWithStart(start).intern_sized())
+            }
+        }
+
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        pub struct $UIntInRangeTypeWithStart<Start: Size>(Start::SizeType);
+
+        impl<Start: Size, EndSize: SizeType<Size = End>, End: Size<SizeType = EndSize>>
+            Index<EndSize> for $UIntInRangeTypeWithStart<Start>
+        {
+            type Output = $UIntInRangeType<Start, End>;
+
+            fn index(&self, end: EndSize) -> &Self::Output {
+                Interned::into_inner($UIntInRangeType::new(self.0, end).intern_sized())
+            }
+        }
+
+        impl<Start: Size, End: Size> ExprCastTo<UInt> for $UIntInRangeType<Start, End> {
+            fn cast_to(src: Expr<Self>, to_type: UInt) -> Expr<UInt> {
+                src.cast_to_bits().cast_to(to_type)
+            }
+        }
+
+        impl<Start: Size, End: Size> ExprCastTo<$UIntInRangeType<Start, End>> for UInt {
+            fn cast_to(
+                src: Expr<Self>,
+                to_type: $UIntInRangeType<Start, End>,
+            ) -> Expr<$UIntInRangeType<Start, End>> {
+                src.cast_bits_to(to_type)
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            ExprPartialEq<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn cmp_eq(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_eq(rhs.cast_to_bits())
+            }
+            fn cmp_ne(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ne(rhs.cast_to_bits())
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            ExprPartialOrd<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn cmp_lt(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_lt(rhs.cast_to_bits())
+            }
+            fn cmp_le(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_le(rhs.cast_to_bits())
+            }
+            fn cmp_gt(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_gt(rhs.cast_to_bits())
+            }
+            fn cmp_ge(
+                lhs: Expr<Self>,
+                rhs: Expr<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ge(rhs.cast_to_bits())
+            }
+        }
+
+        impl<LhsStart: Size, LhsEnd: Size, RhsStart: Size, RhsEnd: Size>
+            SimValuePartialEq<$UIntInRangeType<RhsStart, RhsEnd>>
+            for $UIntInRangeType<LhsStart, LhsEnd>
+        {
+            fn sim_value_eq(
+                this: &SimValue<Self>,
+                other: &SimValue<$UIntInRangeType<RhsStart, RhsEnd>>,
+            ) -> bool {
+                **this == **other
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialEq<UIntType<Width>>
+            for $UIntInRangeType<Start, End>
+        {
+            fn cmp_eq(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_eq(rhs)
+            }
+            fn cmp_ne(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ne(rhs)
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialEq<$UIntInRangeType<Start, End>>
+            for UIntType<Width>
+        {
+            fn cmp_eq(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_eq(rhs.cast_to_bits())
+            }
+            fn cmp_ne(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_ne(rhs.cast_to_bits())
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialOrd<UIntType<Width>>
+            for $UIntInRangeType<Start, End>
+        {
+            fn cmp_lt(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_lt(rhs)
+            }
+            fn cmp_le(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_le(rhs)
+            }
+            fn cmp_gt(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_gt(rhs)
+            }
+            fn cmp_ge(lhs: Expr<Self>, rhs: Expr<UIntType<Width>>) -> Expr<Bool> {
+                lhs.cast_to_bits().cmp_ge(rhs)
+            }
+        }
+
+        impl<Start: Size, End: Size, Width: Size> ExprPartialOrd<$UIntInRangeType<Start, End>>
+            for UIntType<Width>
+        {
+            fn cmp_lt(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_lt(rhs.cast_to_bits())
+            }
+            fn cmp_le(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_le(rhs.cast_to_bits())
+            }
+            fn cmp_gt(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_gt(rhs.cast_to_bits())
+            }
+            fn cmp_ge(lhs: Expr<Self>, rhs: Expr<$UIntInRangeType<Start, End>>) -> Expr<Bool> {
+                lhs.cmp_ge(rhs.cast_to_bits())
+            }
+        }
+    };
+}
+
+define_uint_in_range_type! {
+    UIntInRange,
+    UIntInRangeType,
+    UIntInRangeTypeWithoutGenerics,
+    UIntInRangeTypeWithStart,
+    SerdeRange,
+    "..",
+    |start, end| UInt::range_usize(start..end),
+}
+
+define_uint_in_range_type! {
+    UIntInRangeInclusive,
+    UIntInRangeInclusiveType,
+    UIntInRangeInclusiveTypeWithoutGenerics,
+    UIntInRangeInclusiveTypeWithStart,
+    SerdeRangeInclusive,
+    "..=",
+    |start, end| UInt::range_inclusive_usize(start..=end),
+}
+
+impl SerdeRange<DynSize, DynSize> {
+    fn is_empty(self) -> bool {
+        self.start >= self.end
+    }
+}
+
+impl SerdeRangeInclusive<DynSize, DynSize> {
+    fn is_empty(self) -> bool {
+        self.start > self.end
+    }
+}
--- a/crates/fayalite/src/intern.rs
+++ b/crates/fayalite/src/intern.rs
--- a/crates/fayalite/src/intern/type_map.rs
+++ b/crates/fayalite/src/intern/type_map.rs
@ -1,10 +1,8 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
-use hashbrown::HashMap;
 use std::{
    any::{Any, TypeId},
    hash::{BuildHasher, Hasher},
-    ptr::NonNull,
    sync::RwLock,
 };

@ -75,59 +73,36 @@ impl BuildHasher for TypeIdBuildHasher {
    }
 }

-struct Value(NonNull<dyn Any + Send + Sync>);
-
-impl Value {
-    unsafe fn get_transmute_lifetime<'b>(&self) -> &'b (dyn Any + Send + Sync) {
-        unsafe { &*self.0.as_ptr() }
-    }
-    fn new(v: Box<dyn Any + Send + Sync>) -> Self {
-        unsafe { Self(NonNull::new_unchecked(Box::into_raw(v))) }
-    }
-}
-
-unsafe impl Send for Value {}
-unsafe impl Sync for Value {}
-
-impl Drop for Value {
-    fn drop(&mut self) {
-        unsafe { std::ptr::drop_in_place(self.0.as_ptr()) }
-    }
-}
-
-pub struct TypeIdMap(RwLock<HashMap<TypeId, Value, TypeIdBuildHasher>>);
+pub(crate) struct TypeIdMap(
+    RwLock<hashbrown::HashMap<TypeId, &'static (dyn Any + Send + Sync), TypeIdBuildHasher>>,
+);

 impl TypeIdMap {
-    pub const fn new() -> Self {
-        Self(RwLock::new(HashMap::with_hasher(TypeIdBuildHasher)))
+    pub(crate) const fn new() -> Self {
+        Self(RwLock::new(hashbrown::HashMap::with_hasher(
+            TypeIdBuildHasher,
+        )))
    }
    #[cold]
-    unsafe fn insert_slow(
+    fn insert_slow(
        &self,
        type_id: TypeId,
        make: fn() -> Box<dyn Any + Sync + Send>,
-    ) -> &(dyn Any + Sync + Send) {
-        let value = Value::new(make());
+    ) -> &'static (dyn Any + Sync + Send) {
+        let value = Box::leak(make());
        let mut write_guard = self.0.write().unwrap();
-        unsafe {
-            write_guard
-                .entry(type_id)
-                .or_insert(value)
-                .get_transmute_lifetime()
-        }
+        *write_guard.entry(type_id).or_insert(value)
    }
-    pub fn get_or_insert_default<T: Sized + Any + Send + Sync + Default>(&self) -> &T {
+    pub(crate) fn get_or_insert_default<T: Sized + Any + Send + Sync + Default>(&self) -> &T {
        let type_id = TypeId::of::<T>();
        let read_guard = self.0.read().unwrap();
-        let retval = read_guard
-            .get(&type_id)
-            .map(|v| unsafe { Value::get_transmute_lifetime(v) });
+        let retval = read_guard.get(&type_id).map(|v| *v);
        drop(read_guard);
        let retval = match retval {
            Some(retval) => retval,
-            None => unsafe { self.insert_slow(type_id, move || Box::new(T::default())) },
+            None => self.insert_slow(type_id, move || Box::new(T::default())),
        };
-        unsafe { &*(retval as *const dyn Any as *const T) }
+        retval.downcast_ref().expect("known to have correct TypeId")
    }
 }

--- a/crates/fayalite/src/lib.rs
+++ b/crates/fayalite/src/lib.rs
@ -11,8 +11,60 @@ extern crate self as fayalite;
 #[doc(hidden)]
 pub use std as __std;

+#[doc(hidden)]
+#[macro_export]
+macro_rules! __cfg_expansion_helper {
+    (
+        [
+            $($evaluated_cfgs:ident($($evaluated_exprs:tt)*) = $evaluated_results:ident,)*
+        ]
+        [
+            $cfg:ident($($expr:tt)*),
+            $($unevaluated_cfgs:ident($($unevaluated_exprs:tt)*),)*
+        ]
+        // pass as tt so we get right span for attribute
+        $after_evaluation_attr:tt $after_evaluation_body:tt
+    ) => {
+        #[$cfg($($expr)*)]
+        $crate::__cfg_expansion_helper! {
+            [
+                $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+                $cfg($($expr)*) = true,
+            ]
+            [
+                $($unevaluated_cfgs($($unevaluated_exprs)*),)*
+            ]
+            $after_evaluation_attr $after_evaluation_body
+        }
+        #[$cfg(not($($expr)*))]
+        $crate::__cfg_expansion_helper! {
+            [
+                $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+                $cfg($($expr)*) = false,
+            ]
+            [
+                $($unevaluated_cfgs($($unevaluated_exprs)*),)*
+            ]
+            $after_evaluation_attr $after_evaluation_body
+        }
+    };
+    (
+        [
+            $($evaluated_cfgs:ident($($evaluated_exprs:tt)*) = $evaluated_results:ident,)*
+        ]
+        []
+        // don't use #[...] so we get right span for `#` and `[]` of attribute
+        {$($after_evaluation_attr:tt)*} {$($after_evaluation_body:tt)*}
+    ) => {
+        $($after_evaluation_attr)*
+        #[__evaluated_cfgs([
+            $($evaluated_cfgs($($evaluated_exprs)*) = $evaluated_results,)*
+        ])]
+        $($after_evaluation_body)*
+    };
+}
+
 #[doc(inline)]
-#[doc(alias = "hdl")]
 /// The `#[hdl_module]` attribute is applied to a Rust function so that that function creates
 /// a [`Module`][`::fayalite::module::Module`] when called.
 /// In the function body it will implicitly create a
@ -21,6 +73,15 @@ pub use std as __std;
 /// See [Fayalite Modules][crate::_docs::modules]
 pub use fayalite_proc_macros::hdl_module;

+#[doc(inline)]
+pub use fayalite_proc_macros::hdl;
+
+pub use bitvec;
+
+/// struct used as a placeholder when applying defaults
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct __;
+
 #[cfg(feature = "unstable-doc")]
 pub mod _docs;

@ -32,15 +93,18 @@ pub mod clock;
 pub mod enum_;
 pub mod expr;
 pub mod firrtl;
+pub mod formal;
 pub mod int;
 pub mod intern;
 pub mod memory;
 pub mod module;
+pub mod phantom_const;
+pub mod prelude;
 pub mod reg;
 pub mod reset;
+pub mod sim;
 pub mod source_location;
+pub mod testing;
 pub mod ty;
-pub mod type_deduction;
 pub mod util;
-pub mod valueless;
 pub mod wire;
--- a/crates/fayalite/src/memory.rs
+++ b/crates/fayalite/src/memory.rs
@ -4,16 +4,16 @@
 #![allow(clippy::multiple_bound_locations)]
 use crate::{
    annotations::{Annotation, IntoAnnotations, TargetedAnnotation},
-    array::{Array, ArrayType, ArrayTypeTrait, ValueArrayOrSlice},
-    bundle::{BundleType, BundleValue, DynBundle, DynBundleType},
-    clock::{Clock, ClockType},
-    expr::{Expr, ExprEnum, ExprTrait, Flow, ToExpr},
-    int::{DynUInt, DynUIntType, UInt, UIntType},
+    array::{Array, ArrayType},
+    bundle::{Bundle, BundleType},
+    clock::Clock,
+    expr::{ops::BundleLiteral, repeat, Expr, Flow, ToExpr, ToLiteralBits},
+    hdl,
+    int::{Bool, DynSize, Size, UInt, UIntType},
    intern::{Intern, Interned},
    module::ScopedNameId,
    source_location::SourceLocation,
-    ty::{AsMask, DynCanonicalType, DynCanonicalValue, DynType, Type, Value},
-    type_deduction::HitUndeducedType,
+    ty::{AsMask, CanonicalType, Type},
    util::DebugAsDisplay,
 };
 use bitvec::slice::BitSlice;
@ -21,37 +21,37 @@ use std::{
    cell::RefCell,
    fmt,
    hash::{Hash, Hasher},
-    num::NonZeroU32,
+    marker::PhantomData,
+    num::NonZeroUsize,
    rc::Rc,
 };

-#[derive(Value, Clone, PartialEq, Eq, Hash, Debug)]
-pub struct ReadStruct<Element> {
-    pub addr: DynUInt,
-    pub en: UInt<1>,
+#[hdl]
+pub struct ReadStruct<Element, AddrWidth: Size> {
+    pub addr: UIntType<AddrWidth>,
+    pub en: Bool,
    pub clk: Clock,
    #[hdl(flip)]
    pub data: Element,
 }

-#[derive(Value, Clone, PartialEq, Eq, Hash, Debug)]
-pub struct WriteStruct<Element: Value> {
-    pub addr: DynUInt,
-    pub en: UInt<1>,
+#[hdl]
+pub struct WriteStruct<Element, AddrWidth: Size> {
+    pub addr: UIntType<AddrWidth>,
+    pub en: Bool,
    pub clk: Clock,
    pub data: Element,
    pub mask: AsMask<Element>,
 }

-#[allow(clippy::multiple_bound_locations)]
-#[derive(Value, Clone, PartialEq, Eq, Hash, Debug)]
-pub struct ReadWriteStruct<Element: Value> {
-    pub addr: DynUInt,
-    pub en: UInt<1>,
+#[hdl]
+pub struct ReadWriteStruct<Element, AddrWidth: Size> {
+    pub addr: UIntType<AddrWidth>,
+    pub en: Bool,
    pub clk: Clock,
    #[hdl(flip)]
    pub rdata: Element,
-    pub wmode: UInt<1>,
+    pub wmode: Bool,
    pub wdata: Element,
    pub wmask: AsMask<Element>,
 }
@ -64,11 +64,10 @@ pub trait PortType:
    sealed::Sealed + Clone + Eq + Hash + fmt::Debug + Send + Sync + 'static
 {
    type PortKindTy: Copy + Eq + Hash + fmt::Debug + Send + Sync + 'static;
-    type PortType: BundleType<Value = Self::PortValue>;
-    type PortValue: BundleValue<Type = Self::PortType>;
+    type Port: BundleType;
    fn port_kind(port_kind: Self::PortKindTy) -> PortKind;
    fn from_port_kind(port_kind: PortKind) -> Self::PortKindTy;
-    fn port_ty(port: &MemPort<Self>) -> Self::PortType;
+    fn port_ty(port: &MemPort<Self>) -> Self::Port;
 }

 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
@ -80,8 +79,7 @@ impl sealed::Sealed for DynPortType {}

 impl PortType for DynPortType {
    type PortKindTy = PortKind;
-    type PortType = DynBundleType;
-    type PortValue = DynBundle;
+    type Port = Bundle;

    fn port_kind(port_kind: Self::PortKindTy) -> PortKind {
        port_kind
@ -91,41 +89,38 @@ impl PortType for DynPortType {
        port_kind
    }

-    fn port_ty(port: &MemPort<Self>) -> Self::PortType {
-        match port.port_kind {
-            PortKind::ReadOnly => MemPort::<ReadStruct<DynCanonicalValue>>::from_canonical(*port)
-                .ty()
-                .canonical(),
-            PortKind::WriteOnly => MemPort::<WriteStruct<DynCanonicalValue>>::from_canonical(*port)
-                .ty()
-                .canonical(),
-            PortKind::ReadWrite => {
-                MemPort::<ReadWriteStruct<DynCanonicalValue>>::from_canonical(*port)
+    fn port_ty(port: &MemPort<Self>) -> Self::Port {
+        Bundle::new(match port.port_kind {
+            PortKind::ReadOnly => {
+                MemPort::<ReadStruct<CanonicalType, DynSize>>::from_canonical(*port)
                    .ty()
-                    .canonical()
+                    .fields()
            }
-        }
+            PortKind::WriteOnly => {
+                MemPort::<WriteStruct<CanonicalType, DynSize>>::from_canonical(*port)
+                    .ty()
+                    .fields()
+            }
+            PortKind::ReadWrite => {
+                MemPort::<ReadWriteStruct<CanonicalType, DynSize>>::from_canonical(*port)
+                    .ty()
+                    .fields()
+            }
+        })
    }
 }

-pub trait PortStruct:
-    BundleValue
-    + sealed::Sealed
-    + PortType<PortKindTy = (), PortType = <Self as ToExpr>::Type, PortValue = Self>
-where
-    Self::Type: BundleType<Value = Self>,
-{
-    type Element: Value<Type = Self::ElementType>;
-    type ElementType: Type<Value = Self::Element>;
+pub trait PortStruct: BundleType + sealed::Sealed + PortType<PortKindTy = (), Port = Self> {
+    type Element: Type;
    const PORT_KIND: PortKind;

-    fn addr(this: Expr<Self>) -> Expr<DynUInt>;
-    fn en(this: Expr<Self>) -> Expr<UInt<1>>;
+    fn addr(this: Expr<Self>) -> Expr<UInt>;
+    fn en(this: Expr<Self>) -> Expr<Bool>;
    fn clk(this: Expr<Self>) -> Expr<Clock>;
    fn rdata(this: Expr<Self>) -> Option<Expr<Self::Element>>;
    fn wdata(this: Expr<Self>) -> Option<Expr<Self::Element>>;
    fn wmask(this: Expr<Self>) -> Option<Expr<AsMask<Self::Element>>>;
-    fn wmode(this: Expr<Self>) -> Expr<UInt<1>>;
+    fn wmode(this: Expr<Self>) -> Expr<Bool>;
 }

 macro_rules! impl_port_struct {
@ -138,19 +133,11 @@ macro_rules! impl_port_struct {
            $($body:tt)*
        }
    ) => {
-        impl<$Element: Value> sealed::Sealed for $Struct<$Element>
-        where
-            $Element::Type: Type<Value = $Element>,
-        {
-        }
+        impl<$Element: Type> sealed::Sealed for $Struct<$Element, DynSize> {}

-        impl<$Element: Value> PortType for $Struct<$Element>
-        where
-            $Element::Type: Type<Value = $Element>,
-        {
+        impl<$Element: Type> PortType for $Struct<$Element, DynSize> {
            type PortKindTy = ();
-            type PortType = <Self as ToExpr>::Type;
-            type PortValue = Self;
+            type Port = Self;

            fn port_kind(_port_kind: Self::PortKindTy) -> PortKind {
                Self::PORT_KIND
@ -165,18 +152,14 @@ macro_rules! impl_port_struct {
            }
        }

-        impl<$Element: Value> PortStruct for $Struct<$Element>
-        where
-            $Element::Type: Type<Value = $Element>,
-        {
+        impl<$Element: Type> PortStruct for $Struct<$Element, DynSize> {
            type Element = $Element;
-            type ElementType = $Element::Type;

-            fn addr(this: Expr<Self>) -> Expr<DynUInt> {
+            fn addr(this: Expr<Self>) -> Expr<UInt> {
                this.addr
            }

-            fn en(this: Expr<Self>) -> Expr<UInt<1>> {
+            fn en(this: Expr<Self>) -> Expr<Bool> {
                this.en
            }

@ -191,14 +174,9 @@ macro_rules! impl_port_struct {

 impl_port_struct! {
    impl<Element> _ for ReadStruct {
-        fn port_ty(port: &MemPort<Self>) -> <MemPort<Self> as ToExpr>::Type {
-            type T<V> = <V as ToExpr>::Type;
-            T::<Self> {
-                addr: port.addr_type,
-                en: UIntType::new(),
-                clk: ClockType,
-                data: Element::Type::from_dyn_canonical_type(port.mem_element_type),
-            }
+        fn port_ty(port: &MemPort<Self>) -> Self {
+            let element = Element::from_canonical(port.mem_element_type);
+            ReadStruct[element][port.addr_type.width()]
        }

        const PORT_KIND: PortKind = PortKind::ReadOnly;
@ -215,7 +193,7 @@ impl_port_struct! {
            None
        }

-        fn wmode(_this: Expr<Self>) -> Expr<UInt<1>> {
+        fn wmode(_this: Expr<Self>) -> Expr<Bool> {
            false.to_expr()
        }
    }
@ -223,16 +201,9 @@ impl_port_struct! {

 impl_port_struct! {
    impl<Element> _ for WriteStruct {
-        fn port_ty(port: &MemPort<Self>) -> <MemPort<Self> as ToExpr>::Type {
-            type T<V> = <V as ToExpr>::Type;
-            let element_ty = Element::Type::from_dyn_canonical_type(port.mem_element_type);
-            T::<Self> {
-                addr: port.addr_type,
-                en: UIntType::new(),
-                clk: ClockType,
-                mask: element_ty.mask_type(),
-                data: element_ty,
-            }
+        fn port_ty(port: &MemPort<Self>) -> Self {
+            let element = Element::from_canonical(port.mem_element_type);
+            WriteStruct[element][port.addr_type.width()]
        }

        const PORT_KIND: PortKind = PortKind::WriteOnly;
@ -249,7 +220,7 @@ impl_port_struct! {
            Some(this.mask)
        }

-        fn wmode(_this: Expr<Self>) -> Expr<UInt<1>> {
+        fn wmode(_this: Expr<Self>) -> Expr<Bool> {
            true.to_expr()
        }
    }
@ -257,18 +228,9 @@ impl_port_struct! {

 impl_port_struct! {
    impl<Element> _ for ReadWriteStruct {
-        fn port_ty(port: &MemPort<Self>) -> <MemPort<Self> as ToExpr>::Type {
-            type T<V> = <V as ToExpr>::Type;
-            let element_ty = Element::Type::from_dyn_canonical_type(port.mem_element_type);
-            T::<Self> {
-                addr: port.addr_type,
-                en: UIntType::new(),
-                clk: ClockType,
-                rdata: element_ty.clone(),
-                wmode: UIntType::new(),
-                wmask: element_ty.mask_type(),
-                wdata: element_ty,
-            }
+        fn port_ty(port: &MemPort<Self>) -> Self {
+            let element = Element::from_canonical(port.mem_element_type);
+            ReadWriteStruct[element][port.addr_type.width()]
        }

        const PORT_KIND: PortKind = PortKind::ReadWrite;
@ -285,7 +247,7 @@ impl_port_struct! {
            Some(this.wmask)
        }

-        fn wmode(this: Expr<Self>) -> Expr<UInt<1>> {
+        fn wmode(this: Expr<Self>) -> Expr<Bool> {
            this.wmode
        }
    }
@ -383,42 +345,31 @@ pub struct MemPort<T: PortType> {
    source_location: SourceLocation,
    port_kind: T::PortKindTy,
    port_index: usize,
-    addr_type: DynUIntType,
-    mem_element_type: Interned<dyn DynCanonicalType>,
+    addr_type: UInt,
+    mem_element_type: CanonicalType,
 }

 impl<T: PortType> fmt::Debug for MemPort<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let Self {
-            mem_name,
-            source_location: _,
-            port_kind: _,
-            port_index: _,
-            addr_type,
-            mem_element_type,
-        } = self;
-        f.debug_struct("MemPort")
-            .field("mem_name", mem_name)
-            .field("port_name", &self.port_name())
-            .field("addr_type", addr_type)
-            .field("mem_element_type", mem_element_type)
-            .finish_non_exhaustive()
-    }
-}
-
-impl<T: PortType> ToExpr for MemPort<T> {
-    type Type = T::PortType;
-
-    fn ty(&self) -> Self::Type {
-        T::port_ty(self)
-    }
-
-    fn to_expr(&self) -> Expr<<Self::Type as Type>::Value> {
-        Expr::new_unchecked(self.expr_enum())
+        f.write_str("MemPort(")?;
+        self.mem_name.fmt(f)?;
+        f.write_str(".")?;
+        self.port_name().fmt(f)?;
+        f.write_str(": ")?;
+        match self.port_kind() {
+            PortKind::ReadOnly => f.write_str("ReadStruct<")?,
+            PortKind::WriteOnly => f.write_str("WriteStruct<")?,
+            PortKind::ReadWrite => f.write_str("ReadWriteStruct<")?,
+        }
+        self.mem_element_type.fmt(f)?;
+        f.write_str(">)")
    }
 }

 impl<T: PortType> MemPort<T> {
+    pub fn ty(&self) -> T::Port {
+        T::port_ty(self)
+    }
    pub fn source_location(&self) -> SourceLocation {
        self.source_location
    }
@ -437,10 +388,10 @@ impl<T: PortType> MemPort<T> {
            index: self.port_index,
        }
    }
-    pub fn mem_element_type(&self) -> Interned<dyn DynCanonicalType> {
+    pub fn mem_element_type(&self) -> CanonicalType {
        self.mem_element_type
    }
-    pub fn addr_type(&self) -> DynUIntType {
+    pub fn addr_type(&self) -> UInt {
        self.addr_type
    }
    pub fn canonical(&self) -> MemPort<DynPortType> {
@ -464,7 +415,6 @@ impl<T: PortType> MemPort<T> {
    pub fn from_canonical(port: MemPort<DynPortType>) -> Self
    where
        T: PortStruct,
-        T::Type: BundleType<Value = T>,
    {
        let MemPort {
            mem_name,
@ -489,11 +439,11 @@ impl<T: PortType> MemPort<T> {
        mem_name: ScopedNameId,
        source_location: SourceLocation,
        port_name: PortName,
-        addr_type: DynUIntType,
-        mem_element_type: Interned<dyn DynCanonicalType>,
+        addr_type: UInt,
+        mem_element_type: CanonicalType,
    ) -> Self {
        assert!(
-            mem_element_type.is_storable().unwrap_or(true),
+            mem_element_type.is_storable(),
            "memory element type must be a storable type"
        );
        Self {
@ -520,25 +470,25 @@ pub enum ReadUnderWrite {
    Undefined,
 }

-#[derive(Copy, Clone, PartialEq, Eq, Hash)]
-struct MemImpl<T: ArrayTypeTrait, P> {
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+struct MemImpl<Element: Type, Len: Size, P> {
    scoped_name: ScopedNameId,
    source_location: SourceLocation,
-    array_type: T,
+    array_type: ArrayType<Element, Len>,
    initial_value: Option<Interned<BitSlice>>,
    ports: P,
    read_latency: usize,
-    write_latency: NonZeroU32,
+    write_latency: NonZeroUsize,
    read_under_write: ReadUnderWrite,
    port_annotations: Interned<[TargetedAnnotation]>,
    mem_annotations: Interned<[Annotation]>,
 }

-pub struct Mem<VA: ValueArrayOrSlice + ?Sized>(
-    Interned<MemImpl<ArrayType<VA>, Interned<[Interned<MemPort<DynPortType>>]>>>,
+pub struct Mem<Element: Type = CanonicalType, Len: Size = DynSize>(
+    Interned<MemImpl<Element, Len, Interned<[MemPort<DynPortType>]>>>,
 );

-struct PortsDebug<'a>(&'a [Interned<MemPort<DynPortType>>]);
+struct PortsDebug<'a>(&'a [MemPort<DynPortType>]);

 impl fmt::Debug for PortsDebug<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@ -552,7 +502,7 @@ impl fmt::Debug for PortsDebug<'_> {
    }
 }

-impl<VA: ValueArrayOrSlice + ?Sized> fmt::Debug for Mem<VA> {
+impl<Element: Type, Len: Size> fmt::Debug for Mem<Element, Len> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let MemImpl {
            scoped_name,
@ -569,7 +519,12 @@ impl<VA: ValueArrayOrSlice + ?Sized> fmt::Debug for Mem<VA> {
        f.debug_struct("Mem")
            .field("name", scoped_name)
            .field("array_type", array_type)
-            .field("initial_value", initial_value)
+            .field(
+                "initial_value",
+                &initial_value.as_ref().map(|initial_value| {
+                    DebugMemoryData::from_bit_slice(*array_type, initial_value)
+                }),
+            )
            .field("read_latency", read_latency)
            .field("write_latency", write_latency)
            .field("read_under_write", read_under_write)
@ -580,54 +535,54 @@ impl<VA: ValueArrayOrSlice + ?Sized> fmt::Debug for Mem<VA> {
    }
 }

-impl<VA: ValueArrayOrSlice + ?Sized> Hash for Mem<VA> {
+impl<Element: Type, Len: Size> Hash for Mem<Element, Len> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.0.hash(state);
    }
 }

-impl<VA: ValueArrayOrSlice + ?Sized> Eq for Mem<VA> {}
+impl<Element: Type, Len: Size> Eq for Mem<Element, Len> {}

-impl<VA: ValueArrayOrSlice + ?Sized> PartialEq for Mem<VA> {
+impl<Element: Type, Len: Size> PartialEq for Mem<Element, Len> {
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
 }

-impl<VA: ValueArrayOrSlice + ?Sized> Copy for Mem<VA> {}
+impl<Element: Type, Len: Size> Copy for Mem<Element, Len> {}

-impl<VA: ValueArrayOrSlice + ?Sized> Clone for Mem<VA> {
+impl<Element: Type, Len: Size> Clone for Mem<Element, Len> {
    fn clone(&self) -> Self {
        *self
    }
 }

-impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
+impl<Element: Type, Len: Size> Mem<Element, Len> {
    #[allow(clippy::too_many_arguments)]
    #[track_caller]
    pub fn new_unchecked(
        scoped_name: ScopedNameId,
        source_location: SourceLocation,
-        array_type: ArrayType<VA>,
+        array_type: ArrayType<Element, Len>,
        initial_value: Option<Interned<BitSlice>>,
-        ports: Interned<[Interned<MemPort<DynPortType>>]>,
+        ports: Interned<[MemPort<DynPortType>]>,
        read_latency: usize,
-        write_latency: NonZeroU32,
+        write_latency: NonZeroUsize,
        read_under_write: ReadUnderWrite,
        port_annotations: Interned<[TargetedAnnotation]>,
        mem_annotations: Interned<[Annotation]>,
    ) -> Self {
        if let Some(initial_value) = initial_value {
-            MemBuilder::<VA>::check_initial_value_bit_slice(
+            MemBuilder::<Element, Len>::check_initial_value_bit_slice(
                array_type.element(),
                Some(array_type.len()),
                initial_value,
            );
        }
        let addr_width = memory_addr_width(array_type.len());
-        let expected_mem_element_type = array_type.element().canonical_dyn();
+        let expected_mem_element_type = array_type.element().canonical();
        assert!(
-            expected_mem_element_type.is_storable().unwrap_or(true),
+            expected_mem_element_type.is_storable(),
            "memory element type must be a storable type"
        );
        for (index, port) in ports.iter().enumerate() {
@ -638,7 +593,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
                port_index,
                addr_type,
                mem_element_type,
-            } = **port;
+            } = *port;
            assert_eq!(mem_name, scoped_name, "memory name must match with ports");
            assert_eq!(
                port_index, index,
@ -660,7 +615,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
            };
            assert_eq!(
                Some(port),
-                ports.get(port.port_index).map(|v| &**v),
+                ports.get(port.port_index),
                "port on memory must match annotation's target base"
            );
        }
@ -683,19 +638,19 @@ impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
    pub fn source_location(self) -> SourceLocation {
        self.0.source_location
    }
-    pub fn array_type(self) -> ArrayType<VA> {
-        self.0.array_type.clone()
+    pub fn array_type(self) -> ArrayType<Element, Len> {
+        self.0.array_type
    }
    pub fn initial_value(self) -> Option<Interned<BitSlice>> {
        self.0.initial_value
    }
-    pub fn ports(self) -> Interned<[Interned<MemPort<DynPortType>>]> {
+    pub fn ports(self) -> Interned<[MemPort<DynPortType>]> {
        self.0.ports
    }
    pub fn read_latency(self) -> usize {
        self.0.read_latency
    }
-    pub fn write_latency(self) -> NonZeroU32 {
+    pub fn write_latency(self) -> NonZeroUsize {
        self.0.write_latency
    }
    pub fn read_under_write(self) -> ReadUnderWrite {
@ -707,7 +662,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
    pub fn mem_annotations(self) -> Interned<[Annotation]> {
        self.0.mem_annotations
    }
-    pub fn canonical(self) -> Mem<[DynCanonicalValue]> {
+    pub fn canonical(self) -> Mem {
        let MemImpl {
            scoped_name,
            source_location,
@ -720,7 +675,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> Mem<VA> {
            port_annotations,
            mem_annotations,
        } = *self.0;
-        let array_type = array_type.canonical();
+        let array_type = array_type.as_dyn_array();
        Mem(Intern::intern_sized(MemImpl {
            scoped_name,
            source_location,
@ -752,23 +707,23 @@ impl<T: fmt::Debug> fmt::Debug for MaybeSpecified<T> {
 pub(crate) struct MemBuilderTarget {
    pub(crate) scoped_name: ScopedNameId,
    pub(crate) source_location: SourceLocation,
-    pub(crate) mem_element_type: Interned<dyn DynCanonicalType>,
+    pub(crate) mem_element_type: CanonicalType,
    pub(crate) depth: Option<usize>,
    pub(crate) initial_value: Option<Interned<BitSlice>>,
-    pub(crate) ports: Vec<Interned<MemPort<DynPortType>>>,
+    pub(crate) ports: Vec<MemPort<DynPortType>>,
    pub(crate) read_latency: usize,
-    pub(crate) write_latency: NonZeroU32,
+    pub(crate) write_latency: NonZeroUsize,
    pub(crate) read_under_write: ReadUnderWrite,
    pub(crate) port_annotations: Vec<TargetedAnnotation>,
    pub(crate) mem_annotations: Vec<Annotation>,
 }

 impl MemBuilderTarget {
-    pub(crate) fn make_memory(&self) -> Option<Mem<[DynCanonicalValue]>> {
+    pub(crate) fn make_memory(&self) -> Option<Mem> {
        Some(Mem::new_unchecked(
            self.scoped_name,
            self.source_location,
-            ArrayType::new_slice(self.mem_element_type, self.depth?),
+            ArrayType::new_dyn(self.mem_element_type, self.depth?),
            self.initial_value,
            Intern::intern(&self.ports),
            self.read_latency,
@ -818,16 +773,18 @@ impl fmt::Debug for MemBuilderTarget {
    }
 }

-pub struct MemBuilder<VA: ValueArrayOrSlice + ?Sized> {
-    mem_element_type: VA::ElementType,
+pub struct MemBuilder<Element: Type, Len: Size = DynSize> {
+    mem_element_type: Element,
    target: Rc<RefCell<MemBuilderTarget>>,
+    _phantom: PhantomData<Len>,
 }

-impl<VA: ValueArrayOrSlice + ?Sized> fmt::Debug for MemBuilder<VA> {
+impl<Element: Type, Len: Size> fmt::Debug for MemBuilder<Element, Len> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let Self {
            mem_element_type,
            target,
+            _phantom: _,
        } = &self;
        target.borrow().debug_fmt("MemBuilder", mem_element_type, f)
    }
@ -839,29 +796,28 @@ pub fn memory_addr_width(depth: usize) -> usize {
        .map_or(usize::BITS, usize::ilog2) as usize
 }

-impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
+impl<Element: Type, Len: Size> MemBuilder<Element, Len> {
    #[track_caller]
    fn check_initial_value_bit_slice(
-        mem_element_type: &VA::ElementType,
+        mem_element_type: Element,
        depth: Option<usize>,
        initial_value: Interned<BitSlice>,
    ) -> Interned<BitSlice> {
+        let element_bit_width = mem_element_type.canonical().bit_width();
        if let Some(depth) = depth {
-            if let Ok(mem_element_bit_width) = mem_element_type.bit_width() {
-                let expected_len = depth.checked_mul(mem_element_bit_width).expect(
-                    "memory must be small enough that its initializer bit length fits in usize",
-                );
-                assert_eq!(
-                    expected_len,
-                    initial_value.len(),
-                    "Mem's initializer bit length doesn't match the expected value",
-                );
-            }
+            let expected_len = depth.checked_mul(element_bit_width).expect(
+                "memory must be small enough that its initializer bit length fits in usize",
+            );
+            assert_eq!(
+                expected_len,
+                initial_value.len(),
+                "Mem's initializer bit length doesn't match the expected value",
+            );
        }
        assert!(
            initial_value
                .len()
-                .checked_rem(mem_element_type.bit_width().unwrap_or(1))
+                .checked_rem(element_bit_width)
                .unwrap_or(initial_value.len())
                == 0,
            "Mem's initializer bit length must be a multiple of the element type's bit width",
@ -870,14 +826,14 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
    }
    #[track_caller]
    fn check_initial_value_expr(
-        mem_element_type: &VA::ElementType,
+        mem_element_type: &Element,
        depth: Option<usize>,
-        initial_value: Expr<Array<[DynCanonicalValue]>>,
+        initial_value: Expr<Array>,
    ) -> Interned<BitSlice> {
-        let initial_value_ty = initial_value.canonical_type();
+        let initial_value_ty = Expr::ty(initial_value);
        assert_eq!(
            *mem_element_type,
-            <VA::ElementType as DynType>::from_dyn_canonical_type(*initial_value_ty.element()),
+            Element::from_canonical(initial_value_ty.element()),
            "Mem's element type must match initializer's element type",
        );
        if let Some(depth) = depth {
@ -890,18 +846,9 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
        let Ok(retval) = initial_value.to_literal_bits() else {
            panic!("Mem's initializer must be convertible to literal bits");
        };
-        let retval = match retval {
-            Ok(retval) => retval,
-            Err(HitUndeducedType { .. }) => {
-                todo!(
-                    "Mem's initializer contains undeduced types, \
-                    you can work around this by using only hdl(static) types"
-                )
-            }
-        };
        debug_assert_eq!(
-            Ok(retval.len()),
-            initial_value_ty.bit_width(),
+            retval.len(),
+            initial_value_ty.type_properties().bit_width,
            "initial value produced wrong literal bits length"
        );
        retval
@ -910,22 +857,22 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
    pub(crate) fn new(
        scoped_name: ScopedNameId,
        source_location: SourceLocation,
-        mem_element_type: VA::ElementType,
+        mem_element_type: Element,
    ) -> (Self, Rc<RefCell<MemBuilderTarget>>) {
-        let canonical_mem_element_type = mem_element_type.canonical_dyn();
+        let canonical_mem_element_type = mem_element_type.canonical();
        assert!(
-            canonical_mem_element_type.is_storable().unwrap_or(true),
+            canonical_mem_element_type.is_storable(),
            "memory element type must be a storable type"
        );
        let target = Rc::new(RefCell::new(MemBuilderTarget {
            scoped_name,
            source_location,
            mem_element_type: canonical_mem_element_type,
-            depth: VA::FIXED_LEN_TYPE.map(VA::len_from_len_type),
+            depth: Len::KNOWN_VALUE,
            initial_value: None,
            ports: vec![],
            read_latency: 0,
-            write_latency: NonZeroU32::new(1).unwrap(),
+            write_latency: NonZeroUsize::new(1).unwrap(),
            read_under_write: ReadUnderWrite::Old,
            port_annotations: vec![],
            mem_annotations: vec![],
@ -934,6 +881,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
            Self {
                mem_element_type,
                target: Rc::clone(&target),
+                _phantom: PhantomData,
            },
            target,
        )
@ -943,19 +891,19 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
        &mut self,
        source_location: SourceLocation,
        port_kind: PortKind,
-    ) -> Interned<MemPort<DynPortType>> {
+    ) -> MemPort<DynPortType> {
        let mut target = self.target.borrow_mut();
        let Some(depth) = target.depth else {
            panic!("MemBuilder::depth must be called before adding ports");
        };
-        let port = Intern::intern_sized(MemPort {
+        let port = MemPort {
            mem_name: target.scoped_name,
            source_location,
            port_kind,
            port_index: target.ports.len(),
-            addr_type: DynUIntType::new(memory_addr_width(depth)),
+            addr_type: UInt::new(memory_addr_width(depth)),
            mem_element_type: target.mem_element_type,
-        });
+        };
        target.ports.push(port);
        port
    }
@ -964,50 +912,53 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
        &mut self,
        source_location: SourceLocation,
        kind: PortKind,
-    ) -> Expr<DynBundle> {
-        Expr::new_unchecked(ExprEnum::MemPort(self.new_port_impl(source_location, kind)))
+    ) -> Expr<Bundle> {
+        self.new_port_impl(source_location, kind).to_expr()
    }
    #[track_caller]
-    pub fn new_port(&mut self, kind: PortKind) -> Expr<DynBundle> {
+    pub fn new_port(&mut self, kind: PortKind) -> Expr<Bundle> {
        self.new_port_with_loc(SourceLocation::caller(), kind)
    }
    #[track_caller]
    pub fn new_read_port_with_loc(
        &mut self,
        source_location: SourceLocation,
-    ) -> Expr<ReadStruct<VA::Element>> {
-        Expr::new_unchecked(ExprEnum::MemPort(
-            self.new_port_impl(source_location, PortKind::ReadOnly),
-        ))
+    ) -> Expr<ReadStruct<Element, DynSize>> {
+        Expr::from_bundle(
+            self.new_port_impl(source_location, PortKind::ReadOnly)
+                .to_expr(),
+        )
    }
    #[track_caller]
-    pub fn new_read_port(&mut self) -> Expr<ReadStruct<VA::Element>> {
+    pub fn new_read_port(&mut self) -> Expr<ReadStruct<Element, DynSize>> {
        self.new_read_port_with_loc(SourceLocation::caller())
    }
    #[track_caller]
    pub fn new_write_port_with_loc(
        &mut self,
        source_location: SourceLocation,
-    ) -> Expr<WriteStruct<VA::Element>> {
-        Expr::new_unchecked(ExprEnum::MemPort(
-            self.new_port_impl(source_location, PortKind::WriteOnly),
-        ))
+    ) -> Expr<WriteStruct<Element, DynSize>> {
+        Expr::from_bundle(
+            self.new_port_impl(source_location, PortKind::WriteOnly)
+                .to_expr(),
+        )
    }
    #[track_caller]
-    pub fn new_write_port(&mut self) -> Expr<WriteStruct<VA::Element>> {
+    pub fn new_write_port(&mut self) -> Expr<WriteStruct<Element, DynSize>> {
        self.new_write_port_with_loc(SourceLocation::caller())
    }
    #[track_caller]
    pub fn new_rw_port_with_loc(
        &mut self,
        source_location: SourceLocation,
-    ) -> Expr<ReadWriteStruct<VA::Element>> {
-        Expr::new_unchecked(ExprEnum::MemPort(
-            self.new_port_impl(source_location, PortKind::ReadWrite),
-        ))
+    ) -> Expr<ReadWriteStruct<Element, DynSize>> {
+        Expr::from_bundle(
+            self.new_port_impl(source_location, PortKind::ReadWrite)
+                .to_expr(),
+        )
    }
    #[track_caller]
-    pub fn new_rw_port(&mut self) -> Expr<ReadWriteStruct<VA::Element>> {
+    pub fn new_rw_port(&mut self) -> Expr<ReadWriteStruct<Element, DynSize>> {
        self.new_rw_port_with_loc(SourceLocation::caller())
    }
    pub fn scoped_name(&self) -> ScopedNameId {
@ -1016,7 +967,7 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
    pub fn source_location(&self) -> SourceLocation {
        self.target.borrow().source_location
    }
-    pub fn get_mem_element_type(&self) -> &VA::ElementType {
+    pub fn get_mem_element_type(&self) -> &Element {
        &self.mem_element_type
    }
    #[allow(clippy::result_unit_err)]
@ -1039,28 +990,28 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
        target.depth = Some(depth);
    }
    #[allow(clippy::result_unit_err)]
-    pub fn get_array_type(&self) -> Result<ArrayType<VA>, ()> {
-        Ok(ArrayType::new_with_len(
-            self.mem_element_type.clone(),
-            self.get_depth()?,
+    pub fn get_array_type(&self) -> Result<ArrayType<Element, Len>, ()> {
+        Ok(ArrayType::new(
+            self.mem_element_type,
+            Len::from_usize(self.get_depth()?),
        ))
    }
    pub fn get_initial_value(&self) -> Option<Interned<BitSlice>> {
        self.target.borrow().initial_value
    }
    #[track_caller]
-    pub fn initial_value(&mut self, initial_value: impl ToExpr<Type = ArrayType<VA>>) {
+    pub fn initial_value(&mut self, initial_value: impl ToExpr<Type = ArrayType<Element, Len>>) {
        let mut target = self.target.borrow_mut();
        if target.initial_value.is_some() {
            panic!("can't set Mem's initial value more than once");
        }
-        let initial_value = initial_value.to_expr().canonical();
+        let initial_value = Expr::as_dyn_array(initial_value.to_expr());
        target.initial_value = Some(Self::check_initial_value_expr(
            &self.mem_element_type,
            target.depth,
            initial_value,
        ));
-        target.depth = Some(initial_value.ty().len());
+        target.depth = Some(Expr::ty(initial_value).len());
    }
    #[track_caller]
    pub fn initial_value_bit_slice(&mut self, initial_value: Interned<BitSlice>) {
@ -1069,14 +1020,13 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
            panic!("can't set Mem's initial value more than once");
        }
        target.initial_value = Some(Self::check_initial_value_bit_slice(
-            &self.mem_element_type,
+            self.mem_element_type,
            target.depth,
            initial_value,
        ));
-        if let Ok(element_bit_width) = self.mem_element_type.bit_width() {
-            if element_bit_width != 0 {
-                target.depth = Some(initial_value.len() / element_bit_width);
-            }
+        let element_bit_width = self.mem_element_type.canonical().bit_width();
+        if element_bit_width != 0 {
+            target.depth = Some(initial_value.len() / element_bit_width);
        }
    }
    pub fn get_read_latency(&self) -> usize {
@ -1085,10 +1035,10 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
    pub fn read_latency(&mut self, read_latency: usize) {
        self.target.borrow_mut().read_latency = read_latency;
    }
-    pub fn get_write_latency(&self) -> NonZeroU32 {
+    pub fn get_write_latency(&self) -> NonZeroUsize {
        self.target.borrow().write_latency
    }
-    pub fn write_latency(&mut self, write_latency: NonZeroU32) {
+    pub fn write_latency(&mut self, write_latency: NonZeroUsize) {
        self.target.borrow_mut().write_latency = write_latency;
    }
    pub fn get_read_under_write(&self) -> ReadUnderWrite {
@ -1105,3 +1055,91 @@ impl<VA: ValueArrayOrSlice + ?Sized> MemBuilder<VA> {
            .extend(annotations.into_annotations());
    }
 }
+
+pub fn splat_mask<T: Type>(ty: T, value: Expr<Bool>) -> Expr<AsMask<T>> {
+    let canonical_ty = ty.canonical();
+    match canonical_ty {
+        CanonicalType::UInt(_)
+        | CanonicalType::SInt(_)
+        | CanonicalType::Bool(_)
+        | CanonicalType::AsyncReset(_)
+        | CanonicalType::SyncReset(_)
+        | CanonicalType::Reset(_)
+        | CanonicalType::Clock(_)
+        | CanonicalType::Enum(_) => Expr::from_canonical(Expr::canonical(value)),
+        CanonicalType::Array(array) => Expr::from_canonical(Expr::canonical(repeat(
+            splat_mask(array.element(), value),
+            array.len(),
+        ))),
+        CanonicalType::Bundle(bundle) => Expr::from_canonical(Expr::canonical(
+            BundleLiteral::new(
+                bundle.mask_type(),
+                bundle
+                    .fields()
+                    .iter()
+                    .map(|field| splat_mask(field.ty, value))
+                    .collect(),
+            )
+            .to_expr(),
+        )),
+        CanonicalType::PhantomConst(_) => Expr::from_canonical(Expr::canonical(().to_expr())),
+    }
+}
+
+pub trait DebugMemoryDataGetElement {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice;
+}
+
+impl<'a, F: ?Sized + Fn(usize, Array) -> &'a BitSlice> DebugMemoryDataGetElement for &'a F {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice {
+        self(element_index, array_type)
+    }
+}
+
+#[derive(Clone)]
+pub struct DebugMemoryData<GetElement: DebugMemoryDataGetElement> {
+    pub array_type: Array,
+    pub get_element: GetElement,
+}
+
+impl DebugMemoryDataGetElement for &'_ BitSlice {
+    fn get_element(&self, element_index: usize, array_type: Array) -> &BitSlice {
+        assert!(element_index < array_type.len());
+        let stride = array_type.element().bit_width();
+        let start = element_index
+            .checked_mul(stride)
+            .expect("memory is too big");
+        let end = start.checked_add(stride).expect("memory is too big");
+        &self[start..end]
+    }
+}
+
+impl<'a> DebugMemoryData<&'a BitSlice> {
+    pub fn from_bit_slice<T: Type, Depth: Size>(
+        array_type: ArrayType<T, Depth>,
+        bit_slice: &'a BitSlice,
+    ) -> Self {
+        let array_type = array_type.as_dyn_array();
+        assert_eq!(bit_slice.len(), array_type.type_properties().bit_width);
+        Self {
+            array_type,
+            get_element: bit_slice,
+        }
+    }
+}
+
+impl<GetElement: DebugMemoryDataGetElement> fmt::Debug for DebugMemoryData<GetElement> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.array_type.len() == 0 {
+            return f.write_str("[]");
+        }
+        writeln!(f, "[\n    // len = {:#x}", self.array_type.len())?;
+        for element_index in 0..self.array_type.len() {
+            let element = crate::util::BitSliceWriteWithBase(
+                self.get_element.get_element(element_index, self.array_type),
+            );
+            writeln!(f, "    [{element_index:#x}]: {element:#x},")?;
+        }
+        f.write_str("]")
+    }
+}
--- a/crates/fayalite/src/module.rs
+++ b/crates/fayalite/src/module.rs
--- a/crates/fayalite/src/module/transform.rs
+++ b/crates/fayalite/src/module/transform.rs
@ -1,5 +1,6 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
+pub mod deduce_resets;
 pub mod simplify_enums;
 pub mod simplify_memories;
 pub mod visit;
--- a/crates/fayalite/src/module/transform/deduce_resets.rs
+++ b/crates/fayalite/src/module/transform/deduce_resets.rs
--- a/crates/fayalite/src/module/transform/simplify_enums.rs
+++ b/crates/fayalite/src/module/transform/simplify_enums.rs
--- a/crates/fayalite/src/module/transform/simplify_memories.rs
+++ b/crates/fayalite/src/module/transform/simplify_memories.rs
@ -2,25 +2,24 @@
 // See Notices.txt for copyright information
 use crate::{
    annotations::TargetedAnnotation,
-    array::{Array, ArrayType, ValueArrayOrSlice},
-    bundle::{BundleType, BundleValue, DynBundle},
-    expr::{Expr, ExprEnum, ToExpr},
-    int::{DynSInt, DynSIntType, DynUInt, DynUIntType},
+    array::Array,
+    bundle::{Bundle, BundleType},
+    expr::{CastBitsTo, CastToBits, Expr, ExprEnum, ToExpr},
+    int::{Bool, SInt, Size, UInt},
    intern::{Intern, Interned},
    memory::{Mem, MemPort, PortType},
    module::{
        transform::visit::{Fold, Folder},
-        Block, Module, NameId, NameIdGen, ScopedNameId, Stmt, StmtConnect, StmtWire,
+        Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtWire,
    },
    source_location::SourceLocation,
-    ty::{DynCanonicalValue, DynType, Type, TypeEnum},
-    type_deduction::HitUndeducedType,
-    util::MakeMutSlice,
+    ty::{CanonicalType, Type},
+    util::{HashMap, MakeMutSlice},
    wire::Wire,
 };
 use bitvec::{slice::BitSlice, vec::BitVec};
-use hashbrown::HashMap;
 use std::{
+    convert::Infallible,
    fmt::Write,
    ops::{Deref, DerefMut},
    rc::Rc,
@ -28,26 +27,31 @@ use std::{

 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 enum SingleType {
-    UInt(DynUIntType),
-    SInt(DynSIntType),
-    UIntArray(ArrayType<[DynUInt]>),
-    SIntArray(ArrayType<[DynSInt]>),
+    UInt(UInt),
+    SInt(SInt),
+    Bool(Bool),
+    UIntArray(Array<UInt>),
+    SIntArray(Array<SInt>),
+    BoolArray(Array<Bool>),
 }

 impl SingleType {
-    fn is_array_type(self, array_type: ArrayType<[DynCanonicalValue]>) -> bool {
+    fn is_array_type(self, array_type: Array) -> bool {
        match self {
-            SingleType::UInt(_) | SingleType::SInt(_) => false,
-            SingleType::UIntArray(ty) => ty.canonical() == array_type,
-            SingleType::SIntArray(ty) => ty.canonical() == array_type,
+            SingleType::UInt(_) | SingleType::SInt(_) | SingleType::Bool(_) => false,
+            SingleType::UIntArray(ty) => ty.as_dyn_array() == array_type,
+            SingleType::SIntArray(ty) => ty.as_dyn_array() == array_type,
+            SingleType::BoolArray(ty) => ty.as_dyn_array() == array_type,
        }
    }
    fn array_len(self) -> usize {
        match self {
            SingleType::UInt(_ty) => 1,
            SingleType::SInt(_ty) => 1,
+            SingleType::Bool(_ty) => 1,
            SingleType::UIntArray(ty) => ty.len(),
            SingleType::SIntArray(ty) => ty.len(),
+            SingleType::BoolArray(ty) => ty.len(),
        }
    }
 }
@ -57,8 +61,9 @@ enum MemSplit {
    Bundle {
        fields: Rc<[MemSplit]>,
    },
+    PhantomConst,
    Single {
-        output_mem: Option<Mem<[DynCanonicalValue]>>,
+        output_mem: Option<Mem>,
        element_type: SingleType,
        unchanged_element_type: bool,
    },
@ -71,6 +76,7 @@ impl MemSplit {
    fn mark_changed_element_type(self) -> Self {
        match self {
            MemSplit::Bundle { fields: _ } => self,
+            MemSplit::PhantomConst => self,
            MemSplit::Single {
                output_mem,
                element_type,
@ -83,17 +89,18 @@ impl MemSplit {
            MemSplit::Array { elements: _ } => self,
        }
    }
-    fn new(element_type: TypeEnum) -> Result<Self, HitUndeducedType> {
-        Ok(match element_type {
-            TypeEnum::BundleType(bundle_ty) => MemSplit::Bundle {
+    fn new(element_type: CanonicalType) -> Self {
+        match element_type {
+            CanonicalType::Bundle(bundle_ty) => MemSplit::Bundle {
                fields: bundle_ty
                    .fields()
                    .into_iter()
-                    .map(|field| Ok(Self::new(field.ty.type_enum())?.mark_changed_element_type()))
-                    .collect::<Result<_, _>>()?,
+                    .map(|field| Self::new(field.ty).mark_changed_element_type())
+                    .collect(),
            },
-            TypeEnum::ArrayType(ty) => {
-                let element = MemSplit::new(ty.element().type_enum())?;
+            CanonicalType::PhantomConst(_) => MemSplit::PhantomConst,
+            CanonicalType::Array(ty) => {
+                let element = MemSplit::new(ty.element());
                if let Self::Single {
                    output_mem: _,
                    element_type,
@ -103,7 +110,7 @@ impl MemSplit {
                    match element_type {
                        SingleType::UInt(element_type) => Self::Single {
                            output_mem: None,
-                            element_type: SingleType::UIntArray(ArrayType::new_slice(
+                            element_type: SingleType::UIntArray(Array::new_dyn(
                                element_type,
                                ty.len(),
                            )),
@ -111,7 +118,15 @@ impl MemSplit {
                        },
                        SingleType::SInt(element_type) => Self::Single {
                            output_mem: None,
-                            element_type: SingleType::SIntArray(ArrayType::new_slice(
+                            element_type: SingleType::SIntArray(Array::new_dyn(
+                                element_type,
+                                ty.len(),
+                            )),
+                            unchanged_element_type,
+                        },
+                        SingleType::Bool(element_type) => Self::Single {
+                            output_mem: None,
+                            element_type: SingleType::BoolArray(Array::new_dyn(
                                element_type,
                                ty.len(),
                            )),
@ -119,8 +134,8 @@ impl MemSplit {
                        },
                        SingleType::UIntArray(element_type) => Self::Single {
                            output_mem: None,
-                            element_type: SingleType::UIntArray(ArrayType::new_slice(
-                                *element_type.element(),
+                            element_type: SingleType::UIntArray(Array::new_dyn(
+                                element_type.element(),
                                ty.len()
                                    .checked_mul(element_type.len())
                                    .expect("memory element type can't be too big"),
@ -129,8 +144,18 @@ impl MemSplit {
                        },
                        SingleType::SIntArray(element_type) => Self::Single {
                            output_mem: None,
-                            element_type: SingleType::SIntArray(ArrayType::new_slice(
-                                *element_type.element(),
+                            element_type: SingleType::SIntArray(Array::new_dyn(
+                                element_type.element(),
+                                ty.len()
+                                    .checked_mul(element_type.len())
+                                    .expect("memory element type can't be too big"),
+                            )),
+                            unchanged_element_type: false,
+                        },
+                        SingleType::BoolArray(element_type) => Self::Single {
+                            output_mem: None,
+                            element_type: SingleType::BoolArray(Array::new_dyn(
+                                element_type.element(),
                                ty.len()
                                    .checked_mul(element_type.len())
                                    .expect("memory element type can't be too big"),
@ -145,27 +170,31 @@ impl MemSplit {
                    }
                }
            }
-            TypeEnum::UInt(ty) => Self::Single {
+            CanonicalType::UInt(ty) => Self::Single {
                output_mem: None,
                element_type: SingleType::UInt(ty),
                unchanged_element_type: true,
            },
-            TypeEnum::SInt(ty) => Self::Single {
+            CanonicalType::SInt(ty) => Self::Single {
                output_mem: None,
                element_type: SingleType::SInt(ty),
                unchanged_element_type: true,
            },
-            TypeEnum::EnumType(ty) => Self::Single {
+            CanonicalType::Bool(ty) => Self::Single {
                output_mem: None,
-                element_type: SingleType::UInt(DynUIntType::new(ty.bit_width()?)),
+                element_type: SingleType::Bool(ty),
+                unchanged_element_type: true,
+            },
+            CanonicalType::Enum(ty) => Self::Single {
+                output_mem: None,
+                element_type: SingleType::UInt(UInt::new_dyn(ty.type_properties().bit_width)),
                unchanged_element_type: false,
            },
-            TypeEnum::Clock(_)
-            | TypeEnum::AsyncReset(_)
-            | TypeEnum::SyncReset(_)
-            | TypeEnum::Reset(_) => unreachable!("memory element type is a storable type"),
-            TypeEnum::Deduce(_) => return Err(HitUndeducedType),
-        })
+            CanonicalType::Clock(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_) => unreachable!("memory element type is a storable type"),
+        }
    }
 }

@ -174,9 +203,9 @@ struct MemState {
 }

 struct SplitState<'a> {
-    wire_rdata: Box<[Option<Expr<DynCanonicalValue>>]>,
-    wire_wdata: Box<[Option<Expr<DynCanonicalValue>>]>,
-    wire_wmask: Box<[Option<Expr<DynCanonicalValue>>]>,
+    wire_rdata: Box<[Option<Expr<CanonicalType>>]>,
+    wire_wdata: Box<[Option<Expr<CanonicalType>>]>,
+    wire_wmask: Box<[Option<Expr<CanonicalType>>]>,
    initial_value: Option<Box<[&'a BitSlice]>>,
 }

@ -224,7 +253,7 @@ impl<'a> SplitStateStack<'a> {
    }
    fn push_map(
        &mut self,
-        mut wire_map: impl FnMut(Expr<DynCanonicalValue>) -> Expr<DynCanonicalValue>,
+        mut wire_map: impl FnMut(Expr<CanonicalType>) -> Expr<CanonicalType>,
        mut initial_value_element_map: impl FnMut(&BitSlice) -> &BitSlice,
    ) {
        let top_index = self.top_index + 1;
@ -261,10 +290,10 @@ impl<'a> SplitStateStack<'a> {

 struct SplitMemState<'a, 'b> {
    module_state: &'a mut ModuleState,
-    input_mem: Mem<[DynCanonicalValue]>,
-    output_mems: &'a mut Vec<Mem<[DynCanonicalValue]>>,
+    input_mem: Mem,
+    output_mems: &'a mut Vec<Mem>,
    output_stmts: &'a mut Vec<Stmt>,
-    element_type: TypeEnum,
+    element_type: CanonicalType,
    split: &'a mut MemSplit,
    mem_name_path: &'a mut String,
    split_state_stack: &'a mut SplitStateStack<'b>,
@ -272,11 +301,11 @@ struct SplitMemState<'a, 'b> {
 }

 impl SplitMemState<'_, '_> {
-    fn split_mem(self) -> Result<(), HitUndeducedType> {
+    fn split_mem(self) {
        let outer_mem_name_path_len = self.mem_name_path.len();
        match self.split {
            MemSplit::Bundle { fields } => {
-                let TypeEnum::BundleType(bundle_type) = self.element_type else {
+                let CanonicalType::Bundle(bundle_type) = self.element_type else {
                    unreachable!();
                };
                for ((field, field_offset), split) in bundle_type
@ -288,9 +317,11 @@ impl SplitMemState<'_, '_> {
                    self.mem_name_path.truncate(outer_mem_name_path_len);
                    self.mem_name_path.push('_');
                    self.mem_name_path.push_str(&field.name);
-                    let field_ty_bit_width = field.ty.bit_width()?;
+                    let field_ty_bit_width = field.ty.bit_width();
                    self.split_state_stack.push_map(
-                        |e: Expr<DynCanonicalValue>| e.with_type::<DynBundle>().field(&field.name),
+                        |e: Expr<CanonicalType>| {
+                            Expr::field(Expr::<Bundle>::from_canonical(e), &field.name)
+                        },
                        |initial_value_element| {
                            &initial_value_element[field_offset..][..field_ty_bit_width]
                        },
@ -300,16 +331,17 @@ impl SplitMemState<'_, '_> {
                        input_mem: self.input_mem,
                        output_mems: self.output_mems,
                        output_stmts: self.output_stmts,
-                        element_type: field.ty.type_enum(),
+                        element_type: field.ty,
                        split,
                        mem_name_path: self.mem_name_path,
                        split_state_stack: self.split_state_stack,
                        mem_state: self.mem_state,
                    }
-                    .split_mem()?;
+                    .split_mem();
                    self.split_state_stack.pop();
                }
            }
+            MemSplit::PhantomConst => {}
            MemSplit::Single {
                output_mem,
                element_type: single_type,
@ -322,14 +354,14 @@ impl SplitMemState<'_, '_> {
                    *single_type,
                    self.mem_name_path,
                    self.split_state_stack.top(),
-                )?;
+                );
                for (port, wire) in new_mem
                    .ports()
                    .into_iter()
                    .zip(self.mem_state.replacement_ports.iter())
                {
                    let port_expr = port.to_expr();
-                    let wire_expr = Expr::<DynBundle>::new_unchecked(*wire);
+                    let wire_expr = Expr::<Bundle>::from_canonical(wire.to_expr());
                    for name in [
                        Some("addr"),
                        Some("clk"),
@ -341,8 +373,8 @@ impl SplitMemState<'_, '_> {
                        };
                        self.output_stmts.push(
                            StmtConnect {
-                                lhs: port_expr.field(name),
-                                rhs: wire_expr.field(name),
+                                lhs: Expr::field(port_expr, name),
+                                rhs: Expr::field(wire_expr, name),
                                source_location: port.source_location(),
                            }
                            .into(),
@ -353,18 +385,16 @@ impl SplitMemState<'_, '_> {
                self.output_mems.push(new_mem);
            }
            MemSplit::Array { elements } => {
-                let TypeEnum::ArrayType(array_type) = self.element_type else {
+                let CanonicalType::Array(array_type) = self.element_type else {
                    unreachable!();
                };
-                let element_type = array_type.element().type_enum();
-                let element_bit_width = array_type.element().bit_width()?;
+                let element_type = array_type.element();
+                let element_bit_width = element_type.bit_width();
                for (index, split) in elements.make_mut_slice().iter_mut().enumerate() {
                    self.mem_name_path.truncate(outer_mem_name_path_len);
                    write!(self.mem_name_path, "_{index}").unwrap();
                    self.split_state_stack.push_map(
-                        |e: Expr<DynCanonicalValue>| {
-                            e.with_type::<Array<[DynCanonicalValue]>>()[index]
-                        },
+                        |e| Expr::<Array>::from_canonical(e)[index],
                        |initial_value_element| {
                            &initial_value_element[index * element_bit_width..][..element_bit_width]
                        },
@ -380,18 +410,16 @@ impl SplitMemState<'_, '_> {
                        split_state_stack: self.split_state_stack,
                        mem_state: self.mem_state,
                    }
-                    .split_mem()?;
+                    .split_mem();
                    self.split_state_stack.pop();
                }
            }
        }
-        Ok(())
    }
 }

 struct ModuleState {
-    output_module: Option<Interned<Module<DynBundle>>>,
-    name_id_gen: NameIdGen,
+    output_module: Option<Interned<Module<Bundle>>>,
    memories: HashMap<ScopedNameId, MemState>,
 }

@ -399,18 +427,18 @@ impl ModuleState {
    #[allow(clippy::too_many_arguments)]
    fn connect_split_mem_port_arrays(
        output_stmts: &mut Vec<Stmt>,
-        input_array_types: &[ArrayType<[DynCanonicalValue]>],
+        input_array_types: &[Array],
        memory_element_array_range_start: usize,
        memory_element_array_range_len: usize,
-        wire_rdata: Option<Expr<DynCanonicalValue>>,
-        wire_wdata: Option<Expr<DynCanonicalValue>>,
-        wire_wmask: Option<Expr<DynCanonicalValue>>,
-        port_rdata: Option<Expr<Array<[DynCanonicalValue]>>>,
-        port_wdata: Option<Expr<Array<[DynCanonicalValue]>>>,
-        port_wmask: Option<Expr<Array<[DynCanonicalValue]>>>,
-        connect_rdata: impl Copy + Fn(&mut Vec<Stmt>, Expr<DynCanonicalValue>, Expr<DynCanonicalValue>),
-        connect_wdata: impl Copy + Fn(&mut Vec<Stmt>, Expr<DynCanonicalValue>, Expr<DynCanonicalValue>),
-        connect_wmask: impl Copy + Fn(&mut Vec<Stmt>, Expr<DynCanonicalValue>, Expr<DynCanonicalValue>),
+        wire_rdata: Option<Expr<CanonicalType>>,
+        wire_wdata: Option<Expr<CanonicalType>>,
+        wire_wmask: Option<Expr<CanonicalType>>,
+        port_rdata: Option<Expr<Array>>,
+        port_wdata: Option<Expr<Array>>,
+        port_wmask: Option<Expr<Array>>,
+        connect_rdata: impl Copy + Fn(&mut Vec<Stmt>, Expr<CanonicalType>, Expr<CanonicalType>),
+        connect_wdata: impl Copy + Fn(&mut Vec<Stmt>, Expr<CanonicalType>, Expr<CanonicalType>),
+        connect_wmask: impl Copy + Fn(&mut Vec<Stmt>, Expr<CanonicalType>, Expr<CanonicalType>),
    ) {
        let Some((input_array_type, input_array_types_rest)) = input_array_types.split_first()
        else {
@ -432,8 +460,7 @@ impl ModuleState {
        assert_eq!(memory_element_array_range_len % input_array_type.len(), 0);
        let chunk_size = memory_element_array_range_len / input_array_type.len();
        for index in 0..input_array_type.len() {
-            let map =
-                |e: Expr<DynCanonicalValue>| e.with_type::<Array<[DynCanonicalValue]>>()[index];
+            let map = |e| Expr::<Array>::from_canonical(e)[index];
            let wire_rdata = wire_rdata.map(map);
            let wire_wdata = wire_wdata.map(map);
            let wire_wmask = wire_wmask.map(map);
@ -458,20 +485,20 @@ impl ModuleState {
    fn connect_split_mem_port(
        &mut self,
        output_stmts: &mut Vec<Stmt>,
-        mut input_element_type: TypeEnum,
+        mut input_element_type: CanonicalType,
        single_type: SingleType,
        source_location: SourceLocation,
-        wire_rdata: Option<Expr<DynCanonicalValue>>,
-        wire_wdata: Option<Expr<DynCanonicalValue>>,
-        wire_wmask: Option<Expr<DynCanonicalValue>>,
-        port_rdata: Option<Expr<DynCanonicalValue>>,
-        port_wdata: Option<Expr<DynCanonicalValue>>,
-        port_wmask: Option<Expr<DynCanonicalValue>>,
-    ) -> Result<(), HitUndeducedType> {
+        wire_rdata: Option<Expr<CanonicalType>>,
+        wire_wdata: Option<Expr<CanonicalType>>,
+        wire_wmask: Option<Expr<CanonicalType>>,
+        port_rdata: Option<Expr<CanonicalType>>,
+        port_wdata: Option<Expr<CanonicalType>>,
+        port_wmask: Option<Expr<CanonicalType>>,
+    ) {
        let mut input_array_types = vec![];
        let connect_read = |output_stmts: &mut Vec<Stmt>,
-                            wire_read: Expr<DynCanonicalValue>,
-                            port_read: Expr<DynCanonicalValue>| {
+                            wire_read: Expr<CanonicalType>,
+                            port_read: Expr<CanonicalType>| {
            output_stmts.push(
                StmtConnect {
                    lhs: wire_read,
@ -482,8 +509,8 @@ impl ModuleState {
            );
        };
        let connect_write = |output_stmts: &mut Vec<Stmt>,
-                             wire_write: Expr<DynCanonicalValue>,
-                             port_write: Expr<DynCanonicalValue>| {
+                             wire_write: Expr<CanonicalType>,
+                             port_write: Expr<CanonicalType>| {
            output_stmts.push(
                StmtConnect {
                    lhs: port_write,
@ -493,32 +520,34 @@ impl ModuleState {
                .into(),
            );
        };
-        let connect_read_enum =
-            |output_stmts: &mut Vec<Stmt>,
-             wire_read: Expr<DynCanonicalValue>,
-             port_read: Expr<DynCanonicalValue>| {
-                connect_read(
-                    output_stmts,
-                    wire_read,
-                    port_read
-                        .with_type::<DynUInt>()
-                        .cast_bits_to(wire_read.ty()),
-                );
-            };
+        let connect_read_enum = |output_stmts: &mut Vec<Stmt>,
+                                 wire_read: Expr<CanonicalType>,
+                                 port_read: Expr<CanonicalType>| {
+            connect_read(
+                output_stmts,
+                wire_read,
+                Expr::<UInt>::from_canonical(port_read).cast_bits_to(Expr::ty(wire_read)),
+            );
+        };
        let connect_write_enum =
            |output_stmts: &mut Vec<Stmt>,
-             wire_write: Expr<DynCanonicalValue>,
-             port_write: Expr<DynCanonicalValue>| {
+             wire_write: Expr<CanonicalType>,
+             port_write: Expr<CanonicalType>| {
                connect_write(
                    output_stmts,
-                    wire_write.cast_to_bits().to_canonical_dyn(),
+                    Expr::canonical(wire_write.cast_to_bits()),
                    port_write,
                );
            };
        loop {
            match input_element_type {
-                TypeEnum::BundleType(_) => unreachable!("bundle types are always split"),
-                TypeEnum::EnumType(_)
+                CanonicalType::Bundle(_) => {
+                    unreachable!("bundle types are always split")
+                }
+                CanonicalType::PhantomConst(_) => {
+                    unreachable!("PhantomConst are always removed")
+                }
+                CanonicalType::Enum(_)
                    if input_array_types
                        .first()
                        .map(|&v| single_type.is_array_type(v))
@ -534,7 +563,7 @@ impl ModuleState {
                        connect_write(output_stmts, wire_wmask, port_wmask);
                    }
                }
-                TypeEnum::EnumType(_) => Self::connect_split_mem_port_arrays(
+                CanonicalType::Enum(_) => Self::connect_split_mem_port_arrays(
                    output_stmts,
                    &input_array_types,
                    0,
@ -542,25 +571,19 @@ impl ModuleState {
                    wire_rdata,
                    wire_wdata,
                    wire_wmask,
-                    port_rdata.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
-                    port_wdata.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
-                    port_wmask.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
+                    port_rdata.map(Expr::from_canonical),
+                    port_wdata.map(Expr::from_canonical),
+                    port_wmask.map(Expr::from_canonical),
                    connect_read_enum,
                    connect_write_enum,
-                    connect_write_enum,
+                    connect_write,
                ),
-                TypeEnum::ArrayType(array_type) => {
+                CanonicalType::Array(array_type) => {
                    input_array_types.push(array_type);
-                    input_element_type = array_type.element().type_enum();
+                    input_element_type = array_type.element();
                    continue;
                }
-                TypeEnum::UInt(_) | TypeEnum::SInt(_)
+                CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_)
                    if input_array_types
                        .first()
                        .map(|&v| single_type.is_array_type(v))
@ -576,62 +599,56 @@ impl ModuleState {
                        connect_write(output_stmts, wire_wmask, port_wmask);
                    }
                }
-                TypeEnum::UInt(_) | TypeEnum::SInt(_) => Self::connect_split_mem_port_arrays(
-                    output_stmts,
-                    &input_array_types,
-                    0,
-                    single_type.array_len(),
-                    wire_rdata,
-                    wire_wdata,
-                    wire_wmask,
-                    port_rdata.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
-                    port_wdata.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
-                    port_wmask.map(|e: Expr<DynCanonicalValue>| {
-                        e.with_type::<Array<[DynCanonicalValue]>>()
-                    }),
-                    connect_read,
-                    connect_write,
-                    connect_write,
-                ),
-                TypeEnum::Clock(_)
-                | TypeEnum::AsyncReset(_)
-                | TypeEnum::SyncReset(_)
-                | TypeEnum::Reset(_) => unreachable!("memory element type is a storable type"),
-                TypeEnum::Deduce(_) => return Err(HitUndeducedType),
+                CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_) => {
+                    Self::connect_split_mem_port_arrays(
+                        output_stmts,
+                        &input_array_types,
+                        0,
+                        single_type.array_len(),
+                        wire_rdata,
+                        wire_wdata,
+                        wire_wmask,
+                        port_rdata.map(Expr::from_canonical),
+                        port_wdata.map(Expr::from_canonical),
+                        port_wmask.map(Expr::from_canonical),
+                        connect_read,
+                        connect_write,
+                        connect_write,
+                    )
+                }
+                CanonicalType::Clock(_)
+                | CanonicalType::AsyncReset(_)
+                | CanonicalType::SyncReset(_)
+                | CanonicalType::Reset(_) => unreachable!("memory element type is a storable type"),
            }
            break;
        }
-        Ok(())
    }
    fn create_split_mem(
        &mut self,
-        input_mem: Mem<[DynCanonicalValue]>,
+        input_mem: Mem,
        output_stmts: &mut Vec<Stmt>,
-        input_element_type: TypeEnum,
+        input_element_type: CanonicalType,
        single_type: SingleType,
        mem_name_path: &str,
        split_state: &SplitState<'_>,
-    ) -> Result<Mem<[DynCanonicalValue]>, HitUndeducedType> {
-        let mem_name = self.name_id_gen.gen(Intern::intern_owned(format!(
-            "{}{mem_name_path}",
-            input_mem.scoped_name().1 .0
-        )));
+    ) -> Mem {
+        let mem_name = NameId(
+            Intern::intern_owned(format!("{}{mem_name_path}", input_mem.scoped_name().1 .0)),
+            Id::new(),
+        );
        let mem_name = ScopedNameId(input_mem.scoped_name().0, mem_name);
        let output_element_type = match single_type {
-            SingleType::UInt(ty) => ty.canonical_dyn(),
-            SingleType::SInt(ty) => ty.canonical_dyn(),
-            SingleType::UIntArray(ty) => ty.canonical_dyn(),
-            SingleType::SIntArray(ty) => ty.canonical_dyn(),
+            SingleType::UInt(ty) => ty.canonical(),
+            SingleType::SInt(ty) => ty.canonical(),
+            SingleType::Bool(ty) => ty.canonical(),
+            SingleType::UIntArray(ty) => ty.canonical(),
+            SingleType::SIntArray(ty) => ty.canonical(),
+            SingleType::BoolArray(ty) => ty.canonical(),
        };
-        let output_array_type =
-            ArrayType::new_slice(output_element_type, input_mem.array_type().len());
-        let output_array_bit_width = output_array_type.bit_width()?;
+        let output_array_type = Array::new_dyn(output_element_type, input_mem.array_type().len());
        let initial_value = split_state.initial_value.as_ref().map(|initial_value| {
-            let mut bits = BitVec::with_capacity(output_array_bit_width);
+            let mut bits = BitVec::with_capacity(output_array_type.type_properties().bit_width);
            for element in initial_value.iter() {
                bits.extend_from_bitslice(element);
            }
@ -648,7 +665,6 @@ impl ModuleState {
                    port.addr_type(),
                    output_element_type,
                )
-                .intern_sized()
            })
            .collect();
        let output_mem = Mem::new_unchecked(
@ -681,15 +697,15 @@ impl ModuleState {
            let port_rdata = port
                .port_kind()
                .rdata_name()
-                .map(|name| port_expr.field(name));
+                .map(|name| Expr::field(port_expr, name));
            let port_wdata = port
                .port_kind()
                .wdata_name()
-                .map(|name| port_expr.field(name));
+                .map(|name| Expr::field(port_expr, name));
            let port_wmask = port
                .port_kind()
                .wmask_name()
-                .map(|name| port_expr.field(name));
+                .map(|name| Expr::field(port_expr, name));
            self.connect_split_mem_port(
                output_stmts,
                input_element_type,
@ -701,18 +717,18 @@ impl ModuleState {
                port_rdata,
                port_wdata,
                port_wmask,
-            )?;
+            );
        }
-        Ok(output_mem)
+        output_mem
    }
    fn process_mem(
        &mut self,
-        input_mem: Mem<[DynCanonicalValue]>,
-        output_mems: &mut Vec<Mem<[DynCanonicalValue]>>,
+        input_mem: Mem,
+        output_mems: &mut Vec<Mem>,
        output_stmts: &mut Vec<Stmt>,
-    ) -> Result<(), HitUndeducedType> {
-        let element_type = input_mem.array_type().element().type_enum();
-        let mut split = MemSplit::new(element_type)?;
+    ) {
+        let element_type = input_mem.array_type().element();
+        let mut split = MemSplit::new(element_type);
        let mem_state = match split {
            MemSplit::Single {
                ref mut output_mem,
@ -735,7 +751,8 @@ impl ModuleState {
                ..
            }
            | MemSplit::Bundle { .. }
-            | MemSplit::Array { .. } => {
+            | MemSplit::Array { .. }
+            | MemSplit::PhantomConst => {
                let mut replacement_ports = Vec::with_capacity(input_mem.ports().len());
                let mut wire_port_rdata = Vec::with_capacity(input_mem.ports().len());
                let mut wire_port_wdata = Vec::with_capacity(input_mem.ports().len());
@ -744,38 +761,39 @@ impl ModuleState {
                    let port_ty = port.ty();
                    let NameId(mem_name, _) = input_mem.scoped_name().1;
                    let port_name = port.port_name();
-                    let wire_name = self
-                        .name_id_gen
-                        .gen(Intern::intern_owned(format!("{mem_name}_{port_name}")));
+                    let wire_name = NameId(
+                        Intern::intern_owned(format!("{mem_name}_{port_name}")),
+                        Id::new(),
+                    );
                    let wire = Wire::new_unchecked(
                        ScopedNameId(input_mem.scoped_name().0, wire_name),
                        port.source_location(),
                        port_ty,
                    );
                    let wire_expr = wire.to_expr();
-                    let canonical_wire = wire.to_dyn_canonical_wire();
+                    let canonical_wire = wire.canonical();
                    output_stmts.push(
                        StmtWire {
                            annotations: Default::default(),
-                            wire: canonical_wire.clone(),
+                            wire: canonical_wire,
                        }
                        .into(),
                    );
-                    replacement_ports.push(ExprEnum::Wire(canonical_wire.intern_sized()));
+                    replacement_ports.push(ExprEnum::Wire(canonical_wire));
                    wire_port_rdata.push(
                        port.port_kind()
                            .rdata_name()
-                            .map(|name| wire_expr.field(name)),
+                            .map(|name| Expr::field(wire_expr, name)),
                    );
                    wire_port_wdata.push(
                        port.port_kind()
                            .wdata_name()
-                            .map(|name| wire_expr.field(name)),
+                            .map(|name| Expr::field(wire_expr, name)),
                    );
                    wire_port_wmask.push(
                        port.port_kind()
                            .wmask_name()
-                            .map(|name| wire_expr.field(name)),
+                            .map(|name| Expr::field(wire_expr, name)),
                    );
                }
                let mem_state = MemState {
@ -810,19 +828,18 @@ impl ModuleState {
                    ),
                    mem_state: &mem_state,
                }
-                .split_mem()?;
+                .split_mem();
                mem_state
            }
        };
        self.memories.insert(input_mem.scoped_name(), mem_state);
-        Ok(())
    }
 }

 #[derive(Default)]
 struct State {
-    modules: HashMap<Interned<Module<DynBundle>>, ModuleState>,
-    current_module: Option<Interned<Module<DynBundle>>>,
+    modules: HashMap<Interned<Module<Bundle>>, ModuleState>,
+    current_module: Option<Interned<Module<Bundle>>>,
 }

 impl State {
@ -834,11 +851,11 @@ impl State {

 struct PushedState<'a> {
    state: &'a mut State,
-    old_module: Option<Interned<Module<DynBundle>>>,
+    old_module: Option<Interned<Module<Bundle>>>,
 }

 impl<'a> PushedState<'a> {
-    fn push_module(state: &'a mut State, module: Interned<Module<DynBundle>>) -> Self {
+    fn push_module(state: &'a mut State, module: Interned<Module<Bundle>>) -> Self {
        let old_module = state.current_module.replace(module);
        Self { state, old_module }
    }
@ -864,12 +881,9 @@ impl DerefMut for PushedState<'_> {
 }

 impl Folder for State {
-    type Error = HitUndeducedType;
+    type Error = Infallible;

-    fn fold_module<T: BundleValue>(&mut self, v: Module<T>) -> Result<Module<T>, Self::Error>
-    where
-        T::Type: BundleType<Value = T>,
-    {
+    fn fold_module<T: BundleType>(&mut self, v: Module<T>) -> Result<Module<T>, Self::Error> {
        let module: Interned<_> = v.canonical().intern_sized();
        if let Some(module_state) = self.modules.get(&module) {
            return Ok(Module::from_canonical(
@ -882,8 +896,7 @@ impl Folder for State {
            module,
            ModuleState {
                output_module: None,
-                name_id_gen: NameIdGen::for_module(*module),
-                memories: HashMap::new(),
+                memories: HashMap::default(),
            },
        );
        let mut this = PushedState::push_module(self, module);
@ -892,10 +905,10 @@ impl Folder for State {
        Ok(Module::from_canonical(*module))
    }

-    fn fold_mem<VA: ValueArrayOrSlice + ?Sized>(
+    fn fold_mem<Element: Type, Len: Size>(
        &mut self,
-        _v: Mem<VA>,
-    ) -> Result<Mem<VA>, Self::Error> {
+        _v: Mem<Element, Len>,
+    ) -> Result<Mem<Element, Len>, Self::Error> {
        unreachable!()
    }

@ -908,11 +921,13 @@ impl Folder for State {
        let mut output_stmts = vec![];
        let module_state = self.module_state();
        for input_mem in input_mems {
-            module_state.process_mem(input_mem, &mut output_mems, &mut output_stmts)?;
-        }
-        for stmt in input_stmts {
-            output_stmts.push(stmt.fold(self)?);
+            module_state.process_mem(input_mem, &mut output_mems, &mut output_stmts);
        }
+        output_stmts.extend(
+            input_stmts
+                .into_iter()
+                .map(|stmt| stmt.fold(self).unwrap_or_else(|v| match v {})),
+        );
        Ok(Block {
            memories: Intern::intern_owned(output_mems),
            stmts: Intern::intern_owned(output_stmts),
@ -937,8 +952,8 @@ impl Folder for State {
    }
 }

-pub fn simplify_memories(
-    module: Interned<Module<DynBundle>>,
-) -> Result<Interned<Module<DynBundle>>, HitUndeducedType> {
-    module.fold(&mut State::default())
+pub fn simplify_memories(module: Interned<Module<Bundle>>) -> Interned<Module<Bundle>> {
+    module
+        .fold(&mut State::default())
+        .unwrap_or_else(|v| match v {})
 }
--- a/crates/fayalite/src/module/transform/visit.rs
+++ b/crates/fayalite/src/module/transform/visit.rs
@ -2,33 +2,38 @@
 // See Notices.txt for copyright information
 #![allow(clippy::multiple_bound_locations)]
 use crate::{
-    annotations::{Annotation, CustomFirrtlAnnotation, TargetedAnnotation},
-    array::{Array, ArrayType, ArrayTypeTrait, ValueArrayOrSlice},
-    bundle::{BundleType, BundleValue, DynBundle, DynBundleType, FieldType},
-    clock::{Clock, ClockType},
-    enum_::{DynEnum, DynEnumType, EnumType, EnumValue, VariantType},
+    annotations::{
+        Annotation, BlackBoxInlineAnnotation, BlackBoxPathAnnotation, CustomFirrtlAnnotation,
+        DocStringAnnotation, DontTouchAnnotation, SVAttributeAnnotation, TargetedAnnotation,
+    },
+    array::ArrayType,
+    bundle::{Bundle, BundleField, BundleType},
+    clock::Clock,
+    enum_::{Enum, EnumType, EnumVariant},
    expr::{
-        ops, Expr, ExprEnum, Literal, Target, TargetBase, TargetChild, TargetPathArrayElement,
-        TargetPathBundleField, TargetPathDynArrayElement, TargetPathElement, ToExpr,
-    },
-    int::{
-        DynInt, DynIntType, DynSInt, DynSIntType, DynUInt, DynUIntType, IntType, IntTypeTrait,
-        StaticOrDynIntType,
+        ops,
+        target::{
+            Target, TargetBase, TargetChild, TargetPathArrayElement, TargetPathBundleField,
+            TargetPathDynArrayElement, TargetPathElement,
+        },
+        Expr, ExprEnum,
    },
+    formal::FormalKind,
+    int::{Bool, SIntType, SIntValue, Size, UIntType, UIntValue},
    intern::{Intern, Interned},
    memory::{Mem, MemPort, PortKind, PortName, PortType, ReadUnderWrite},
    module::{
        AnnotatedModuleIO, Block, BlockId, ExternModuleBody, ExternModuleParameter,
        ExternModuleParameterValue, Instance, Module, ModuleBody, ModuleIO, NameId,
-        NormalModuleBody, ScopedNameId, Stmt, StmtConnect, StmtDeclaration, StmtIf, StmtInstance,
-        StmtMatch, StmtReg, StmtWire,
+        NormalModuleBody, ScopedNameId, Stmt, StmtConnect, StmtDeclaration, StmtFormal, StmtIf,
+        StmtInstance, StmtMatch, StmtReg, StmtWire,
    },
+    phantom_const::PhantomConst,
    reg::Reg,
-    reset::{AsyncReset, AsyncResetType, Reset, ResetType, SyncReset, SyncResetType},
+    reset::{AsyncReset, Reset, ResetType, SyncReset},
+    sim::ExternModuleSimulation,
    source_location::SourceLocation,
-    ty::{DynCanonicalType, DynCanonicalValue, DynType, Type, TypeEnum, Value, ValueEnum},
-    type_deduction::UndeducedType,
-    util::{ConstBool, GenericConstBool},
+    ty::{CanonicalType, Type},
    wire::Wire,
 };
 use num_bigint::{BigInt, BigUint};
@ -474,7 +479,4 @@ impl<T: ?Sized + Visit<State>, State: ?Sized + Visitor> Visit<State> for &'_ mut
    }
 }

-type InternedDynType = Interned<dyn DynType>;
-type InternedDynCanonicalType = Interned<dyn DynCanonicalType>;
-
 include!(concat!(env!("OUT_DIR"), "/visit.rs"));
--- a/crates/fayalite/src/phantom_const.rs
+++ b/crates/fayalite/src/phantom_const.rs
@ -0,0 +1,410 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    expr::{
+        ops::{ExprPartialEq, ExprPartialOrd},
+        Expr, ToExpr,
+    },
+    int::Bool,
+    intern::{Intern, Interned, InternedCompare, LazyInterned, LazyInternedTrait, Memoize},
+    sim::value::{SimValue, SimValuePartialEq, ToSimValue, ToSimValueWithType},
+    source_location::SourceLocation,
+    ty::{
+        impl_match_variant_as_self,
+        serde_impls::{SerdeCanonicalType, SerdePhantomConst},
+        CanonicalType, StaticType, Type, TypeProperties,
+    },
+};
+use bitvec::slice::BitSlice;
+use serde::{
+    de::{DeserializeOwned, Error},
+    Deserialize, Deserializer, Serialize, Serializer,
+};
+use std::{
+    any::Any,
+    fmt,
+    hash::{Hash, Hasher},
+    marker::PhantomData,
+    ops::Index,
+};
+
+#[derive(Clone)]
+pub struct PhantomConstCanonicalValue {
+    parsed: serde_json::Value,
+    serialized: Interned<str>,
+}
+
+impl PhantomConstCanonicalValue {
+    pub fn from_json_value(parsed: serde_json::Value) -> Self {
+        let serialized = Intern::intern_owned(
+            serde_json::to_string(&parsed)
+                .expect("conversion from json value to text shouldn't fail"),
+        );
+        Self { parsed, serialized }
+    }
+    pub fn as_json_value(&self) -> &serde_json::Value {
+        &self.parsed
+    }
+    pub fn as_str(&self) -> Interned<str> {
+        self.serialized
+    }
+}
+
+impl fmt::Debug for PhantomConstCanonicalValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.serialized)
+    }
+}
+
+impl fmt::Display for PhantomConstCanonicalValue {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.serialized)
+    }
+}
+
+impl PartialEq for PhantomConstCanonicalValue {
+    fn eq(&self, other: &Self) -> bool {
+        self.serialized == other.serialized
+    }
+}
+
+impl Eq for PhantomConstCanonicalValue {}
+
+impl Hash for PhantomConstCanonicalValue {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.serialized.hash(state);
+    }
+}
+
+impl Serialize for PhantomConstCanonicalValue {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        self.parsed.serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for PhantomConstCanonicalValue {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Ok(Self::from_json_value(serde_json::Value::deserialize(
+            deserializer,
+        )?))
+    }
+}
+
+pub trait PhantomConstValue: Intern + InternedCompare + Serialize + fmt::Debug {
+    fn deserialize_value<'de, D>(deserializer: D) -> Result<Interned<Self>, D::Error>
+    where
+        D: serde::Deserializer<'de>;
+}
+
+impl<T> PhantomConstValue for T
+where
+    T: ?Sized + Intern + InternedCompare + Serialize + fmt::Debug,
+    Interned<T>: DeserializeOwned,
+{
+    fn deserialize_value<'de, D>(deserializer: D) -> Result<Interned<Self>, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        <Interned<T> as Deserialize<'de>>::deserialize(deserializer)
+    }
+}
+
+/// Wrapper type that allows any Rust value to be smuggled as a HDL [`Type`].
+/// This only works for values that can be [serialized][Serialize] to and [deserialized][Deserialize] from [JSON][serde_json].
+pub struct PhantomConst<T: ?Sized + PhantomConstValue = PhantomConstCanonicalValue> {
+    value: LazyInterned<T>,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Default)]
+pub struct PhantomConstWithoutGenerics;
+
+#[allow(non_upper_case_globals)]
+pub const PhantomConst: PhantomConstWithoutGenerics = PhantomConstWithoutGenerics;
+
+impl<T: Type + PhantomConstValue> Index<T> for PhantomConstWithoutGenerics {
+    type Output = PhantomConst<T>;
+
+    fn index(&self, value: T) -> &Self::Output {
+        Interned::into_inner(PhantomConst::new(value.intern()).intern_sized())
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> fmt::Debug for PhantomConst<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("PhantomConst").field(&self.get()).finish()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Clone for PhantomConst<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Copy for PhantomConst<T> {}
+
+impl<T: ?Sized + PhantomConstValue> PartialEq for PhantomConst<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.get() == other.get()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Eq for PhantomConst<T> {}
+
+impl<T: ?Sized + PhantomConstValue> Hash for PhantomConst<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.get().hash(state);
+    }
+}
+
+struct PhantomConstCanonicalMemoize<T: ?Sized, const IS_FROM_CANONICAL: bool>(PhantomData<T>);
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Copy
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Clone
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Eq
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> PartialEq
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl<T: ?Sized, const IS_FROM_CANONICAL: bool> Hash
+    for PhantomConstCanonicalMemoize<T, IS_FROM_CANONICAL>
+{
+    fn hash<H: Hasher>(&self, _state: &mut H) {}
+}
+
+impl<T: ?Sized + PhantomConstValue> Memoize for PhantomConstCanonicalMemoize<T, false> {
+    type Input = Interned<T>;
+    type InputOwned = Interned<T>;
+    type Output = Interned<PhantomConstCanonicalValue>;
+
+    fn inner(self, input: &Self::Input) -> Self::Output {
+        Intern::intern_sized(PhantomConstCanonicalValue::from_json_value(
+            serde_json::to_value(input)
+                .expect("serialization failed when constructing a canonical PhantomConst"),
+        ))
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Memoize for PhantomConstCanonicalMemoize<T, true> {
+    type Input = Interned<PhantomConstCanonicalValue>;
+    type InputOwned = Interned<PhantomConstCanonicalValue>;
+    type Output = Interned<T>;
+
+    fn inner(self, input: &Self::Input) -> Self::Output {
+        PhantomConstValue::deserialize_value(input.as_json_value())
+            .expect("deserialization failed ")
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> PhantomConst<T> {
+    pub fn new(value: Interned<T>) -> Self {
+        Self {
+            value: LazyInterned::Interned(value),
+        }
+    }
+    pub const fn new_lazy(v: &'static dyn LazyInternedTrait<T>) -> Self {
+        Self {
+            value: LazyInterned::new_lazy(v),
+        }
+    }
+    pub fn get(self) -> Interned<T> {
+        self.value.interned()
+    }
+    pub fn type_properties(self) -> TypeProperties {
+        <()>::TYPE_PROPERTIES
+    }
+    pub fn can_connect(self, other: Self) -> bool {
+        self == other
+    }
+    pub fn canonical_phantom_const(self) -> PhantomConst {
+        if let Some(&retval) = <dyn Any>::downcast_ref::<PhantomConst>(&self) {
+            return retval;
+        }
+        <PhantomConst>::new(
+            PhantomConstCanonicalMemoize::<T, false>(PhantomData).get_owned(self.get()),
+        )
+    }
+    pub fn from_canonical_phantom_const(canonical_type: PhantomConst) -> Self {
+        if let Some(&retval) = <dyn Any>::downcast_ref::<Self>(&canonical_type) {
+            return retval;
+        }
+        Self::new(
+            PhantomConstCanonicalMemoize::<T, true>(PhantomData).get_owned(canonical_type.get()),
+        )
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Type for PhantomConst<T> {
+    type BaseType = PhantomConst;
+    type MaskType = ();
+    type SimValue = PhantomConst<T>;
+    impl_match_variant_as_self!();
+
+    fn mask_type(&self) -> Self::MaskType {
+        ()
+    }
+
+    fn canonical(&self) -> CanonicalType {
+        CanonicalType::PhantomConst(self.canonical_phantom_const())
+    }
+
+    fn from_canonical(canonical_type: CanonicalType) -> Self {
+        let CanonicalType::PhantomConst(phantom_const) = canonical_type else {
+            panic!("expected PhantomConst");
+        };
+        Self::from_canonical_phantom_const(phantom_const)
+    }
+
+    fn source_location() -> SourceLocation {
+        SourceLocation::builtin()
+    }
+
+    fn sim_value_from_bits(&self, bits: &BitSlice) -> Self::SimValue {
+        assert!(bits.is_empty());
+        *self
+    }
+
+    fn sim_value_clone_from_bits(&self, value: &mut Self::SimValue, bits: &BitSlice) {
+        assert!(bits.is_empty());
+        assert_eq!(*value, *self);
+    }
+
+    fn sim_value_to_bits(&self, value: &Self::SimValue, bits: &mut BitSlice) {
+        assert!(bits.is_empty());
+        assert_eq!(*value, *self);
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> Default for PhantomConst<T>
+where
+    Interned<T>: Default,
+{
+    fn default() -> Self {
+        Self::TYPE
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> StaticType for PhantomConst<T>
+where
+    Interned<T>: Default,
+{
+    const TYPE: Self = PhantomConst {
+        value: LazyInterned::new_lazy(&Interned::<T>::default),
+    };
+    const MASK_TYPE: Self::MaskType = ();
+    const TYPE_PROPERTIES: TypeProperties = <()>::TYPE_PROPERTIES;
+    const MASK_TYPE_PROPERTIES: TypeProperties = <()>::TYPE_PROPERTIES;
+}
+
+type SerdeType<T> = SerdeCanonicalType<CanonicalType, SerdePhantomConst<Interned<T>>>;
+
+impl<T: ?Sized + PhantomConstValue> Serialize for PhantomConst<T> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        SerdeType::<T>::PhantomConst(SerdePhantomConst(self.get())).serialize(serializer)
+    }
+}
+
+impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for PhantomConst<T> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        match SerdeType::<T>::deserialize(deserializer)? {
+            SerdeCanonicalType::PhantomConst(SerdePhantomConst(value)) => Ok(Self::new(value)),
+            ty => Err(Error::invalid_value(
+                serde::de::Unexpected::Other(ty.as_serde_unexpected_str()),
+                &"a PhantomConst",
+            )),
+        }
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprPartialEq<Self> for PhantomConst<T> {
+    fn cmp_eq(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+
+    fn cmp_ne(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ExprPartialOrd<Self> for PhantomConst<T> {
+    fn cmp_lt(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+
+    fn cmp_le(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+
+    fn cmp_gt(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        false.to_expr()
+    }
+
+    fn cmp_ge(lhs: Expr<Self>, rhs: Expr<Self>) -> Expr<Bool> {
+        assert_eq!(Expr::ty(lhs), Expr::ty(rhs));
+        true.to_expr()
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> SimValuePartialEq<Self> for PhantomConst<T> {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        assert_eq!(SimValue::ty(this), SimValue::ty(other));
+        true
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValue for PhantomConst<T> {
+    type Type = PhantomConst<T>;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_value(*self, *self)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValueWithType<PhantomConst<T>> for PhantomConst<T> {
+    fn to_sim_value_with_type(&self, ty: PhantomConst<T>) -> SimValue<PhantomConst<T>> {
+        SimValue::from_value(ty, *self)
+    }
+}
+
+impl<T: ?Sized + PhantomConstValue> ToSimValueWithType<CanonicalType> for PhantomConst<T> {
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_value(Self::from_canonical(ty), *self))
+    }
+}
--- a/crates/fayalite/src/prelude.rs
+++ b/crates/fayalite/src/prelude.rs
@ -0,0 +1,43 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+pub use crate::{
+    annotations::{
+        BlackBoxInlineAnnotation, BlackBoxPathAnnotation, CustomFirrtlAnnotation,
+        DocStringAnnotation, DontTouchAnnotation, SVAttributeAnnotation,
+    },
+    array::{Array, ArrayType},
+    bundle::Bundle,
+    cli::Cli,
+    clock::{Clock, ClockDomain, ToClock},
+    enum_::{Enum, HdlNone, HdlOption, HdlSome},
+    expr::{
+        repeat, CastBitsTo, CastTo, CastToBits, Expr, HdlPartialEq, HdlPartialOrd, MakeUninitExpr,
+        ReduceBits, ToExpr,
+    },
+    formal::{
+        all_const, all_seq, any_const, any_seq, formal_global_clock, formal_reset, hdl_assert,
+        hdl_assert_with_enable, hdl_assume, hdl_assume_with_enable, hdl_cover,
+        hdl_cover_with_enable, MakeFormalExpr,
+    },
+    hdl, hdl_module,
+    int::{Bool, DynSize, KnownSize, SInt, SIntType, SIntValue, Size, UInt, UIntType, UIntValue},
+    memory::{Mem, MemBuilder, ReadUnderWrite},
+    module::{
+        annotate, connect, connect_any, incomplete_wire, instance, memory, memory_array,
+        memory_with_init, reg_builder, wire, Instance, Module, ModuleBuilder,
+    },
+    phantom_const::PhantomConst,
+    reg::Reg,
+    reset::{AsyncReset, Reset, SyncReset, ToAsyncReset, ToReset, ToSyncReset},
+    sim::{
+        time::{SimDuration, SimInstant},
+        value::{SimValue, ToSimValue, ToSimValueWithType},
+        ExternModuleSimulationState, Simulation,
+    },
+    source_location::SourceLocation,
+    ty::{AsMask, CanonicalType, Type},
+    util::{ConstUsize, GenericConstUsize},
+    wire::Wire,
+    __,
+};
+pub use bitvec::{slice::BitSlice, vec::BitVec};
--- a/crates/fayalite/src/reg.rs
+++ b/crates/fayalite/src/reg.rs
@ -2,24 +2,25 @@
 // See Notices.txt for copyright information
 use crate::{
    clock::ClockDomain,
-    expr::{Expr, ExprTrait, Flow, ToExpr},
+    expr::{Expr, Flow},
    intern::Interned,
    module::{NameId, ScopedNameId},
+    reset::{Reset, ResetType},
    source_location::SourceLocation,
-    ty::{DynCanonicalType, DynType, Type},
+    ty::{CanonicalType, Type},
 };
 use std::fmt;

-#[derive(Clone, Eq, PartialEq, Hash)]
-pub struct Reg<T: Type> {
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+pub struct Reg<T: Type, R: ResetType = Reset> {
    name: ScopedNameId,
    source_location: SourceLocation,
    ty: T,
-    clock_domain: Expr<ClockDomain>,
-    init: Option<Expr<T::Value>>,
+    clock_domain: Expr<ClockDomain<R>>,
+    init: Option<Expr<T>>,
 }

-impl<T: Type + fmt::Debug> fmt::Debug for Reg<T> {
+impl<T: Type + fmt::Debug, R: ResetType> fmt::Debug for Reg<T, R> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let Self {
            name,
@ -37,20 +38,8 @@ impl<T: Type + fmt::Debug> fmt::Debug for Reg<T> {
    }
 }

-impl<T: Type> ToExpr for Reg<T> {
-    type Type = T;
-
-    fn ty(&self) -> Self::Type {
-        self.ty.clone()
-    }
-
-    fn to_expr(&self) -> Expr<<Self::Type as Type>::Value> {
-        Expr::new_unchecked(self.expr_enum())
-    }
-}
-
-impl<T: Type> Reg<T> {
-    pub fn canonical(&self) -> Reg<T::CanonicalType> {
+impl<T: Type, R: ResetType> Reg<T, R> {
+    pub fn canonical(&self) -> Reg<CanonicalType, R> {
        let Self {
            name,
            source_location,
@ -66,52 +55,20 @@ impl<T: Type> Reg<T> {
            init: init.map(Expr::canonical),
        }
    }
-    pub fn to_dyn_reg(&self) -> Reg<Interned<dyn DynType>> {
-        let Self {
-            name,
-            source_location,
-            ref ty,
-            clock_domain,
-            init,
-        } = *self;
-        Reg {
-            name,
-            source_location,
-            ty: ty.to_dyn(),
-            clock_domain,
-            init: init.map(Expr::to_dyn),
-        }
-    }
-    pub fn to_dyn_canonical_reg(&self) -> Reg<Interned<dyn DynCanonicalType>> {
-        let Self {
-            name,
-            source_location,
-            ref ty,
-            clock_domain,
-            init,
-        } = *self;
-        Reg {
-            name,
-            source_location,
-            ty: ty.canonical_dyn(),
-            clock_domain,
-            init: init.map(Expr::to_canonical_dyn),
-        }
-    }
    #[track_caller]
    pub fn new_unchecked(
        scoped_name: ScopedNameId,
        source_location: SourceLocation,
        ty: T,
-        clock_domain: Expr<ClockDomain>,
-        init: Option<Expr<T::Value>>,
+        clock_domain: Expr<ClockDomain<R>>,
+        init: Option<Expr<T>>,
    ) -> Self {
        assert!(
-            ty.is_storable().unwrap_or(true),
+            ty.canonical().is_storable(),
            "register type must be a storable type"
        );
        if let Some(init) = init {
-            assert_eq!(ty, init.ty(), "register's type must match init type");
+            assert_eq!(ty, Expr::ty(init), "register's type must match init type");
        }
        Self {
            name: scoped_name,
@ -121,6 +78,9 @@ impl<T: Type> Reg<T> {
            init,
        }
    }
+    pub fn ty(&self) -> T {
+        self.ty
+    }
    pub fn source_location(&self) -> SourceLocation {
        self.source_location
    }
@ -139,10 +99,10 @@ impl<T: Type> Reg<T> {
    pub fn scoped_name(&self) -> ScopedNameId {
        self.name
    }
-    pub fn clock_domain(&self) -> Expr<ClockDomain> {
+    pub fn clock_domain(&self) -> Expr<ClockDomain<R>> {
        self.clock_domain
    }
-    pub fn init(&self) -> Option<Expr<T::Value>> {
+    pub fn init(&self) -> Option<Expr<T>> {
        self.init
    }
    pub fn flow(&self) -> Flow {
--- a/crates/fayalite/src/reset.rs
+++ b/crates/fayalite/src/reset.rs
@ -1,366 +1,169 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    expr::{Expr, ToExpr},
-    int::{UInt, UIntType},
-    intern::Interned,
+    clock::Clock,
+    expr::{ops, Expr, ToExpr},
+    int::{Bool, SInt, UInt},
    source_location::SourceLocation,
-    ty::{
-        impl_match_values_as_self, CanonicalType, CanonicalTypeKind, CanonicalValue, Connect,
-        DynCanonicalType, StaticType, Type, TypeEnum, Value, ValueEnum,
-    },
-    type_deduction::{HitUndeducedType, UndeducedType},
-    util::interned_bit,
+    ty::{impl_match_variant_as_self, CanonicalType, StaticType, Type, TypeProperties},
 };
 use bitvec::slice::BitSlice;

-pub trait ResetTypeTrait: CanonicalType + StaticType<MaskType = UIntType<1>> {}
-
-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
-pub struct AsyncResetType;
-
-impl AsyncResetType {
-    pub const fn new() -> Self {
-        Self
-    }
+mod sealed {
+    pub trait ResetTypeSealed {}
 }

-impl Connect<UndeducedType> for AsyncResetType {}
-
-impl Type for AsyncResetType {
-    type Value = AsyncReset;
-    type CanonicalType = AsyncResetType;
-    type CanonicalValue = AsyncReset;
-    type MaskType = UIntType<1>;
-    type MaskValue = UInt<1>;
-
-    impl_match_values_as_self!();
-
-    fn mask_type(&self) -> Self::MaskType {
-        UIntType::new()
-    }
-
-    fn canonical(&self) -> Self::CanonicalType {
-        *self
-    }
-
-    fn source_location(&self) -> SourceLocation {
-        SourceLocation::builtin()
-    }
-
-    fn type_enum(&self) -> TypeEnum {
-        TypeEnum::AsyncReset(*self)
-    }
-
-    fn from_canonical_type(t: Self::CanonicalType) -> Self {
-        t
-    }
-
-    fn as_dyn_canonical_type_impl(this: &Self) -> Option<&dyn DynCanonicalType> {
-        Some(this)
-    }
+pub trait ResetType:
+    StaticType<MaskType = Bool>
+    + sealed::ResetTypeSealed
+    + ops::ExprCastTo<Bool>
+    + ops::ExprCastTo<Reset>
+    + ops::ExprCastTo<SyncReset>
+    + ops::ExprCastTo<AsyncReset>
+    + ops::ExprCastTo<Clock>
+    + ops::ExprCastTo<UInt<1>>
+    + ops::ExprCastTo<SInt<1>>
+    + ops::ExprCastTo<UInt>
+    + ops::ExprCastTo<SInt>
+{
+    fn dispatch<D: ResetTypeDispatch>(input: D::Input<Self>, dispatch: D) -> D::Output<Self>;
 }

-impl Connect<Self> for AsyncResetType {}
+pub trait ResetTypeDispatch: Sized {
+    type Input<T: ResetType>;
+    type Output<T: ResetType>;

-impl CanonicalType for AsyncResetType {
-    const CANONICAL_TYPE_KIND: CanonicalTypeKind = CanonicalTypeKind::AsyncReset;
+    fn reset(self, input: Self::Input<Reset>) -> Self::Output<Reset>;
+    fn sync_reset(self, input: Self::Input<SyncReset>) -> Self::Output<SyncReset>;
+    fn async_reset(self, input: Self::Input<AsyncReset>) -> Self::Output<AsyncReset>;
 }

-impl StaticType for AsyncResetType {
-    fn static_type() -> Self {
-        Self
-    }
-}
+macro_rules! reset_type {
+    ($name:ident, $(#[$impl_trait:ident])? $Trait:ident::$trait_fn:ident, $is_castable_from_bits:literal, $dispatch_fn:ident) => {
+        #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
+        pub struct $name;

-impl ResetTypeTrait for AsyncResetType {}
+        impl Type for $name {
+            type BaseType = $name;
+            type MaskType = Bool;
+            type SimValue = bool;

-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
-pub struct AsyncReset(pub bool);
+            impl_match_variant_as_self!();

-impl ToExpr for AsyncReset {
-    type Type = AsyncResetType;
+            fn mask_type(&self) -> Self::MaskType {
+                Bool
+            }

-    fn ty(&self) -> Self::Type {
-        AsyncResetType
-    }
+            fn canonical(&self) -> CanonicalType {
+                CanonicalType::$name(*self)
+            }

-    fn to_expr(&self) -> Expr<Self> {
-        Expr::from_value(self)
-    }
-}
+            fn source_location() -> SourceLocation {
+                SourceLocation::builtin()
+            }

-impl Value for AsyncReset {
-    fn to_canonical(&self) -> <Self::Type as Type>::CanonicalValue {
-        *self
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
+            fn from_canonical(canonical_type: CanonicalType) -> Self {
+                let CanonicalType::$name(retval) = canonical_type else {
+                    panic!("expected {}", stringify!($name));
+                };
+                retval
+            }

-impl CanonicalValue for AsyncReset {
-    fn value_enum_impl(this: &Self) -> ValueEnum {
-        ValueEnum::AsyncReset(*this)
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
+            fn sim_value_from_bits(&self, bits: &BitSlice) -> Self::SimValue {
+                assert_eq!(bits.len(), 1);
+                bits[0]
+            }

-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
-pub struct SyncResetType;
+            fn sim_value_clone_from_bits(&self, value: &mut Self::SimValue, bits: &BitSlice) {
+                assert_eq!(bits.len(), 1);
+                *value = bits[0];
+            }

-impl SyncResetType {
-    pub const fn new() -> Self {
-        Self
-    }
-}
-
-impl Connect<UndeducedType> for SyncResetType {}
-
-impl Type for SyncResetType {
-    type CanonicalType = SyncResetType;
-    type Value = SyncReset;
-    type CanonicalValue = SyncReset;
-    type MaskType = UIntType<1>;
-    type MaskValue = UInt<1>;
-
-    impl_match_values_as_self!();
-
-    fn mask_type(&self) -> Self::MaskType {
-        UIntType::new()
-    }
-
-    fn canonical(&self) -> Self::CanonicalType {
-        *self
-    }
-
-    fn source_location(&self) -> SourceLocation {
-        SourceLocation::builtin()
-    }
-
-    fn type_enum(&self) -> TypeEnum {
-        TypeEnum::SyncReset(*self)
-    }
-
-    fn from_canonical_type(t: Self::CanonicalType) -> Self {
-        t
-    }
-
-    fn as_dyn_canonical_type_impl(this: &Self) -> Option<&dyn DynCanonicalType> {
-        Some(this)
-    }
-}
-
-impl Connect<Self> for SyncResetType {}
-
-impl CanonicalType for SyncResetType {
-    const CANONICAL_TYPE_KIND: CanonicalTypeKind = CanonicalTypeKind::SyncReset;
-}
-
-impl StaticType for SyncResetType {
-    fn static_type() -> Self {
-        Self
-    }
-}
-
-impl ResetTypeTrait for SyncResetType {}
-
-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
-pub struct SyncReset(pub bool);
-
-impl ToExpr for SyncReset {
-    type Type = SyncResetType;
-
-    fn ty(&self) -> Self::Type {
-        SyncResetType
-    }
-
-    fn to_expr(&self) -> Expr<Self> {
-        Expr::from_value(self)
-    }
-}
-
-impl Value for SyncReset {
-    fn to_canonical(&self) -> <Self::Type as Type>::CanonicalValue {
-        *self
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
-
-impl CanonicalValue for SyncReset {
-    fn value_enum_impl(this: &Self) -> ValueEnum {
-        ValueEnum::SyncReset(*this)
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        Ok(interned_bit(this.0))
-    }
-}
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, Default)]
-pub struct ResetType;
-
-impl ResetType {
-    pub const fn new() -> Self {
-        Self
-    }
-}
-
-impl Connect<UndeducedType> for ResetType {}
-
-impl Type for ResetType {
-    type Value = Reset;
-    type CanonicalType = ResetType;
-    type CanonicalValue = Reset;
-    type MaskType = UIntType<1>;
-    type MaskValue = UInt<1>;
-
-    impl_match_values_as_self!();
-
-    fn mask_type(&self) -> Self::MaskType {
-        UIntType::new()
-    }
-
-    fn canonical(&self) -> Self::CanonicalType {
-        *self
-    }
-
-    fn source_location(&self) -> SourceLocation {
-        SourceLocation::builtin()
-    }
-
-    fn type_enum(&self) -> TypeEnum {
-        TypeEnum::Reset(*self)
-    }
-
-    fn from_canonical_type(t: Self::CanonicalType) -> Self {
-        t
-    }
-
-    fn as_dyn_canonical_type_impl(this: &Self) -> Option<&dyn DynCanonicalType> {
-        Some(this)
-    }
-}
-
-impl Connect<Self> for ResetType {}
-
-impl CanonicalType for ResetType {
-    const CANONICAL_TYPE_KIND: CanonicalTypeKind = CanonicalTypeKind::Reset;
-}
-
-impl StaticType for ResetType {
-    fn static_type() -> Self {
-        Self
-    }
-}
-
-impl ResetTypeTrait for ResetType {}
-
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
-pub enum Reset {}
-
-impl ToExpr for Reset {
-    type Type = ResetType;
-
-    fn ty(&self) -> Self::Type {
-        match *self {}
-    }
-
-    fn to_expr(&self) -> Expr<Self> {
-        Expr::from_value(self)
-    }
-}
-
-impl Value for Reset {
-    fn to_canonical(&self) -> <Self::Type as Type>::CanonicalValue {
-        *self
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        match *this {}
-    }
-}
-
-impl CanonicalValue for Reset {
-    fn value_enum_impl(this: &Self) -> ValueEnum {
-        ValueEnum::Reset(*this)
-    }
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        match *this {}
-    }
-}
-
-macro_rules! make_to_reset {
-    (
-        $(#[from_value($from_value_ty:ty)])*
-        $vis:vis trait $Trait:ident {
-            fn $fn:ident(&self) -> Expr<$T:ty>;
+            fn sim_value_to_bits(&self, value: &Self::SimValue, bits: &mut BitSlice) {
+                assert_eq!(bits.len(), 1);
+                bits.set(0, *value);
+            }
        }
-    ) => {
-        $vis trait $Trait {
-            fn $fn(&self) -> Expr<$T>;
+
+        impl $name {
+            pub fn type_properties(self) -> TypeProperties {
+                Self::TYPE_PROPERTIES
+            }
+            pub fn can_connect(self, _rhs: Self) -> bool {
+                true
+            }
+        }
+
+        impl StaticType for $name {
+            const TYPE: Self = Self;
+            const MASK_TYPE: Self::MaskType = Bool;
+            const TYPE_PROPERTIES: TypeProperties = TypeProperties {
+                is_passive: true,
+                is_storable: false,
+                is_castable_from_bits: $is_castable_from_bits,
+                bit_width: 1,
+            };
+            const MASK_TYPE_PROPERTIES: TypeProperties = Bool::TYPE_PROPERTIES;
+        }
+
+        impl sealed::ResetTypeSealed for $name {}
+
+        impl ResetType for $name {
+            fn dispatch<D: ResetTypeDispatch>(
+                input: D::Input<Self>,
+                dispatch: D,
+            ) -> D::Output<Self> {
+                dispatch.$dispatch_fn(input)
+            }
+        }
+
+        pub trait $Trait {
+            fn $trait_fn(&self) -> Expr<$name>;
        }

        impl<T: ?Sized + $Trait> $Trait for &'_ T {
-            fn $fn(&self) -> Expr<$T> {
-                (**self).$fn()
+            fn $trait_fn(&self) -> Expr<$name> {
+                (**self).$trait_fn()
            }
        }

        impl<T: ?Sized + $Trait> $Trait for &'_ mut T {
-            fn $fn(&self) -> Expr<$T> {
-                (**self).$fn()
+            fn $trait_fn(&self) -> Expr<$name> {
+                (**self).$trait_fn()
            }
        }

        impl<T: ?Sized + $Trait> $Trait for Box<T> {
-            fn $fn(&self) -> Expr<$T> {
-                (**self).$fn()
+            fn $trait_fn(&self) -> Expr<$name> {
+                (**self).$trait_fn()
            }
        }

-        impl $Trait for Expr<$T> {
-            fn $fn(&self) -> Expr<$T> {
+        $($impl_trait $Trait for Expr<$name> {
+            fn $trait_fn(&self) -> Expr<$name> {
                *self
            }
-        }
-
-        impl $Trait for $T {
-            fn $fn(&self) -> Expr<$T> {
-                self.to_expr()
-            }
-        }
-
-        $(impl $Trait for $from_value_ty {
-            fn $fn(&self) -> Expr<$T> {
-                self.to_expr().$fn()
-            }
-        })*
+        })?
    };
 }

-make_to_reset! {
-    #[from_value(SyncReset)]
-    #[from_value(AsyncReset)]
-    pub trait ToReset {
-        fn to_reset(&self) -> Expr<Reset>;
+reset_type!(AsyncReset, #[impl] ToAsyncReset::to_async_reset, true, async_reset);
+reset_type!(SyncReset, #[impl] ToSyncReset::to_sync_reset, true, sync_reset);
+reset_type!(
+    Reset,
+    ToReset::to_reset,
+    false, // Reset is not castable from bits because we don't know if it's async or sync
+    reset
+);
+
+impl ToSyncReset for bool {
+    fn to_sync_reset(&self) -> Expr<SyncReset> {
+        self.to_expr().to_sync_reset()
    }
 }

-make_to_reset! {
-    #[from_value(bool)]
-    #[from_value(UInt<1>)]
-    pub trait ToAsyncReset {
-        fn to_async_reset(&self) -> Expr<AsyncReset>;
-    }
-}
-
-make_to_reset! {
-    #[from_value(bool)]
-    #[from_value(UInt<1>)]
-    pub trait ToSyncReset {
-        fn to_sync_reset(&self) -> Expr<SyncReset>;
+impl ToAsyncReset for bool {
+    fn to_async_reset(&self) -> Expr<AsyncReset> {
+        self.to_expr().to_async_reset()
    }
 }
--- a/crates/fayalite/src/sim.rs
+++ b/crates/fayalite/src/sim.rs
--- a/crates/fayalite/src/sim/interpreter.rs
+++ b/crates/fayalite/src/sim/interpreter.rs
--- a/crates/fayalite/src/sim/time.rs
+++ b/crates/fayalite/src/sim/time.rs
@ -0,0 +1,397 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use std::{
+    fmt,
+    ops::{Add, AddAssign, Sub, SubAssign},
+    time::Duration,
+};
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct SimInstant {
+    time_since_start: SimDuration,
+}
+
+impl SimInstant {
+    pub const fn checked_add(self, duration: SimDuration) -> Option<Self> {
+        let Some(time_since_start) = self.time_since_start.checked_add(duration) else {
+            return None;
+        };
+        Some(SimInstant { time_since_start })
+    }
+    pub const fn checked_duration_since(self, earlier: Self) -> Option<SimDuration> {
+        self.time_since_start.checked_sub(earlier.time_since_start)
+    }
+    pub const fn checked_sub(self, duration: SimDuration) -> Option<Self> {
+        let Some(time_since_start) = self.time_since_start.checked_sub(duration) else {
+            return None;
+        };
+        Some(SimInstant { time_since_start })
+    }
+    #[track_caller]
+    pub const fn duration_since(self, earlier: Self) -> SimDuration {
+        let Some(retval) = self.checked_duration_since(earlier) else {
+            panic!(
+                "tried to compute the duration since a later time -- durations can't be negative"
+            );
+        };
+        retval
+    }
+    pub const fn saturating_duration_since(self, earlier: Self) -> SimDuration {
+        let Some(retval) = self.checked_duration_since(earlier) else {
+            return SimDuration::ZERO;
+        };
+        retval
+    }
+}
+
+impl Add<SimDuration> for SimInstant {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn add(mut self, rhs: SimDuration) -> Self::Output {
+        self += rhs;
+        self
+    }
+}
+
+impl AddAssign<SimDuration> for SimInstant {
+    #[track_caller]
+    fn add_assign(&mut self, rhs: SimDuration) {
+        self.time_since_start += rhs;
+    }
+}
+
+impl Add<SimInstant> for SimDuration {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn add(self, rhs: SimInstant) -> Self::Output {
+        rhs.add(self)
+    }
+}
+
+impl Sub for SimInstant {
+    type Output = SimDuration;
+
+    #[track_caller]
+    fn sub(self, rhs: SimInstant) -> Self::Output {
+        self.duration_since(rhs)
+    }
+}
+
+impl Sub<SimDuration> for SimInstant {
+    type Output = SimInstant;
+
+    #[track_caller]
+    fn sub(self, rhs: SimDuration) -> Self::Output {
+        let Some(retval) = self.checked_sub(rhs) else {
+            panic!("SimInstant underflow");
+        };
+        retval
+    }
+}
+
+impl SubAssign<SimDuration> for SimInstant {
+    #[track_caller]
+    fn sub_assign(&mut self, rhs: SimDuration) {
+        *self = *self - rhs;
+    }
+}
+
+impl SimInstant {
+    pub const START: SimInstant = SimInstant {
+        time_since_start: SimDuration::ZERO,
+    };
+}
+
+impl fmt::Debug for SimInstant {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.time_since_start.fmt(f)
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct SimDuration {
+    attos: u128,
+}
+
+impl AddAssign for SimDuration {
+    #[track_caller]
+    fn add_assign(&mut self, rhs: SimDuration) {
+        *self = *self + rhs;
+    }
+}
+
+impl Add for SimDuration {
+    type Output = SimDuration;
+
+    #[track_caller]
+    fn add(self, rhs: SimDuration) -> Self::Output {
+        SimDuration {
+            attos: self
+                .attos
+                .checked_add(rhs.attos)
+                .expect("overflow adding durations"),
+        }
+    }
+}
+
+impl Sub for SimDuration {
+    type Output = Self;
+
+    #[track_caller]
+    fn sub(self, rhs: Self) -> Self::Output {
+        SimDuration {
+            attos: self
+                .attos
+                .checked_add(rhs.attos)
+                .expect("underflow subtracting durations -- durations can't be negative"),
+        }
+    }
+}
+
+impl SubAssign for SimDuration {
+    #[track_caller]
+    fn sub_assign(&mut self, rhs: Self) {
+        *self = *self - rhs;
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Default)]
+pub struct SimDurationParts {
+    pub attos: u16,
+    pub femtos: u16,
+    pub picos: u16,
+    pub nanos: u16,
+    pub micros: u16,
+    pub millis: u16,
+    pub secs: u128,
+}
+
+macro_rules! impl_duration_units {
+    (
+        $(
+            #[unit_const = $UNIT:ident, from_units = $from_units:ident, as_units = $as_units:ident, units = $units:ident, suffix = $suffix:literal]
+            const $log10_units_per_sec:ident: u32 = $log10_units_per_sec_value:expr;
+        )*
+    ) => {
+        impl SimDuration {
+            $(
+                const $log10_units_per_sec: u32 = $log10_units_per_sec_value;
+                pub const fn $from_units($units: u128) -> Self {
+                    Self::from_units_helper::<{ Self::$log10_units_per_sec }>($units)
+                }
+                pub const fn $as_units(self) -> u128 {
+                    self.attos / const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) }
+                }
+            )*
+            pub const fn to_parts(mut self) -> SimDurationParts {
+                $(
+                    let $units = self.attos / const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                    self.attos %= const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                )*
+                SimDurationParts {
+                    $($units: $units as _,)*
+                }
+            }
+            pub const fn from_parts_checked(parts: SimDurationParts) -> Option<Self> {
+                let attos = 0u128;
+                $(
+                    let Some(product) = const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) }.checked_mul(parts.$units as u128) else {
+                        return None;
+                    };
+                    let Some(attos) = attos.checked_add(product) else {
+                        return None;
+                    };
+                )*
+                Some(Self {
+                    attos,
+                })
+            }
+        }
+
+        impl fmt::Debug for SimDuration {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let ilog10_attos = match self.attos.checked_ilog10() {
+                    Some(v) => v,
+                    None => Self::LOG10_ATTOS_PER_SEC,
+                };
+                let (suffix, int, fraction, fraction_digits) =
+                    match Self::LOG10_ATTOS_PER_SEC.saturating_sub(ilog10_attos) {
+                    $(
+                        ..=Self::$log10_units_per_sec => {
+                            let divisor = const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) };
+                            (
+                                $suffix,
+                                self.attos / divisor,
+                                self.attos % divisor,
+                                (Self::LOG10_ATTOS_PER_SEC - Self::$log10_units_per_sec) as usize,
+                            )
+                        },
+                    )*
+                    _ => unreachable!(),
+                };
+                write!(f, "{int}")?;
+                if fraction != 0 {
+                    write!(f, ".{fraction:0fraction_digits$}")?;
+                }
+                write!(f, " {suffix}")
+            }
+        }
+
+        #[cfg(test)]
+        #[test]
+        fn test_duration_debug() {
+            $(
+                assert_eq!(
+                    format!("{:?}", SimDuration::$from_units(123)),
+                    concat!("123 ", $suffix)
+                );
+                assert_eq!(
+                    format!("{:?}", SimDuration::$from_units(1)),
+                    concat!("1 ", $suffix),
+                );
+                let mut v = SimDuration::$from_units(1);
+                if v.attos < 1 << 53 {
+                    v.attos += 1;
+                    assert_eq!(
+                        format!("{v:?}"),
+                        format!("{} {}", v.attos as f64 / 10.0f64.powf((SimDuration::LOG10_ATTOS_PER_SEC - SimDuration::$log10_units_per_sec) as f64), $suffix),
+                        "1 {} + 1 as == {} as", $suffix, v.attos,
+                    );
+                }
+            )*
+        }
+    };
+}
+
+impl_duration_units! {
+    #[unit_const = SECOND, from_units = from_secs, as_units = as_secs, units = secs, suffix = "s"]
+    const LOG10_SECS_PER_SEC: u32 = 0;
+    #[unit_const = MILLISECOND, from_units = from_millis, as_units = as_millis, units = millis, suffix = "ms"]
+    const LOG10_MILLIS_PER_SEC: u32 = 3;
+    #[unit_const = MICROSECOND, from_units = from_micros, as_units = as_micros, units = micros, suffix = "μs"]
+    const LOG10_MICROS_PER_SEC: u32 = 6;
+    #[unit_const = NANOSECOND, from_units = from_nanos, as_units = as_nanos, units = nanos, suffix = "ns"]
+    const LOG10_NANOS_PER_SEC: u32 = 9;
+    #[unit_const = PICOSECOND, from_units = from_picos, as_units = as_picos, units = picos, suffix = "ps"]
+    const LOG10_PICOS_PER_SEC: u32 = 12;
+    #[unit_const = FEMTOSECOND, from_units = from_femtos, as_units = as_femtos, units = femtos, suffix = "fs"]
+    const LOG10_FEMTOS_PER_SEC: u32 = 15;
+    #[unit_const = ATTOSECOND, from_units = from_attos, as_units = as_attos, units = attos, suffix = "as"]
+    const LOG10_ATTOS_PER_SEC: u32 = 18;
+}
+
+impl SimDuration {
+    const fn from_units_helper<const UNITS_PER_SEC: u32>(units: u128) -> Self {
+        let Some(attos) =
+            units.checked_mul(const { 10u128.pow(Self::LOG10_ATTOS_PER_SEC - UNITS_PER_SEC) })
+        else {
+            panic!("duration too big");
+        };
+        Self { attos }
+    }
+    pub const ZERO: SimDuration = SimDuration::from_secs(0);
+    pub const fn from_parts(parts: SimDurationParts) -> Self {
+        match Self::from_parts_checked(parts) {
+            Some(v) => v,
+            None => panic!("duration too big"),
+        }
+    }
+    pub const fn abs_diff(self, other: Self) -> Self {
+        Self {
+            attos: self.attos.abs_diff(other.attos),
+        }
+    }
+    pub const fn checked_add(self, rhs: Self) -> Option<Self> {
+        let Some(attos) = self.attos.checked_add(rhs.attos) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
+        let Some(attos) = self.attos.checked_sub(rhs.attos) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    pub const fn is_zero(self) -> bool {
+        self.attos == 0
+    }
+    pub const fn saturating_add(self, rhs: Self) -> Self {
+        Self {
+            attos: self.attos.saturating_add(rhs.attos),
+        }
+    }
+    pub const fn saturating_sub(self, rhs: Self) -> Self {
+        Self {
+            attos: self.attos.saturating_sub(rhs.attos),
+        }
+    }
+    pub const fn checked_ilog10(self) -> Option<i32> {
+        let Some(ilog10_attos) = self.attos.checked_ilog10() else {
+            return None;
+        };
+        Some(ilog10_attos as i32 - Self::LOG10_ATTOS_PER_SEC as i32)
+    }
+    #[track_caller]
+    pub const fn ilog10(self) -> i32 {
+        let Some(retval) = self.checked_ilog10() else {
+            panic!("tried to take the ilog10 of 0");
+        };
+        retval
+    }
+    pub const fn checked_pow10(log10: i32, underflow_is_zero: bool) -> Option<Self> {
+        let Some(log10) = Self::LOG10_ATTOS_PER_SEC.checked_add_signed(log10) else {
+            return if log10 < 0 && underflow_is_zero {
+                Some(Self::ZERO)
+            } else {
+                None
+            };
+        };
+        let Some(attos) = 10u128.checked_pow(log10) else {
+            return None;
+        };
+        Some(Self { attos })
+    }
+    #[track_caller]
+    pub const fn pow10(log10: i32) -> Self {
+        let Some(retval) = Self::checked_pow10(log10, true) else {
+            panic!("pow10 overflowed");
+        };
+        retval
+    }
+    pub const fn is_power_of_ten(self) -> bool {
+        const TEN: u128 = 10;
+        const NUMBER_OF_POWERS_OF_TEN: usize = {
+            let mut n = 0;
+            while let Some(_) = TEN.checked_pow(n as u32) {
+                n += 1;
+            }
+            n
+        };
+        const POWERS_OF_TEN: [u128; NUMBER_OF_POWERS_OF_TEN] = {
+            let mut retval = [0; NUMBER_OF_POWERS_OF_TEN];
+            let mut i = 0;
+            while i < NUMBER_OF_POWERS_OF_TEN {
+                retval[i] = TEN.pow(i as u32);
+                i += 1;
+            }
+            retval
+        };
+        let mut i = 0;
+        while i < NUMBER_OF_POWERS_OF_TEN {
+            if self.attos == POWERS_OF_TEN[i] {
+                return true;
+            }
+            i += 1;
+        }
+        false
+    }
+}
+
+impl From<Duration> for SimDuration {
+    fn from(duration: Duration) -> Self {
+        Self::from_nanos(duration.as_nanos())
+    }
+}
--- a/crates/fayalite/src/sim/value.rs
+++ b/crates/fayalite/src/sim/value.rs
@ -0,0 +1,913 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    array::{Array, ArrayType},
+    bundle::{Bundle, BundleType},
+    clock::Clock,
+    enum_::{Enum, EnumType},
+    expr::{CastBitsTo, Expr, ToExpr},
+    int::{Bool, IntType, KnownSize, SInt, SIntType, SIntValue, Size, UInt, UIntType, UIntValue},
+    reset::{AsyncReset, Reset, SyncReset},
+    ty::{CanonicalType, StaticType, Type},
+    util::{
+        alternating_cell::{AlternatingCell, AlternatingCellMethods},
+        ConstUsize,
+    },
+};
+use bitvec::{slice::BitSlice, vec::BitVec};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::{
+    fmt,
+    ops::{Deref, DerefMut},
+    sync::Arc,
+};
+
+#[derive(Copy, Clone, Eq, PartialEq)]
+enum ValidFlags {
+    BothValid = 0,
+    OnlyValueValid = 1,
+    OnlyBitsValid = 2,
+}
+
+#[derive(Clone)]
+struct SimValueInner<T: Type> {
+    value: T::SimValue,
+    bits: UIntValue,
+    valid_flags: ValidFlags,
+    ty: T,
+}
+
+impl<T: Type> SimValueInner<T> {
+    fn fill_bits(&mut self) {
+        match self.valid_flags {
+            ValidFlags::BothValid | ValidFlags::OnlyBitsValid => {}
+            ValidFlags::OnlyValueValid => {
+                self.ty.sim_value_to_bits(&self.value, self.bits.bits_mut());
+                self.valid_flags = ValidFlags::BothValid;
+            }
+        }
+    }
+    fn into_bits(mut self) -> UIntValue {
+        self.fill_bits();
+        self.bits
+    }
+    fn bits_mut(&mut self) -> &mut UIntValue {
+        self.fill_bits();
+        self.valid_flags = ValidFlags::OnlyBitsValid;
+        &mut self.bits
+    }
+    fn fill_value(&mut self) {
+        match self.valid_flags {
+            ValidFlags::BothValid | ValidFlags::OnlyValueValid => {}
+            ValidFlags::OnlyBitsValid => {
+                self.ty
+                    .sim_value_clone_from_bits(&mut self.value, self.bits.bits());
+                self.valid_flags = ValidFlags::BothValid;
+            }
+        }
+    }
+    fn into_value(mut self) -> T::SimValue {
+        self.fill_value();
+        self.value
+    }
+    fn value_mut(&mut self) -> &mut T::SimValue {
+        self.fill_value();
+        self.valid_flags = ValidFlags::OnlyValueValid;
+        &mut self.value
+    }
+}
+
+impl<T: Type> AlternatingCellMethods for SimValueInner<T> {
+    fn unique_to_shared(&mut self) {
+        match self.valid_flags {
+            ValidFlags::BothValid => return,
+            ValidFlags::OnlyValueValid => {
+                self.ty.sim_value_to_bits(&self.value, self.bits.bits_mut())
+            }
+            ValidFlags::OnlyBitsValid => self
+                .ty
+                .sim_value_clone_from_bits(&mut self.value, self.bits.bits()),
+        }
+        self.valid_flags = ValidFlags::BothValid;
+    }
+
+    fn shared_to_unique(&mut self) {}
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename = "SimValue")]
+#[serde(bound(
+    serialize = "T: Type<SimValue: Serialize> + Serialize",
+    deserialize = "T: Type<SimValue: Deserialize<'de>> + Deserialize<'de>"
+))]
+struct SerdeSimValue<'a, T: Type> {
+    ty: T,
+    value: std::borrow::Cow<'a, T::SimValue>,
+}
+
+impl<T: Type<SimValue: Serialize> + Serialize> Serialize for SimValue<T> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        SerdeSimValue {
+            ty: SimValue::ty(self),
+            value: std::borrow::Cow::Borrowed(&*self),
+        }
+        .serialize(serializer)
+    }
+}
+
+impl<'de, T: Type<SimValue: Deserialize<'de>> + Deserialize<'de>> Deserialize<'de> for SimValue<T> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let SerdeSimValue { ty, value } = SerdeSimValue::<T>::deserialize(deserializer)?;
+        Ok(SimValue::from_value(ty, value.into_owned()))
+    }
+}
+
+pub struct SimValue<T: Type> {
+    inner: AlternatingCell<SimValueInner<T>>,
+}
+
+impl<T: Type + Clone> Clone for SimValue<T> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: AlternatingCell::new_unique(self.inner.share().clone()),
+        }
+    }
+}
+
+impl<T: Type> SimValue<T> {
+    #[track_caller]
+    pub fn from_bits(ty: T, bits: UIntValue) -> Self {
+        assert_eq!(ty.canonical().bit_width(), bits.width());
+        let inner = SimValueInner {
+            value: ty.sim_value_from_bits(bits.bits()),
+            bits,
+            valid_flags: ValidFlags::BothValid,
+            ty,
+        };
+        Self {
+            inner: AlternatingCell::new_shared(inner),
+        }
+    }
+    #[track_caller]
+    pub fn from_bitslice(ty: T, bits: &BitSlice) -> Self {
+        Self::from_bits(ty, UIntValue::new(Arc::new(bits.to_bitvec())))
+    }
+    pub fn from_value(ty: T, value: T::SimValue) -> Self {
+        let inner = SimValueInner {
+            bits: UIntValue::new_dyn(Arc::new(BitVec::repeat(false, ty.canonical().bit_width()))),
+            value,
+            valid_flags: ValidFlags::OnlyValueValid,
+            ty,
+        };
+        Self {
+            inner: AlternatingCell::new_unique(inner),
+        }
+    }
+    pub fn ty(this: &Self) -> T {
+        this.inner.share().ty
+    }
+    pub fn into_bits(this: Self) -> UIntValue {
+        this.inner.into_inner().into_bits()
+    }
+    pub fn into_ty_and_bits(this: Self) -> (T, UIntValue) {
+        let inner = this.inner.into_inner();
+        (inner.ty, inner.into_bits())
+    }
+    pub fn bits(this: &Self) -> &UIntValue {
+        &this.inner.share().bits
+    }
+    pub fn bits_mut(this: &mut Self) -> &mut UIntValue {
+        this.inner.unique().bits_mut()
+    }
+    pub fn into_value(this: Self) -> T::SimValue {
+        this.inner.into_inner().into_value()
+    }
+    pub fn value(this: &Self) -> &T::SimValue {
+        &this.inner.share().value
+    }
+    pub fn value_mut(this: &mut Self) -> &mut T::SimValue {
+        this.inner.unique().value_mut()
+    }
+    #[track_caller]
+    pub fn from_canonical(v: SimValue<CanonicalType>) -> Self {
+        let (ty, bits) = SimValue::into_ty_and_bits(v);
+        Self::from_bits(T::from_canonical(ty), bits)
+    }
+    pub fn into_canonical(this: Self) -> SimValue<CanonicalType> {
+        let (ty, bits) = Self::into_ty_and_bits(this);
+        SimValue::from_bits(ty.canonical(), bits)
+    }
+    pub fn canonical(this: &Self) -> SimValue<CanonicalType> {
+        SimValue::from_bits(Self::ty(this).canonical(), Self::bits(this).clone())
+    }
+    #[track_caller]
+    pub fn from_dyn_int(v: SimValue<T::Dyn>) -> Self
+    where
+        T: IntType,
+    {
+        let (ty, bits) = SimValue::into_ty_and_bits(v);
+        SimValue::from_bits(T::from_dyn_int(ty), bits)
+    }
+    pub fn into_dyn_int(this: Self) -> SimValue<T::Dyn>
+    where
+        T: IntType,
+    {
+        let (ty, bits) = Self::into_ty_and_bits(this);
+        SimValue::from_bits(ty.as_dyn_int(), bits)
+    }
+    pub fn to_dyn_int(this: &Self) -> SimValue<T::Dyn>
+    where
+        T: IntType,
+    {
+        SimValue::from_bits(Self::ty(this).as_dyn_int(), Self::bits(&this).clone())
+    }
+    #[track_caller]
+    pub fn from_bundle(v: SimValue<Bundle>) -> Self
+    where
+        T: BundleType,
+    {
+        let (ty, bits) = SimValue::into_ty_and_bits(v);
+        SimValue::from_bits(T::from_canonical(CanonicalType::Bundle(ty)), bits)
+    }
+    pub fn into_bundle(this: Self) -> SimValue<Bundle>
+    where
+        T: BundleType,
+    {
+        let (ty, bits) = Self::into_ty_and_bits(this);
+        SimValue::from_bits(Bundle::from_canonical(ty.canonical()), bits)
+    }
+    pub fn to_bundle(this: &Self) -> SimValue<Bundle>
+    where
+        T: BundleType,
+    {
+        SimValue::from_bits(
+            Bundle::from_canonical(Self::ty(this).canonical()),
+            Self::bits(&this).clone(),
+        )
+    }
+    #[track_caller]
+    pub fn from_enum(v: SimValue<Enum>) -> Self
+    where
+        T: EnumType,
+    {
+        let (ty, bits) = SimValue::into_ty_and_bits(v);
+        SimValue::from_bits(T::from_canonical(CanonicalType::Enum(ty)), bits)
+    }
+    pub fn into_enum(this: Self) -> SimValue<Enum>
+    where
+        T: EnumType,
+    {
+        let (ty, bits) = Self::into_ty_and_bits(this);
+        SimValue::from_bits(Enum::from_canonical(ty.canonical()), bits)
+    }
+    pub fn to_enum(this: &Self) -> SimValue<Enum>
+    where
+        T: EnumType,
+    {
+        SimValue::from_bits(
+            Enum::from_canonical(Self::ty(this).canonical()),
+            Self::bits(&this).clone(),
+        )
+    }
+}
+
+impl<T: Type> Deref for SimValue<T> {
+    type Target = T::SimValue;
+
+    fn deref(&self) -> &Self::Target {
+        Self::value(self)
+    }
+}
+
+impl<T: Type> DerefMut for SimValue<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        Self::value_mut(self)
+    }
+}
+
+impl<T: Type> fmt::Debug for SimValue<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let inner = self.inner.share();
+        f.debug_struct("SimValue")
+            .field("ty", &inner.ty)
+            .field("value", &inner.value)
+            .finish()
+    }
+}
+
+impl<T: Type> ToExpr for SimValue<T> {
+    type Type = T;
+
+    #[track_caller]
+    fn to_expr(&self) -> Expr<Self::Type> {
+        let inner = self.inner.share();
+        inner.bits.cast_bits_to(inner.ty)
+    }
+}
+
+pub trait SimValuePartialEq<T: Type = Self>: Type {
+    #[track_caller]
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<T>) -> bool;
+}
+
+impl<T: SimValuePartialEq<U>, U: Type> PartialEq<SimValue<U>> for SimValue<T> {
+    #[track_caller]
+    fn eq(&self, other: &SimValue<U>) -> bool {
+        T::sim_value_eq(self, other)
+    }
+}
+
+impl<Width: Size> SimValuePartialEq<Self> for UIntType<Width> {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        **this == **other
+    }
+}
+
+impl<Width: Size> SimValuePartialEq<Self> for SIntType<Width> {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Self>) -> bool {
+        **this == **other
+    }
+}
+
+impl SimValuePartialEq<Bool> for Bool {
+    fn sim_value_eq(this: &SimValue<Self>, other: &SimValue<Bool>) -> bool {
+        **this == **other
+    }
+}
+
+pub trait ToSimValue: ToSimValueWithType<<Self as ToSimValue>::Type> {
+    type Type: Type;
+
+    #[track_caller]
+    fn to_sim_value(&self) -> SimValue<Self::Type>;
+    #[track_caller]
+    fn into_sim_value(self) -> SimValue<Self::Type>
+    where
+        Self: Sized,
+    {
+        self.to_sim_value()
+    }
+    #[track_caller]
+    fn arc_into_sim_value(self: Arc<Self>) -> SimValue<Self::Type> {
+        self.to_sim_value()
+    }
+    #[track_caller]
+    fn arc_to_sim_value(self: &Arc<Self>) -> SimValue<Self::Type> {
+        self.to_sim_value()
+    }
+}
+
+pub trait ToSimValueWithType<T: Type> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T>;
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T>
+    where
+        Self: Sized,
+    {
+        self.to_sim_value_with_type(ty)
+    }
+    #[track_caller]
+    fn arc_into_sim_value_with_type(self: Arc<Self>, ty: T) -> SimValue<T> {
+        self.to_sim_value_with_type(ty)
+    }
+    #[track_caller]
+    fn arc_to_sim_value_with_type(self: &Arc<Self>, ty: T) -> SimValue<T> {
+        self.to_sim_value_with_type(ty)
+    }
+}
+
+macro_rules! forward_to_sim_value_with_type {
+    ([$($generics:tt)*] $ty:ty) => {
+        impl<$($generics)*> ToSimValueWithType<<Self as ToSimValue>::Type> for $ty {
+            fn to_sim_value_with_type(&self, ty: <Self as ToSimValue>::Type) -> SimValue<<Self as ToSimValue>::Type> {
+                let retval = Self::to_sim_value(self);
+                assert_eq!(SimValue::ty(&retval), ty);
+                retval
+            }
+            #[track_caller]
+            fn into_sim_value_with_type(self, ty: <Self as ToSimValue>::Type) -> SimValue<<Self as ToSimValue>::Type>
+            where
+                Self: Sized,
+            {
+                let retval = Self::into_sim_value(self);
+                assert_eq!(SimValue::ty(&retval), ty);
+                retval
+            }
+            #[track_caller]
+            fn arc_into_sim_value_with_type(self: Arc<Self>, ty: <Self as ToSimValue>::Type) -> SimValue<<Self as ToSimValue>::Type> {
+                let retval = Self::arc_into_sim_value(self);
+                assert_eq!(SimValue::ty(&retval), ty);
+                retval
+            }
+            #[track_caller]
+            fn arc_to_sim_value_with_type(self: &Arc<Self>, ty: <Self as ToSimValue>::Type) -> SimValue<<Self as ToSimValue>::Type> {
+                let retval = Self::arc_to_sim_value(self);
+                assert_eq!(SimValue::ty(&retval), ty);
+                retval
+            }
+        }
+    };
+}
+
+impl<T: Type> ToSimValue for SimValue<T> {
+    type Type = T;
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        self.clone()
+    }
+
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        self
+    }
+}
+
+forward_to_sim_value_with_type!([T: Type] SimValue<T>);
+
+impl<T: Type> ToSimValueWithType<T> for BitVec {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        self.clone().into_sim_value_with_type(ty)
+    }
+
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T> {
+        Arc::new(self).arc_into_sim_value_with_type(ty)
+    }
+
+    #[track_caller]
+    fn arc_into_sim_value_with_type(self: Arc<Self>, ty: T) -> SimValue<T> {
+        SimValue::from_bits(ty, UIntValue::new_dyn(self))
+    }
+
+    #[track_caller]
+    fn arc_to_sim_value_with_type(self: &Arc<Self>, ty: T) -> SimValue<T> {
+        SimValue::from_bits(ty, UIntValue::new_dyn(self.clone()))
+    }
+}
+
+impl<T: Type> ToSimValueWithType<T> for bitvec::boxed::BitBox {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        self.clone().into_sim_value_with_type(ty)
+    }
+
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T> {
+        self.into_bitvec().into_sim_value_with_type(ty)
+    }
+}
+
+impl<T: Type> ToSimValueWithType<T> for BitSlice {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        self.to_bitvec().into_sim_value_with_type(ty)
+    }
+}
+
+impl<This: ?Sized + ToSimValue> ToSimValue for &'_ This {
+    type Type = This::Type;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        This::to_sim_value(self)
+    }
+}
+
+impl<This: ?Sized + ToSimValueWithType<T>, T: Type> ToSimValueWithType<T> for &'_ This {
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        This::to_sim_value_with_type(self, ty)
+    }
+}
+
+impl<This: ?Sized + ToSimValue> ToSimValue for &'_ mut This {
+    type Type = This::Type;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        This::to_sim_value(self)
+    }
+}
+
+impl<This: ?Sized + ToSimValueWithType<T>, T: Type> ToSimValueWithType<T> for &'_ mut This {
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        This::to_sim_value_with_type(self, ty)
+    }
+}
+
+impl<This: ?Sized + ToSimValue> ToSimValue for Arc<This> {
+    type Type = This::Type;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        This::arc_to_sim_value(self)
+    }
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        This::arc_into_sim_value(self)
+    }
+}
+
+impl<This: ?Sized + ToSimValueWithType<T>, T: Type> ToSimValueWithType<T> for Arc<This> {
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        This::arc_to_sim_value_with_type(self, ty)
+    }
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T> {
+        This::arc_into_sim_value_with_type(self, ty)
+    }
+}
+
+impl<This: ?Sized + ToSimValue + Send + Sync + 'static> ToSimValue
+    for crate::intern::Interned<This>
+{
+    type Type = This::Type;
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        This::to_sim_value(self)
+    }
+}
+
+impl<This: ?Sized + ToSimValueWithType<T> + Send + Sync + 'static, T: Type> ToSimValueWithType<T>
+    for crate::intern::Interned<This>
+{
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        This::to_sim_value_with_type(self, ty)
+    }
+}
+
+impl<This: ToSimValue> ToSimValue for Box<This> {
+    type Type = This::Type;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        This::to_sim_value(self)
+    }
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        This::into_sim_value(*self)
+    }
+}
+
+impl<This: ToSimValueWithType<T>, T: Type> ToSimValueWithType<T> for Box<This> {
+    fn to_sim_value_with_type(&self, ty: T) -> SimValue<T> {
+        This::to_sim_value_with_type(self, ty)
+    }
+    fn into_sim_value_with_type(self, ty: T) -> SimValue<T> {
+        This::into_sim_value_with_type(*self, ty)
+    }
+}
+
+impl<T: Type, Len: Size> SimValue<ArrayType<T, Len>> {
+    #[track_caller]
+    pub fn from_array_elements<I: IntoIterator<Item: ToSimValueWithType<T>>>(
+        ty: ArrayType<T, Len>,
+        elements: I,
+    ) -> Self {
+        let element_ty = ty.element();
+        let elements = Vec::from_iter(
+            elements
+                .into_iter()
+                .map(|element| element.into_sim_value_with_type(element_ty)),
+        );
+        assert_eq!(elements.len(), ty.len());
+        SimValue::from_value(ty, elements.try_into().ok().expect("already checked len"))
+    }
+}
+
+impl<Element: ToSimValueWithType<T>, T: Type> ToSimValueWithType<Array<T>> for [Element] {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+}
+
+impl<Element: ToSimValue<Type: StaticType>> ToSimValue for [Element] {
+    type Type = Array<Element::Type>;
+
+    #[track_caller]
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(ArrayType::new_dyn(StaticType::TYPE, self.len()), self)
+    }
+}
+
+impl<Element: ToSimValueWithType<CanonicalType>> ToSimValueWithType<CanonicalType> for [Element] {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+}
+
+impl<Element: ToSimValueWithType<T>, T: Type, const N: usize> ToSimValueWithType<Array<T, N>>
+    for [Element; N]
+where
+    ConstUsize<N>: KnownSize,
+{
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Array<T, N>) -> SimValue<Array<T, N>> {
+        SimValue::from_array_elements(ty, self)
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: Array<T, N>) -> SimValue<Array<T, N>> {
+        SimValue::from_array_elements(ty, self)
+    }
+}
+
+impl<Element: ToSimValue<Type: StaticType>, const N: usize> ToSimValue for [Element; N]
+where
+    ConstUsize<N>: KnownSize,
+{
+    type Type = Array<Element::Type, N>;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(StaticType::TYPE, self)
+    }
+
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(StaticType::TYPE, self)
+    }
+}
+
+impl<Element: ToSimValueWithType<T>, T: Type, const N: usize> ToSimValueWithType<Array<T>>
+    for [Element; N]
+{
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+}
+
+impl<Element: ToSimValueWithType<CanonicalType>, const N: usize> ToSimValueWithType<CanonicalType>
+    for [Element; N]
+{
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+}
+
+impl<Element: ToSimValueWithType<T>, T: Type> ToSimValueWithType<Array<T>> for Vec<Element> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+}
+
+impl<Element: ToSimValue<Type: StaticType>> ToSimValue for Vec<Element> {
+    type Type = Array<Element::Type>;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(ArrayType::new_dyn(StaticType::TYPE, self.len()), self)
+    }
+
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(ArrayType::new_dyn(StaticType::TYPE, self.len()), self)
+    }
+}
+
+impl<Element: ToSimValueWithType<CanonicalType>> ToSimValueWithType<CanonicalType>
+    for Vec<Element>
+{
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+}
+
+impl<Element: ToSimValueWithType<T>, T: Type> ToSimValueWithType<Array<T>> for Box<[Element]> {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: Array<T>) -> SimValue<Array<T>> {
+        SimValue::from_array_elements(ty, self)
+    }
+}
+
+impl<Element: ToSimValue<Type: StaticType>> ToSimValue for Box<[Element]> {
+    type Type = Array<Element::Type>;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(ArrayType::new_dyn(StaticType::TYPE, self.len()), self)
+    }
+
+    fn into_sim_value(self) -> SimValue<Self::Type> {
+        SimValue::from_array_elements(ArrayType::new_dyn(StaticType::TYPE, self.len()), self)
+    }
+}
+
+impl<Element: ToSimValueWithType<CanonicalType>> ToSimValueWithType<CanonicalType>
+    for Box<[Element]>
+{
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+    #[track_caller]
+    fn into_sim_value_with_type(self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        SimValue::into_canonical(SimValue::from_array_elements(
+            <Array>::from_canonical(ty),
+            self,
+        ))
+    }
+}
+
+impl<T: Type> ToSimValue for Expr<T> {
+    type Type = T;
+    #[track_caller]
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_bitslice(
+            Expr::ty(*self),
+            &crate::expr::ToLiteralBits::to_literal_bits(self)
+                .expect("must be a literal expression"),
+        )
+    }
+}
+
+forward_to_sim_value_with_type!([T: Type] Expr<T>);
+
+macro_rules! impl_to_sim_value_for_bool_like {
+    ($ty:ident) => {
+        impl ToSimValueWithType<$ty> for bool {
+            fn to_sim_value_with_type(&self, ty: $ty) -> SimValue<$ty> {
+                SimValue::from_value(ty, *self)
+            }
+        }
+    };
+}
+
+impl ToSimValue for bool {
+    type Type = Bool;
+
+    fn to_sim_value(&self) -> SimValue<Self::Type> {
+        SimValue::from_value(Bool, *self)
+    }
+}
+
+impl_to_sim_value_for_bool_like!(Bool);
+impl_to_sim_value_for_bool_like!(AsyncReset);
+impl_to_sim_value_for_bool_like!(SyncReset);
+impl_to_sim_value_for_bool_like!(Reset);
+impl_to_sim_value_for_bool_like!(Clock);
+
+impl ToSimValueWithType<CanonicalType> for bool {
+    #[track_caller]
+    fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+        match ty {
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Array(_)
+            | CanonicalType::Enum(_)
+            | CanonicalType::Bundle(_)
+            | CanonicalType::PhantomConst(_) => {
+                panic!("can't create SimValue from bool: expected value of type: {ty:?}");
+            }
+            CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_) => {
+                SimValue::from_bits(ty, UIntValue::new(Arc::new(BitVec::repeat(*self, 1))))
+            }
+        }
+    }
+}
+
+macro_rules! impl_to_sim_value_for_primitive_int {
+    ($prim:ident) => {
+        impl ToSimValue for $prim {
+            type Type = <$prim as ToExpr>::Type;
+
+            #[track_caller]
+            fn to_sim_value(
+                &self,
+            ) -> SimValue<Self::Type> {
+                SimValue::from_value(StaticType::TYPE, (*self).into())
+            }
+        }
+
+        forward_to_sim_value_with_type!([] $prim);
+
+        impl ToSimValueWithType<<<$prim as ToExpr>::Type as IntType>::Dyn> for $prim {
+            #[track_caller]
+            fn to_sim_value_with_type(
+                &self,
+                ty: <<$prim as ToExpr>::Type as IntType>::Dyn,
+            ) -> SimValue<<<$prim as ToExpr>::Type as IntType>::Dyn> {
+                SimValue::from_value(
+                    ty,
+                    <<$prim as ToExpr>::Type as Type>::SimValue::from(*self).as_dyn_int(),
+                )
+            }
+        }
+
+        impl ToSimValueWithType<CanonicalType> for $prim {
+            #[track_caller]
+            fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+                let ty: <<$prim as ToExpr>::Type as IntType>::Dyn = Type::from_canonical(ty);
+                SimValue::into_canonical(self.to_sim_value_with_type(ty))
+            }
+        }
+    };
+}
+
+impl_to_sim_value_for_primitive_int!(u8);
+impl_to_sim_value_for_primitive_int!(u16);
+impl_to_sim_value_for_primitive_int!(u32);
+impl_to_sim_value_for_primitive_int!(u64);
+impl_to_sim_value_for_primitive_int!(u128);
+impl_to_sim_value_for_primitive_int!(usize);
+impl_to_sim_value_for_primitive_int!(i8);
+impl_to_sim_value_for_primitive_int!(i16);
+impl_to_sim_value_for_primitive_int!(i32);
+impl_to_sim_value_for_primitive_int!(i64);
+impl_to_sim_value_for_primitive_int!(i128);
+impl_to_sim_value_for_primitive_int!(isize);
+
+macro_rules! impl_to_sim_value_for_int_value {
+    ($IntValue:ident, $Int:ident, $IntType:ident) => {
+        impl<Width: Size> ToSimValue for $IntValue<Width> {
+            type Type = $IntType<Width>;
+
+            fn to_sim_value(&self) -> SimValue<Self::Type> {
+                SimValue::from_value(self.ty(), self.clone())
+            }
+
+            fn into_sim_value(self) -> SimValue<Self::Type> {
+                SimValue::from_value(self.ty(), self)
+            }
+        }
+
+        impl<Width: Size> ToSimValueWithType<$IntType<Width>> for $IntValue<Width> {
+            fn to_sim_value_with_type(&self, ty: $IntType<Width>) -> SimValue<$IntType<Width>> {
+                SimValue::from_value(ty, self.clone())
+            }
+
+            fn into_sim_value_with_type(self, ty: $IntType<Width>) -> SimValue<$IntType<Width>> {
+                SimValue::from_value(ty, self)
+            }
+        }
+
+        impl<Width: KnownSize> ToSimValueWithType<$Int> for $IntValue<Width> {
+            fn to_sim_value_with_type(&self, ty: $Int) -> SimValue<$Int> {
+                self.bits().to_sim_value_with_type(ty)
+            }
+
+            fn into_sim_value_with_type(self, ty: $Int) -> SimValue<$Int> {
+                self.into_bits().into_sim_value_with_type(ty)
+            }
+        }
+
+        impl<Width: Size> ToSimValueWithType<CanonicalType> for $IntValue<Width> {
+            #[track_caller]
+            fn to_sim_value_with_type(&self, ty: CanonicalType) -> SimValue<CanonicalType> {
+                SimValue::into_canonical(
+                    self.to_sim_value_with_type($IntType::<Width>::from_canonical(ty)),
+                )
+            }
+
+            #[track_caller]
+            fn into_sim_value_with_type(self, ty: CanonicalType) -> SimValue<CanonicalType> {
+                SimValue::into_canonical(
+                    self.into_sim_value_with_type($IntType::<Width>::from_canonical(ty)),
+                )
+            }
+        }
+    };
+}
+
+impl_to_sim_value_for_int_value!(UIntValue, UInt, UIntType);
+impl_to_sim_value_for_int_value!(SIntValue, SInt, SIntType);
--- a/crates/fayalite/src/sim/vcd.rs
+++ b/crates/fayalite/src/sim/vcd.rs
--- a/crates/fayalite/src/source_location.rs
+++ b/crates/fayalite/src/source_location.rs
@ -2,9 +2,8 @@
 // See Notices.txt for copyright information
 use crate::{
    intern::{Intern, Interned},
-    util::DebugAsDisplay,
+    util::{DebugAsDisplay, HashMap},
 };
-use hashbrown::HashMap;
 use std::{cell::RefCell, fmt, num::NonZeroUsize, panic, path::Path};

 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@ -97,7 +96,7 @@ impl NormalizeFilesForTestsState {
    fn new() -> Self {
        Self {
            test_position: panic::Location::caller(),
-            file_pattern_matches: HashMap::new(),
+            file_pattern_matches: HashMap::default(),
        }
    }
 }
@ -143,7 +142,7 @@ impl From<&'_ panic::Location<'_>> for SourceLocation {
                        map.entry_ref(file)
                            .or_insert_with(|| NormalizedFileForTestState {
                                file_name_id: NonZeroUsize::new(len + 1).unwrap(),
-                                positions_map: HashMap::new(),
+                                positions_map: HashMap::default(),
                            });
                    file_str = m.generate_file_name(file_state.file_name_id);
                    file = &file_str;
--- a/crates/fayalite/src/testing.rs
+++ b/crates/fayalite/src/testing.rs
@ -0,0 +1,122 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use crate::{
+    cli::{FormalArgs, FormalMode, FormalOutput, RunPhase},
+    firrtl::ExportOptions,
+    util::HashMap,
+};
+use clap::Parser;
+use serde::Deserialize;
+use std::{
+    fmt::Write,
+    path::{Path, PathBuf},
+    process::Command,
+    sync::{Mutex, OnceLock},
+};
+
+fn assert_formal_helper() -> FormalArgs {
+    static FORMAL_ARGS: OnceLock<FormalArgs> = OnceLock::new();
+    // ensure we only run parsing once, so errors from env vars don't produce overlapping output if we're called on multiple threads
+    FORMAL_ARGS
+        .get_or_init(|| FormalArgs::parse_from(["fayalite::testing::assert_formal"]))
+        .clone()
+}
+
+#[derive(Deserialize)]
+struct CargoMetadata {
+    target_directory: String,
+}
+
+fn get_cargo_target_dir() -> &'static Path {
+    static RETVAL: OnceLock<PathBuf> = OnceLock::new();
+    RETVAL.get_or_init(|| {
+        let output = Command::new(
+            std::env::var_os("CARGO")
+                .as_deref()
+                .unwrap_or("cargo".as_ref()),
+        )
+        .arg("metadata")
+        .output()
+        .expect("can't run `cargo metadata`");
+        if !output.status.success() {
+            panic!(
+                "can't run `cargo metadata`:\n{}\nexited with status: {}",
+                String::from_utf8_lossy(&output.stderr),
+                output.status
+            );
+        }
+        let CargoMetadata { target_directory } =
+            serde_json::from_slice(&output.stdout).expect("can't parse output of `cargo metadata`");
+        PathBuf::from(target_directory)
+    })
+}
+
+#[track_caller]
+fn get_assert_formal_target_path(test_name: &dyn std::fmt::Display) -> PathBuf {
+    static DIRS: Mutex<Option<HashMap<String, u64>>> = Mutex::new(None);
+    let test_name = test_name.to_string();
+    // don't use line/column numbers since that constantly changes as you edit tests
+    let file = std::panic::Location::caller().file();
+    // simple reproducible hash
+    let simple_hash = file.bytes().chain(test_name.bytes()).fold(
+        ((file.len() as u32) << 16).wrapping_add(test_name.len() as u32),
+        |mut h, b| {
+            h = h.wrapping_mul(0xaa0d184b);
+            h ^= h.rotate_right(5);
+            h ^= h.rotate_right(13);
+            h.wrapping_add(b as u32)
+        },
+    );
+    let mut dir = String::with_capacity(64);
+    for ch in Path::new(file)
+        .file_stem()
+        .unwrap_or_default()
+        .to_str()
+        .unwrap()
+        .chars()
+        .chain(['-'])
+        .chain(test_name.chars())
+    {
+        dir.push(match ch {
+            ch if ch.is_alphanumeric() => ch,
+            '_' | '-' | '+' | '.' | ',' | ' ' => ch,
+            _ => '_',
+        });
+    }
+    write!(dir, "-{simple_hash:08x}").unwrap();
+    let index = *DIRS
+        .lock()
+        .unwrap()
+        .get_or_insert_with(HashMap::default)
+        .entry_ref(&dir)
+        .and_modify(|v| *v += 1)
+        .or_insert(0);
+    write!(dir, "-{index}").unwrap();
+    get_cargo_target_dir()
+        .join("fayalite_assert_formal")
+        .join(dir)
+}
+
+#[track_caller]
+pub fn assert_formal<M>(
+    test_name: impl std::fmt::Display,
+    module: M,
+    mode: FormalMode,
+    depth: u64,
+    solver: Option<&str>,
+    export_options: ExportOptions,
+) where
+    FormalArgs: RunPhase<M, Output = FormalOutput>,
+{
+    let mut args = assert_formal_helper();
+    args.verilog.firrtl.base.redirect_output_for_rust_test = true;
+    args.verilog.firrtl.base.output = Some(get_assert_formal_target_path(&test_name));
+    args.verilog.firrtl.export_options = export_options;
+    args.verilog.debug = true;
+    args.mode = mode;
+    args.depth = depth;
+    if let Some(solver) = solver {
+        args.solver = solver.into();
+    }
+    args.run(module).expect("testing::assert_formal() failed");
+}
--- a/crates/fayalite/src/ty.rs
+++ b/crates/fayalite/src/ty.rs
--- a/crates/fayalite/src/ty/serde_impls.rs
+++ b/crates/fayalite/src/ty/serde_impls.rs
@ -0,0 +1,130 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    array::Array,
+    bundle::{Bundle, BundleType},
+    clock::Clock,
+    enum_::{Enum, EnumType},
+    int::{Bool, SInt, UInt},
+    intern::Interned,
+    phantom_const::{PhantomConstCanonicalValue, PhantomConstValue},
+    prelude::PhantomConst,
+    reset::{AsyncReset, Reset, SyncReset},
+    ty::{BaseType, CanonicalType},
+};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+pub(crate) struct SerdePhantomConst<T>(pub T);
+
+impl<T: ?Sized + PhantomConstValue> Serialize for SerdePhantomConst<Interned<T>> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.0.serialize(serializer)
+    }
+}
+
+impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for SerdePhantomConst<Interned<T>> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        T::deserialize_value(deserializer).map(Self)
+    }
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename = "CanonicalType")]
+pub(crate) enum SerdeCanonicalType<
+    ArrayElement = CanonicalType,
+    ThePhantomConst = SerdePhantomConst<Interned<PhantomConstCanonicalValue>>,
+> {
+    UInt {
+        width: usize,
+    },
+    SInt {
+        width: usize,
+    },
+    Bool,
+    Array {
+        element: ArrayElement,
+        len: usize,
+    },
+    Enum {
+        variants: Interned<[crate::enum_::EnumVariant]>,
+    },
+    Bundle {
+        fields: Interned<[crate::bundle::BundleField]>,
+    },
+    AsyncReset,
+    SyncReset,
+    Reset,
+    Clock,
+    PhantomConst(ThePhantomConst),
+}
+
+impl<ArrayElement, PhantomConstInner> SerdeCanonicalType<ArrayElement, PhantomConstInner> {
+    pub(crate) fn as_serde_unexpected_str(&self) -> &'static str {
+        match self {
+            Self::UInt { .. } => "a UInt",
+            Self::SInt { .. } => "a SInt",
+            Self::Bool => "a Bool",
+            Self::Array { .. } => "an Array",
+            Self::Enum { .. } => "an Enum",
+            Self::Bundle { .. } => "a Bundle",
+            Self::AsyncReset => "an AsyncReset",
+            Self::SyncReset => "a SyncReset",
+            Self::Reset => "a Reset",
+            Self::Clock => "a Clock",
+            Self::PhantomConst(_) => "a PhantomConst",
+        }
+    }
+}
+
+impl<T: BaseType> From<T> for SerdeCanonicalType {
+    fn from(ty: T) -> Self {
+        let ty: CanonicalType = ty.into();
+        match ty {
+            CanonicalType::UInt(ty) => Self::UInt { width: ty.width() },
+            CanonicalType::SInt(ty) => Self::SInt { width: ty.width() },
+            CanonicalType::Bool(Bool {}) => Self::Bool,
+            CanonicalType::Array(ty) => Self::Array {
+                element: ty.element(),
+                len: ty.len(),
+            },
+            CanonicalType::Enum(ty) => Self::Enum {
+                variants: ty.variants(),
+            },
+            CanonicalType::Bundle(ty) => Self::Bundle {
+                fields: ty.fields(),
+            },
+            CanonicalType::AsyncReset(AsyncReset {}) => Self::AsyncReset,
+            CanonicalType::SyncReset(SyncReset {}) => Self::SyncReset,
+            CanonicalType::Reset(Reset {}) => Self::Reset,
+            CanonicalType::Clock(Clock {}) => Self::Clock,
+            CanonicalType::PhantomConst(ty) => Self::PhantomConst(SerdePhantomConst(ty.get())),
+        }
+    }
+}
+
+impl From<SerdeCanonicalType> for CanonicalType {
+    fn from(ty: SerdeCanonicalType) -> Self {
+        match ty {
+            SerdeCanonicalType::UInt { width } => Self::UInt(UInt::new(width)),
+            SerdeCanonicalType::SInt { width } => Self::SInt(SInt::new(width)),
+            SerdeCanonicalType::Bool => Self::Bool(Bool),
+            SerdeCanonicalType::Array { element, len } => Self::Array(Array::new(element, len)),
+            SerdeCanonicalType::Enum { variants } => Self::Enum(Enum::new(variants)),
+            SerdeCanonicalType::Bundle { fields } => Self::Bundle(Bundle::new(fields)),
+            SerdeCanonicalType::AsyncReset => Self::AsyncReset(AsyncReset),
+            SerdeCanonicalType::SyncReset => Self::SyncReset(SyncReset),
+            SerdeCanonicalType::Reset => Self::Reset(Reset),
+            SerdeCanonicalType::Clock => Self::Clock(Clock),
+            SerdeCanonicalType::PhantomConst(value) => {
+                Self::PhantomConst(PhantomConst::new(value.0))
+            }
+        }
+    }
+}
--- a/crates/fayalite/src/type_deduction.rs
+++ b/crates/fayalite/src/type_deduction.rs
@ -1,136 +0,0 @@
-use crate::{
-    expr::{Expr, ToExpr},
-    intern::Interned,
-    source_location::SourceLocation,
-    ty::{
-        impl_match_values_as_self, CanonicalType, CanonicalTypeKind, CanonicalValue, Connect, Type,
-        TypeEnum, Value, ValueEnum,
-    },
-};
-use bitvec::prelude::BitSlice;
-use std::{
-    fmt,
-    sync::atomic::{AtomicU64, Ordering},
-};
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-#[non_exhaustive]
-pub struct HitUndeducedType;
-
-impl HitUndeducedType {
-    /// if either input is [`Ok(false)`][Ok], return [`Ok(false)`][Ok],
-    /// otherwise if either input is [`Err(_)`][Err], return [`Err(_)`][Err],
-    /// otherwise return [`Ok(true)`][Ok].
-    pub fn reduce_and(l: Result<bool, Self>, r: Result<bool, Self>) -> Result<bool, Self> {
-        match (l, r) {
-            (Ok(false), _) | (_, Ok(false)) => Ok(false),
-            (Err(e), _) | (_, Err(e)) => Err(e),
-            (Ok(true), Ok(true)) => Ok(true),
-        }
-    }
-}
-
-impl fmt::Display for HitUndeducedType {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("encountered a not-yet-deduced type")
-    }
-}
-
-impl std::error::Error for HitUndeducedType {}
-
-#[derive(Copy, Debug, Clone, PartialEq, Eq, Hash)]
-pub struct UndeducedType {
-    id: u64,
-    mask_ty_id: u64,
-    source_location: SourceLocation,
-}
-
-impl UndeducedType {
-    #[track_caller]
-    pub fn new() -> Self {
-        Self::new_with_loc(SourceLocation::caller())
-    }
-    pub fn new_with_loc(source_location: SourceLocation) -> Self {
-        static NEXT_ID: AtomicU64 = AtomicU64::new(0);
-        let id = NEXT_ID.fetch_add(2, Ordering::Relaxed);
-        let mask_ty_id = id + 1;
-        Self {
-            id,
-            mask_ty_id,
-            source_location,
-        }
-    }
-    pub fn id(self) -> u64 {
-        self.id
-    }
-}
-
-impl<T> Connect<T> for UndeducedType {}
-
-impl Type for UndeducedType {
-    type CanonicalType = UndeducedType;
-    type Value = Deduce;
-    type CanonicalValue = Deduce;
-    type MaskType = UndeducedType;
-    type MaskValue = Deduce;
-    impl_match_values_as_self!();
-
-    fn mask_type(&self) -> Self::MaskType {
-        Self {
-            id: self.mask_ty_id,
-            mask_ty_id: self.mask_ty_id,
-            source_location: self.source_location,
-        }
-    }
-
-    fn canonical(&self) -> Self::CanonicalType {
-        *self
-    }
-
-    fn source_location(&self) -> SourceLocation {
-        self.source_location
-    }
-
-    fn type_enum(&self) -> TypeEnum {
-        TypeEnum::Deduce(*self)
-    }
-
-    fn from_canonical_type(t: Self::CanonicalType) -> Self {
-        t
-    }
-}
-
-impl CanonicalType for UndeducedType {
-    const CANONICAL_TYPE_KIND: CanonicalTypeKind = CanonicalTypeKind::Deduce;
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
-pub enum Deduce {}
-
-impl ToExpr for Deduce {
-    type Type = UndeducedType;
-
-    fn ty(&self) -> Self::Type {
-        match *self {}
-    }
-
-    fn to_expr(&self) -> Expr<<Self::Type as Type>::Value> {
-        match *self {}
-    }
-}
-
-impl Value for Deduce {
-    fn to_canonical(&self) -> <Self::Type as Type>::CanonicalValue {
-        *self
-    }
-}
-
-impl CanonicalValue for Deduce {
-    fn value_enum_impl(this: &Self) -> ValueEnum {
-        match *this {}
-    }
-
-    fn to_bits_impl(this: &Self) -> Result<Interned<BitSlice>, HitUndeducedType> {
-        match *this {}
-    }
-}
--- a/crates/fayalite/src/util.rs
+++ b/crates/fayalite/src/util.rs
@ -1,12 +1,28 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information

+pub(crate) mod alternating_cell;
 mod const_bool;
 mod const_cmp;
+mod const_usize;
 mod misc;
+mod scoped_ref;
+pub(crate) mod streaming_read_utf8;
+mod test_hasher;
+
+// allow easily switching the hasher crate-wide for testing
+#[cfg(feature = "unstable-test-hasher")]
+pub type DefaultBuildHasher = test_hasher::DefaultBuildHasher;
+#[cfg(not(feature = "unstable-test-hasher"))]
+pub(crate) type DefaultBuildHasher = hashbrown::DefaultHashBuilder;
+
+pub(crate) type HashMap<K, V> = hashbrown::HashMap<K, V, DefaultBuildHasher>;
+pub(crate) type HashSet<T> = hashbrown::HashSet<T, DefaultBuildHasher>;

 #[doc(inline)]
 pub use const_bool::{ConstBool, ConstBoolDispatch, ConstBoolDispatchTag, GenericConstBool};
+#[doc(inline)]
+pub use const_usize::{ConstUsize, GenericConstUsize};

 #[doc(inline)]
 pub use const_cmp::{
@ -14,7 +30,15 @@ pub use const_cmp::{
    const_usize_cmp,
 };

+#[doc(inline)]
+pub use scoped_ref::ScopedRef;
+
 #[doc(inline)]
 pub use misc::{
-    interned_bit, iter_eq_by, BitSliceWriteWithBase, DebugAsDisplay, DebugAsRawString, MakeMutSlice,
+    get_many_mut, interned_bit, iter_eq_by, BitSliceWriteWithBase, DebugAsDisplay,
+    DebugAsRawString, MakeMutSlice, RcWriter,
 };
+
+pub mod job_server;
+pub mod prefix_sum;
+pub mod ready_valid;
--- a/crates/fayalite/src/util/alternating_cell.rs
+++ b/crates/fayalite/src/util/alternating_cell.rs
@ -0,0 +1,122 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::util::DebugAsDisplay;
+use std::{
+    cell::{Cell, UnsafeCell},
+    fmt,
+};
+
+pub(crate) trait AlternatingCellMethods {
+    fn unique_to_shared(&mut self);
+    fn shared_to_unique(&mut self);
+}
+
+#[derive(Copy, Clone, Debug)]
+enum State {
+    Unique,
+    Shared,
+    Locked,
+}
+
+pub(crate) struct AlternatingCell<T: ?Sized> {
+    state: Cell<State>,
+    value: UnsafeCell<T>,
+}
+
+impl<T: ?Sized + fmt::Debug + AlternatingCellMethods> fmt::Debug for AlternatingCell<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("AlternatingCell")
+            .field(
+                self.try_share()
+                    .as_ref()
+                    .map(|v| -> &dyn fmt::Debug { v })
+                    .unwrap_or(&DebugAsDisplay("<...>")),
+            )
+            .finish()
+    }
+}
+
+impl<T: ?Sized> AlternatingCell<T> {
+    pub(crate) const fn new_shared(value: T) -> Self
+    where
+        T: Sized,
+    {
+        Self {
+            state: Cell::new(State::Shared),
+            value: UnsafeCell::new(value),
+        }
+    }
+    pub(crate) const fn new_unique(value: T) -> Self
+    where
+        T: Sized,
+    {
+        Self {
+            state: Cell::new(State::Unique),
+            value: UnsafeCell::new(value),
+        }
+    }
+    pub(crate) fn is_unique(&self) -> bool {
+        matches!(self.state.get(), State::Unique)
+    }
+    pub(crate) fn is_shared(&self) -> bool {
+        matches!(self.state.get(), State::Shared)
+    }
+    pub(crate) fn into_inner(self) -> T
+    where
+        T: Sized,
+    {
+        self.value.into_inner()
+    }
+    pub(crate) fn try_share(&self) -> Option<&T>
+    where
+        T: AlternatingCellMethods,
+    {
+        match self.state.get() {
+            State::Shared => {}
+            State::Unique => {
+                struct Locked<'a>(&'a Cell<State>);
+                impl Drop for Locked<'_> {
+                    fn drop(&mut self) {
+                        self.0.set(State::Shared);
+                    }
+                }
+                self.state.set(State::Locked);
+                let lock = Locked(&self.state);
+                // Safety: state is Locked, so nothing else will
+                // access value while calling unique_to_shared.
+                unsafe { &mut *self.value.get() }.unique_to_shared();
+                drop(lock);
+            }
+            State::Locked => return None,
+        }
+
+        // Safety: state is Shared so nothing will create any mutable
+        // references until the returned reference's lifetime expires.
+        Some(unsafe { &*self.value.get() })
+    }
+    #[track_caller]
+    pub(crate) fn share(&self) -> &T
+    where
+        T: AlternatingCellMethods,
+    {
+        let Some(retval) = self.try_share() else {
+            panic!("`share` called recursively");
+        };
+        retval
+    }
+    pub(crate) fn unique(&mut self) -> &mut T
+    where
+        T: AlternatingCellMethods,
+    {
+        match self.state.get() {
+            State::Shared => {
+                self.state.set(State::Unique);
+                self.value.get_mut().shared_to_unique();
+            }
+            State::Unique => {}
+            State::Locked => unreachable!(),
+        }
+        self.value.get_mut()
+    }
+}
--- a/crates/fayalite/src/util/const_bool.rs
+++ b/crates/fayalite/src/util/const_bool.rs
@ -1,5 +1,9 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
+use serde::{
+    de::{DeserializeOwned, Error, Unexpected},
+    Deserialize, Deserializer, Serialize, Serializer,
+};
 use std::{fmt::Debug, hash::Hash, mem::ManuallyDrop, ptr};

 mod sealed {
@ -9,7 +13,17 @@ mod sealed {
 /// # Safety
 /// the only implementation is `ConstBool<Self::VALUE>`
 pub unsafe trait GenericConstBool:
-    sealed::Sealed + Copy + Ord + Hash + Default + Debug + 'static + Send + Sync
+    sealed::Sealed
+    + Copy
+    + Ord
+    + Hash
+    + Default
+    + Debug
+    + 'static
+    + Send
+    + Sync
+    + Serialize
+    + DeserializeOwned
 {
    const VALUE: bool;
 }
@ -30,6 +44,32 @@ unsafe impl<const VALUE: bool> GenericConstBool for ConstBool<VALUE> {
    const VALUE: bool = VALUE;
 }

+impl<const VALUE: bool> Serialize for ConstBool<VALUE> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        VALUE.serialize(serializer)
+    }
+}
+
+impl<'de, const VALUE: bool> Deserialize<'de> for ConstBool<VALUE> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let value = bool::deserialize(deserializer)?;
+        if value == VALUE {
+            Ok(ConstBool)
+        } else {
+            Err(D::Error::invalid_value(
+                Unexpected::Bool(value),
+                &if VALUE { "true" } else { "false" },
+            ))
+        }
+    }
+}
+
 pub trait ConstBoolDispatchTag {
    type Type<Select: GenericConstBool>;
 }
--- a/crates/fayalite/src/util/const_usize.rs
+++ b/crates/fayalite/src/util/const_usize.rs
@ -0,0 +1,69 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use serde::{
+    de::{DeserializeOwned, Error, Unexpected},
+    Deserialize, Deserializer, Serialize, Serializer,
+};
+use std::{fmt::Debug, hash::Hash};
+
+mod sealed {
+    pub trait Sealed {}
+}
+
+/// the only implementation is `ConstUsize<Self::VALUE>`
+pub trait GenericConstUsize:
+    sealed::Sealed
+    + Copy
+    + Ord
+    + Hash
+    + Default
+    + Debug
+    + 'static
+    + Send
+    + Sync
+    + Serialize
+    + DeserializeOwned
+{
+    const VALUE: usize;
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct ConstUsize<const VALUE: usize>;
+
+impl<const VALUE: usize> Debug for ConstUsize<VALUE> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_tuple("ConstUsize").field(&Self::VALUE).finish()
+    }
+}
+
+impl<const VALUE: usize> sealed::Sealed for ConstUsize<VALUE> {}
+
+impl<const VALUE: usize> GenericConstUsize for ConstUsize<VALUE> {
+    const VALUE: usize = VALUE;
+}
+
+impl<const VALUE: usize> Serialize for ConstUsize<VALUE> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        VALUE.serialize(serializer)
+    }
+}
+
+impl<'de, const VALUE: usize> Deserialize<'de> for ConstUsize<VALUE> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let value = usize::deserialize(deserializer)?;
+        if value == VALUE {
+            Ok(ConstUsize)
+        } else {
+            Err(D::Error::invalid_value(
+                Unexpected::Unsigned(value as u64),
+                &&*VALUE.to_string(),
+            ))
+        }
+    }
+}
--- a/crates/fayalite/src/util/job_server.rs
+++ b/crates/fayalite/src/util/job_server.rs
@ -0,0 +1,193 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use ctor::ctor;
+use jobslot::{Acquired, Client};
+use std::{
+    ffi::OsString,
+    mem,
+    num::NonZeroUsize,
+    sync::{Condvar, Mutex, Once, OnceLock},
+    thread::spawn,
+};
+
+fn get_or_make_client() -> &'static Client {
+    #[ctor]
+    static CLIENT: OnceLock<Client> = unsafe {
+        match Client::from_env() {
+            Some(client) => OnceLock::from(client),
+            None => OnceLock::new(),
+        }
+    };
+
+    CLIENT.get_or_init(|| {
+        let mut available_parallelism = None;
+        let mut args = std::env::args_os().skip(1);
+        while let Some(arg) = args.next() {
+            const TEST_THREADS_OPTION: &'static [u8] = b"--test-threads";
+            if arg.as_encoded_bytes().starts_with(TEST_THREADS_OPTION) {
+                match arg.as_encoded_bytes().get(TEST_THREADS_OPTION.len()) {
+                    Some(b'=') => {
+                        let mut arg = arg.into_encoded_bytes();
+                        arg.drain(..=TEST_THREADS_OPTION.len());
+                        available_parallelism = Some(arg);
+                        break;
+                    }
+                    None => {
+                        available_parallelism = args.next().map(OsString::into_encoded_bytes);
+                        break;
+                    }
+                    _ => {}
+                }
+            }
+        }
+        let available_parallelism = if let Some(available_parallelism) = available_parallelism
+            .as_deref()
+            .and_then(|v| std::str::from_utf8(v).ok())
+            .and_then(|v| v.parse().ok())
+        {
+            available_parallelism
+        } else if let Ok(available_parallelism) = std::thread::available_parallelism() {
+            available_parallelism
+        } else {
+            NonZeroUsize::new(1).unwrap()
+        };
+        Client::new_with_fifo(available_parallelism.get() - 1).expect("failed to create job server")
+    })
+}
+
+struct State {
+    waiting_count: usize,
+    available: Vec<Acquired>,
+    implicit_available: bool,
+}
+
+impl State {
+    fn total_available(&self) -> usize {
+        self.available.len() + self.implicit_available as usize
+    }
+    fn additional_waiting(&self) -> usize {
+        self.waiting_count.saturating_sub(self.total_available())
+    }
+}
+
+static STATE: Mutex<State> = Mutex::new(State {
+    waiting_count: 0,
+    available: Vec::new(),
+    implicit_available: true,
+});
+static COND_VAR: Condvar = Condvar::new();
+
+#[derive(Debug)]
+enum AcquiredJobInner {
+    FromJobServer(Acquired),
+    ImplicitJob,
+}
+
+#[derive(Debug)]
+pub struct AcquiredJob {
+    job: AcquiredJobInner,
+}
+
+impl AcquiredJob {
+    fn start_acquire_thread() {
+        static STARTED_THREAD: Once = Once::new();
+        STARTED_THREAD.call_once(|| {
+            spawn(|| {
+                let mut acquired = None;
+                let client = get_or_make_client();
+                let mut state = STATE.lock().unwrap();
+                loop {
+                    state = if state.additional_waiting() == 0 {
+                        if acquired.is_some() {
+                            drop(state);
+                            drop(acquired.take()); // drop Acquired outside of lock
+                            STATE.lock().unwrap()
+                        } else {
+                            COND_VAR.wait(state).unwrap()
+                        }
+                    } else if acquired.is_some() {
+                        // allocate space before moving Acquired to ensure we
+                        // drop Acquired outside of the lock on panic
+                        state.available.reserve(1);
+                        state.available.push(acquired.take().unwrap());
+                        COND_VAR.notify_all();
+                        state
+                    } else {
+                        drop(state);
+                        acquired = Some(
+                            client
+                                .acquire()
+                                .expect("can't acquire token from job server"),
+                        );
+                        STATE.lock().unwrap()
+                    };
+                }
+            });
+        });
+    }
+    fn acquire_inner(block: bool) -> Option<Self> {
+        Self::start_acquire_thread();
+        let mut state = STATE.lock().unwrap();
+        loop {
+            if let Some(acquired) = state.available.pop() {
+                return Some(Self {
+                    job: AcquiredJobInner::FromJobServer(acquired),
+                });
+            }
+            if state.implicit_available {
+                state.implicit_available = false;
+                return Some(Self {
+                    job: AcquiredJobInner::ImplicitJob,
+                });
+            }
+            if !block {
+                return None;
+            }
+            state.waiting_count += 1;
+            state = COND_VAR.wait(state).unwrap();
+            state.waiting_count -= 1;
+        }
+    }
+    pub fn try_acquire() -> Option<Self> {
+        Self::acquire_inner(false)
+    }
+    pub fn acquire() -> Self {
+        Self::acquire_inner(true).expect("failed to acquire token")
+    }
+    pub fn run_command<R>(
+        &mut self,
+        cmd: std::process::Command,
+        f: impl FnOnce(&mut std::process::Command) -> std::io::Result<R>,
+    ) -> std::io::Result<R> {
+        get_or_make_client().configure_make_and_run_with_fifo(cmd, f)
+    }
+}
+
+impl Drop for AcquiredJob {
+    fn drop(&mut self) {
+        let mut state = STATE.lock().unwrap();
+        match &self.job {
+            AcquiredJobInner::FromJobServer(_) => {
+                if state.waiting_count > state.available.len() + state.implicit_available as usize {
+                    // allocate space before moving Acquired to ensure we
+                    // drop Acquired outside of the lock on panic
+                    state.available.reserve(1);
+                    let AcquiredJobInner::FromJobServer(acquired) =
+                        mem::replace(&mut self.job, AcquiredJobInner::ImplicitJob)
+                    else {
+                        unreachable!()
+                    };
+                    state.available.push(acquired);
+                    COND_VAR.notify_all();
+                }
+            }
+            AcquiredJobInner::ImplicitJob => {
+                state.implicit_available = true;
+                if state.waiting_count > state.available.len() {
+                    COND_VAR.notify_all();
+                }
+            }
+        }
+    }
+}
--- a/crates/fayalite/src/util/misc.rs
+++ b/crates/fayalite/src/util/misc.rs
@ -3,6 +3,7 @@
 use crate::intern::{Intern, Interned};
 use bitvec::{bits, order::Lsb0, slice::BitSlice, view::BitView};
 use std::{
+    cell::Cell,
    fmt::{self, Debug, Write},
    rc::Rc,
    sync::{Arc, OnceLock},
@ -94,9 +95,15 @@ pub fn interned_bit(v: bool) -> Interned<BitSlice> {
    RETVAL.get_or_init(|| [bits![0; 1].intern(), bits![1; 1].intern()])[v as usize]
 }

-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone)]
 pub struct BitSliceWriteWithBase<'a>(pub &'a BitSlice);

+impl<'a> Debug for BitSliceWriteWithBase<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{self:#x}")
+    }
+}
+
 impl BitSliceWriteWithBase<'_> {
    fn fmt_with_base<const BITS_PER_DIGIT: usize, const UPPER_CASE: bool>(
        self,
@ -155,3 +162,66 @@ impl fmt::UpperHex for BitSliceWriteWithBase<'_> {
        self.fmt_with_base::<4, true>(f)
    }
 }
+
+#[inline]
+#[track_caller]
+pub fn get_many_mut<T, const N: usize>(slice: &mut [T], indexes: [usize; N]) -> [&mut T; N] {
+    for i in 0..N {
+        for j in 0..i {
+            assert!(indexes[i] != indexes[j], "duplicate index");
+        }
+        assert!(indexes[i] < slice.len(), "index out of bounds");
+    }
+    // Safety: checked that no indexes are duplicates and no indexes are out of bounds
+    unsafe {
+        let base = slice.as_mut_ptr(); // convert to a raw pointer before loop to avoid aliasing with &mut [T]
+        std::array::from_fn(|i| &mut *base.add(indexes[i]))
+    }
+}
+
+#[derive(Clone, Default)]
+pub struct RcWriter(Rc<Cell<Vec<u8>>>);
+
+impl Debug for RcWriter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.borrow_impl(|buf| {
+            f.debug_tuple("RcWriter")
+                .field(&DebugAsDisplay(format_args!("b\"{}\"", buf.escape_ascii())))
+                .finish()
+        })
+    }
+}
+
+impl RcWriter {
+    fn borrow_impl<R>(&self, f: impl FnOnce(&mut Vec<u8>) -> R) -> R {
+        let buf = Cell::take(&self.0);
+        struct PutBackOnDrop<'a> {
+            buf: Vec<u8>,
+            this: &'a RcWriter,
+        }
+        impl Drop for PutBackOnDrop<'_> {
+            fn drop(&mut self) {
+                self.this.0.set(std::mem::take(&mut self.buf));
+            }
+        }
+        let mut buf = PutBackOnDrop { buf, this: self };
+        f(&mut buf.buf)
+    }
+    pub fn borrow<R>(&mut self, f: impl FnOnce(&mut Vec<u8>) -> R) -> R {
+        self.borrow_impl(f)
+    }
+    pub fn take(&mut self) -> Vec<u8> {
+        Cell::take(&self.0)
+    }
+}
+
+impl std::io::Write for RcWriter {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.borrow(|v| v.extend_from_slice(buf));
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        Ok(())
+    }
+}
--- a/crates/fayalite/src/util/prefix_sum.rs
+++ b/crates/fayalite/src/util/prefix_sum.rs
@ -0,0 +1,839 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+// code derived from:
+// https://web.archive.org/web/20250303054010/https://git.libre-soc.org/?p=nmutil.git;a=blob;f=src/nmutil/prefix_sum.py;hb=effeb28e5848392adddcdad1f6e7a098f2a44c9c
+
+use crate::intern::{Intern, Interned, Memoize};
+use std::{borrow::Cow, num::NonZeroUsize};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct PrefixSumOp {
+    pub lhs_index: usize,
+    pub rhs_and_dest_index: NonZeroUsize,
+    pub row: u32,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub struct DiagramConfig {
+    pub space: Cow<'static, str>,
+    pub vertical_bar: Cow<'static, str>,
+    pub plus: Cow<'static, str>,
+    pub slant: Cow<'static, str>,
+    pub connect: Cow<'static, str>,
+    pub no_connect: Cow<'static, str>,
+    pub padding: usize,
+}
+
+impl DiagramConfig {
+    pub const fn new() -> Self {
+        Self {
+            space: Cow::Borrowed(" "),
+            vertical_bar: Cow::Borrowed("|"),
+            plus: Cow::Borrowed("\u{2295}"), // ⊕
+            slant: Cow::Borrowed(r"\"),
+            connect: Cow::Borrowed("\u{25CF}"), // ●
+            no_connect: Cow::Borrowed("X"),
+            padding: 1,
+        }
+    }
+    pub fn draw(self, ops: impl IntoIterator<Item = PrefixSumOp>, item_count: usize) -> String {
+        #[derive(Copy, Clone, Debug)]
+        struct DiagramCell {
+            slant: bool,
+            plus: bool,
+            tee: bool,
+        }
+        let mut ops_by_row: Vec<Vec<PrefixSumOp>> = Vec::new();
+        let mut last_row = 0;
+        ops.into_iter().for_each(|op| {
+            assert!(
+                op.lhs_index < op.rhs_and_dest_index.get(),
+                "invalid PrefixSumOp! lhs_index must be less \
+                than rhs_and_dest_index: {op:?}",
+            );
+            assert!(
+                op.row >= last_row,
+                "invalid PrefixSumOp! row must \
+                not decrease (row last was: {last_row}): {op:?}",
+            );
+            let ops = if op.row > last_row || ops_by_row.is_empty() {
+                ops_by_row.push(vec![]);
+                ops_by_row.last_mut().expect("just pushed")
+            } else {
+                ops_by_row
+                    .last_mut()
+                    .expect("just checked if ops_by_row is empty")
+            };
+            if let Some(last) = ops.last() {
+                assert!(
+                    op.rhs_and_dest_index < last.rhs_and_dest_index,
+                    "invalid PrefixSumOp! rhs_and_dest_index must strictly \
+                    decrease in a row:\nthis op: {op:?}\nlast op: {last:?}",
+                );
+            }
+            ops.push(op);
+            last_row = op.row;
+        });
+        let blank_row = || {
+            vec![
+                DiagramCell {
+                    slant: false,
+                    plus: false,
+                    tee: false
+                };
+                item_count
+            ]
+        };
+        let mut cells = vec![blank_row()];
+        for ops in ops_by_row {
+            let max_distance = ops
+                .iter()
+                .map(
+                    |&PrefixSumOp {
+                         lhs_index,
+                         rhs_and_dest_index,
+                         ..
+                     }| { rhs_and_dest_index.get() - lhs_index },
+                )
+                .max()
+                .expect("ops is known to be non-empty");
+            cells.extend((0..max_distance).map(|_| blank_row()));
+            for op in ops {
+                let mut y = cells.len() - 1;
+                assert!(
+                    op.rhs_and_dest_index.get() < item_count,
+                    "invalid PrefixSumOp! rhs_and_dest_index must be \
+                    less than item_count ({item_count}): {op:?}",
+                );
+                let mut x = op.rhs_and_dest_index.get();
+                cells[y][x].plus = true;
+                x -= 1;
+                y -= 1;
+                while op.lhs_index < x {
+                    cells[y][x].slant = true;
+                    x -= 1;
+                    y -= 1;
+                }
+                cells[y][x].tee = true;
+            }
+        }
+        let mut retval = String::new();
+        let mut row_text = vec![String::new(); 2 * self.padding + 1];
+        for cells_row in cells {
+            for cell in cells_row {
+                // top padding
+                for y in 0..self.padding {
+                    // top left padding
+                    for x in 0..self.padding {
+                        row_text[y] += if x == y && (cell.plus || cell.slant) {
+                            &self.slant
+                        } else {
+                            &self.space
+                        };
+                    }
+                    // top vertical bar
+                    row_text[y] += &self.vertical_bar;
+                    // top right padding
+                    for _ in 0..self.padding {
+                        row_text[y] += &self.space;
+                    }
+                }
+                // center left padding
+                for _ in 0..self.padding {
+                    row_text[self.padding] += &self.space;
+                }
+                // center
+                row_text[self.padding] += if cell.plus {
+                    &self.plus
+                } else if cell.tee {
+                    &self.connect
+                } else if cell.slant {
+                    &self.no_connect
+                } else {
+                    &self.vertical_bar
+                };
+                // center right padding
+                for _ in 0..self.padding {
+                    row_text[self.padding] += &self.space;
+                }
+                let bottom_padding_start = self.padding + 1;
+                let bottom_padding_last = self.padding * 2;
+                // bottom padding
+                for y in bottom_padding_start..=bottom_padding_last {
+                    // bottom left padding
+                    for _ in 0..self.padding {
+                        row_text[y] += &self.space;
+                    }
+                    // bottom vertical bar
+                    row_text[y] += &self.vertical_bar;
+                    // bottom right padding
+                    for x in bottom_padding_start..=bottom_padding_last {
+                        row_text[y] += if x == y && (cell.tee || cell.slant) {
+                            &self.slant
+                        } else {
+                            &self.space
+                        };
+                    }
+                }
+            }
+            for line in &mut row_text {
+                retval += line.trim_end();
+                retval += "\n";
+                line.clear();
+            }
+        }
+        retval
+    }
+}
+
+impl Default for DiagramConfig {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl PrefixSumOp {
+    pub fn diagram(ops: impl IntoIterator<Item = Self>, item_count: usize) -> String {
+        Self::diagram_with_config(ops, item_count, DiagramConfig::new())
+    }
+    pub fn diagram_with_config(
+        ops: impl IntoIterator<Item = Self>,
+        item_count: usize,
+        config: DiagramConfig,
+    ) -> String {
+        config.draw(ops, item_count)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub enum PrefixSumAlgorithm {
+    /// Uses the algorithm from:
+    /// <https://en.wikipedia.org/wiki/Prefix_sum#Algorithm_1:_Shorter_span,_more_parallel>
+    LowLatency,
+    /// Uses the algorithm from:
+    /// <https://en.wikipedia.org/wiki/Prefix_sum#Algorithm_2:_Work-efficient>
+    WorkEfficient,
+}
+
+impl PrefixSumAlgorithm {
+    fn ops_impl(self, item_count: usize) -> Vec<PrefixSumOp> {
+        let mut retval = Vec::new();
+        let mut distance = 1;
+        let mut row = 0;
+        while distance < item_count {
+            let double_distance = distance
+                .checked_mul(2)
+                .expect("prefix-sum item_count is too big");
+            let (start, step) = match self {
+                Self::LowLatency => (distance, 1),
+                Self::WorkEfficient => (double_distance - 1, double_distance),
+            };
+            for rhs_and_dest_index in (start..item_count).step_by(step).rev() {
+                let Some(rhs_and_dest_index) = NonZeroUsize::new(rhs_and_dest_index) else {
+                    unreachable!();
+                };
+                let lhs_index = rhs_and_dest_index.get() - distance;
+                retval.push(PrefixSumOp {
+                    lhs_index,
+                    rhs_and_dest_index,
+                    row,
+                });
+            }
+            distance = double_distance;
+            row += 1;
+        }
+        match self {
+            Self::LowLatency => {}
+            Self::WorkEfficient => {
+                distance /= 2;
+                while distance >= 1 {
+                    let start = distance
+                        .checked_mul(3)
+                        .expect("prefix-sum item_count is too big")
+                        - 1;
+                    for rhs_and_dest_index in (start..item_count).step_by(distance * 2).rev() {
+                        let Some(rhs_and_dest_index) = NonZeroUsize::new(rhs_and_dest_index) else {
+                            unreachable!();
+                        };
+                        let lhs_index = rhs_and_dest_index.get() - distance;
+                        retval.push(PrefixSumOp {
+                            lhs_index,
+                            rhs_and_dest_index,
+                            row,
+                        });
+                    }
+                    row += 1;
+                    distance /= 2;
+                }
+            }
+        }
+        retval
+    }
+    pub fn ops(self, item_count: usize) -> Interned<[PrefixSumOp]> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct MyMemoize(PrefixSumAlgorithm);
+        impl Memoize for MyMemoize {
+            type Input = usize;
+            type InputOwned = usize;
+            type Output = Interned<[PrefixSumOp]>;
+
+            fn inner(self, item_count: &Self::Input) -> Self::Output {
+                Intern::intern_owned(self.0.ops_impl(*item_count))
+            }
+        }
+        MyMemoize(self).get_owned(item_count)
+    }
+    pub fn run<T>(self, items: impl IntoIterator<Item = T>, f: impl FnMut(&T, &T) -> T) -> Vec<T> {
+        let mut items = Vec::from_iter(items);
+        self.run_on_slice(&mut items, f);
+        items
+    }
+    pub fn run_on_slice<T>(self, items: &mut [T], mut f: impl FnMut(&T, &T) -> T) -> &mut [T] {
+        self.ops(items.len()).into_iter().for_each(
+            |PrefixSumOp {
+                 lhs_index,
+                 rhs_and_dest_index,
+                 row: _,
+             }| {
+                items[rhs_and_dest_index.get()] =
+                    f(&items[lhs_index], &items[rhs_and_dest_index.get()]);
+            },
+        );
+        items
+    }
+    pub fn filtered_ops(
+        self,
+        item_live_out_flags: impl IntoIterator<Item = bool>,
+    ) -> Vec<PrefixSumOp> {
+        let mut item_live_out_flags = Vec::from_iter(item_live_out_flags);
+        let prefix_sum_ops = self.ops(item_live_out_flags.len());
+        let mut ops_live_flags = vec![false; prefix_sum_ops.len()];
+        for (
+            op_index,
+            &PrefixSumOp {
+                lhs_index,
+                rhs_and_dest_index,
+                row: _,
+            },
+        ) in prefix_sum_ops.iter().enumerate().rev()
+        {
+            let live = item_live_out_flags[rhs_and_dest_index.get()];
+            item_live_out_flags[lhs_index] |= live;
+            ops_live_flags[op_index] = live;
+        }
+        prefix_sum_ops
+            .into_iter()
+            .zip(ops_live_flags)
+            .filter_map(|(op, live)| live.then_some(op))
+            .collect()
+    }
+    pub fn reduce_ops(self, item_count: usize) -> Interned<[PrefixSumOp]> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+        struct MyMemoize(PrefixSumAlgorithm);
+        impl Memoize for MyMemoize {
+            type Input = usize;
+            type InputOwned = usize;
+            type Output = Interned<[PrefixSumOp]>;
+
+            fn inner(self, item_count: &Self::Input) -> Self::Output {
+                let mut item_live_out_flags = vec![false; *item_count];
+                let Some(last_item_live_out_flag) = item_live_out_flags.last_mut() else {
+                    return Interned::default();
+                };
+                *last_item_live_out_flag = true;
+                Intern::intern_owned(self.0.filtered_ops(item_live_out_flags))
+            }
+        }
+        MyMemoize(self).get_owned(item_count)
+    }
+}
+
+pub fn reduce_ops(item_count: usize) -> Interned<[PrefixSumOp]> {
+    PrefixSumAlgorithm::LowLatency.reduce_ops(item_count)
+}
+
+pub fn reduce<T>(items: impl IntoIterator<Item = T>, mut f: impl FnMut(T, T) -> T) -> Option<T> {
+    let mut items: Vec<_> = items.into_iter().map(Some).collect();
+    for op in reduce_ops(items.len()) {
+        let (Some(lhs), Some(rhs)) = (
+            items[op.lhs_index].take(),
+            items[op.rhs_and_dest_index.get()].take(),
+        ) else {
+            unreachable!();
+        };
+        items[op.rhs_and_dest_index.get()] = Some(f(lhs, rhs));
+    }
+    items.last_mut().and_then(Option::take)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn input_strings() -> [String; 9] {
+        std::array::from_fn(|i| String::from_utf8(vec![b'a' + i as u8]).unwrap())
+    }
+
+    #[test]
+    fn test_prefix_sum_strings() {
+        let input = input_strings();
+        let expected: Vec<String> = input
+            .iter()
+            .scan(String::new(), |l, r| {
+                *l += r;
+                Some(l.clone())
+            })
+            .collect();
+        println!("expected: {expected:?}");
+        assert_eq!(
+            *PrefixSumAlgorithm::WorkEfficient
+                .run_on_slice(&mut input.clone(), |l, r| l.to_string() + r),
+            *expected
+        );
+        assert_eq!(
+            *PrefixSumAlgorithm::LowLatency
+                .run_on_slice(&mut input.clone(), |l, r| l.to_string() + r),
+            *expected
+        );
+    }
+
+    #[test]
+    fn test_reduce_string() {
+        let input = input_strings();
+        let expected = input.clone().into_iter().reduce(|l, r| l + &r);
+        assert_eq!(reduce(input, |l, r| l + &r), expected);
+    }
+
+    fn op(lhs_index: usize, rhs_and_dest_index: usize, row: u32) -> PrefixSumOp {
+        PrefixSumOp {
+            lhs_index,
+            rhs_and_dest_index: NonZeroUsize::new(rhs_and_dest_index).expect("should be non-zero"),
+            row,
+        }
+    }
+
+    #[test]
+    fn test_reduce_ops_9() {
+        let expected = vec![
+            op(7, 8, 0),
+            op(5, 6, 0),
+            op(3, 4, 0),
+            op(1, 2, 0),
+            op(6, 8, 1),
+            op(2, 4, 1),
+            op(4, 8, 2),
+            op(0, 8, 3),
+        ];
+        println!("expected: {expected:#?}");
+        let ops = reduce_ops(9);
+        println!("ops: {ops:#?}");
+        assert_eq!(*ops, *expected);
+    }
+
+    #[test]
+    fn test_reduce_ops_8() {
+        let expected = vec![
+            op(6, 7, 0),
+            op(4, 5, 0),
+            op(2, 3, 0),
+            op(0, 1, 0),
+            op(5, 7, 1),
+            op(1, 3, 1),
+            op(3, 7, 2),
+        ];
+        println!("expected: {expected:#?}");
+        let ops = reduce_ops(8);
+        println!("ops: {ops:#?}");
+        assert_eq!(*ops, *expected);
+    }
+
+    #[test]
+    fn test_count_ones() {
+        for width in 0..=10u32 {
+            for v in 0..1u32 << width {
+                let expected = v.count_ones();
+                assert_eq!(
+                    reduce((0..width).map(|i| (v >> i) & 1), |l, r| l + r).unwrap_or(0),
+                    expected,
+                    "v={v:#X}"
+                );
+            }
+        }
+    }
+
+    #[track_caller]
+    fn test_diagram(ops: impl IntoIterator<Item = PrefixSumOp>, item_count: usize, expected: &str) {
+        let text = PrefixSumOp::diagram_with_config(
+            ops,
+            item_count,
+            DiagramConfig {
+                plus: Cow::Borrowed("@"),
+                ..Default::default()
+            },
+        );
+        println!("text:\n{text}\n");
+        assert_eq!(text, expected);
+    }
+
+    #[test]
+    fn test_work_efficient_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            PrefixSumAlgorithm::WorkEfficient.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |
+ |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |
+ | \|  | \|  | \|  | \|  | \|  | \|  | \|  | \|
+ |  @  |  @  |  @  |  @  |  @  |  @  |  @  |  @
+ |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |
+ |  | \|  |  |  | \|  |  |  | \|  |  |  | \|  |
+ |  |  X  |  |  |  X  |  |  |  X  |  |  |  X  |
+ |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |
+ |  |  | \|  |  |  | \|  |  |  | \|  |  |  | \|
+ |  |  |  @  |  |  |  @  |  |  |  @  |  |  |  @
+ |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  X  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  | \|  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  X  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  | \|  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  @  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  X  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  ●  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  ●  |  |  |  ●  |  |  |  @  |  |  |  |
+ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  | \|  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  X  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  | \|  |  |  | \|  |  |
+ |  ●  |  ●  |  @  |  ●  |  @  |  ●  |  @  |  |
+ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |
+ |  | \|  | \|  | \|  | \|  | \|  | \|  | \|  |
+ |  |  @  |  @  |  @  |  @  |  @  |  @  |  @  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_low_latency_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            PrefixSumAlgorithm::LowLatency.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  ●  |
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ | \| \| \| \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  @  @  @  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ | \| \| \| \| \| \| \| \| \| \| \| \| \| \|  |
+ |  X  X  X  X  X  X  X  X  X  X  X  X  X  X  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  | \| \| \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  ●  @  @  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |
+ | \| \| \| \| \| \| \| \| \| \| \| \|  |  |  |
+ |  X  X  X  X  X  X  X  X  X  X  X  X  |  |  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |
+ |  | \| \| \| \| \| \| \| \| \| \| \| \|  |  |
+ |  |  X  X  X  X  X  X  X  X  X  X  X  X  |  |
+ |  |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ |  |  | \| \| \| \| \| \| \| \| \| \| \| \|  |
+ |  |  |  X  X  X  X  X  X  X  X  X  X  X  X  |
+ |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  |  |  | \| \| \| \| \| \| \| \| \| \| \| \|
+ ●  ●  ●  ●  @  @  @  @  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |  |  |
+ | \| \| \| \| \| \| \| \|  |  |  |  |  |  |  |
+ |  X  X  X  X  X  X  X  X  |  |  |  |  |  |  |
+ |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |  |
+ |  | \| \| \| \| \| \| \| \|  |  |  |  |  |  |
+ |  |  X  X  X  X  X  X  X  X  |  |  |  |  |  |
+ |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |  |
+ |  |  | \| \| \| \| \| \| \| \|  |  |  |  |  |
+ |  |  |  X  X  X  X  X  X  X  X  |  |  |  |  |
+ |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |  |
+ |  |  |  | \| \| \| \| \| \| \| \|  |  |  |  |
+ |  |  |  |  X  X  X  X  X  X  X  X  |  |  |  |
+ |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |  |
+ |  |  |  |  | \| \| \| \| \| \| \| \|  |  |  |
+ |  |  |  |  |  X  X  X  X  X  X  X  X  |  |  |
+ |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |  |
+ |  |  |  |  |  | \| \| \| \| \| \| \| \|  |  |
+ |  |  |  |  |  |  X  X  X  X  X  X  X  X  |  |
+ |  |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |  |
+ |  |  |  |  |  |  | \| \| \| \| \| \| \| \|  |
+ |  |  |  |  |  |  |  X  X  X  X  X  X  X  X  |
+ |  |  |  |  |  |  |  |\ |\ |\ |\ |\ |\ |\ |\ |
+ |  |  |  |  |  |  |  | \| \| \| \| \| \| \| \|
+ |  |  |  |  |  |  |  |  @  @  @  @  @  @  @  @
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_work_efficient_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            PrefixSumAlgorithm::WorkEfficient.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  |
+ |\ |  |\ |  |\ |  |\ |  |
+ | \|  | \|  | \|  | \|  |
+ |  @  |  @  |  @  |  @  |
+ |  |\ |  |  |  |\ |  |  |
+ |  | \|  |  |  | \|  |  |
+ |  |  X  |  |  |  X  |  |
+ |  |  |\ |  |  |  |\ |  |
+ |  |  | \|  |  |  | \|  |
+ |  |  |  @  |  |  |  @  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  ●  |  |  |  @  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  ●  |  ●  |  @  |  ●  |
+ |  |\ |  |\ |  |\ |  |\ |
+ |  | \|  | \|  | \|  | \|
+ |  |  @  |  @  |  @  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_low_latency_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            PrefixSumAlgorithm::LowLatency.ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ ●  ●  ●  ●  ●  ●  ●  ●  |
+ |\ |\ |\ |\ |\ |\ |\ |\ |
+ | \| \| \| \| \| \| \| \|
+ ●  @  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |\ |\ |  |
+ | \| \| \| \| \| \| \|  |
+ |  X  X  X  X  X  X  X  |
+ |  |\ |\ |\ |\ |\ |\ |\ |
+ |  | \| \| \| \| \| \| \|
+ ●  ●  @  @  @  @  @  @  @
+ |\ |\ |\ |\ |\ |  |  |  |
+ | \| \| \| \| \|  |  |  |
+ |  X  X  X  X  X  |  |  |
+ |  |\ |\ |\ |\ |\ |  |  |
+ |  | \| \| \| \| \|  |  |
+ |  |  X  X  X  X  X  |  |
+ |  |  |\ |\ |\ |\ |\ |  |
+ |  |  | \| \| \| \| \|  |
+ |  |  |  X  X  X  X  X  |
+ |  |  |  |\ |\ |\ |\ |\ |
+ |  |  |  | \| \| \| \| \|
+ ●  |  |  |  @  @  @  @  @
+ |\ |  |  |  |  |  |  |  |
+ | \|  |  |  |  |  |  |  |
+ |  X  |  |  |  |  |  |  |
+ |  |\ |  |  |  |  |  |  |
+ |  | \|  |  |  |  |  |  |
+ |  |  X  |  |  |  |  |  |
+ |  |  |\ |  |  |  |  |  |
+ |  |  | \|  |  |  |  |  |
+ |  |  |  X  |  |  |  |  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_reduce_diagram_16() {
+        let item_count = 16;
+        test_diagram(
+            reduce_ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+ ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |  ●  |
+ |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |  |\ |
+ | \|  | \|  | \|  | \|  | \|  | \|  | \|  | \|
+ |  @  |  @  |  @  |  @  |  @  |  @  |  @  |  @
+ |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |  |
+ |  | \|  |  |  | \|  |  |  | \|  |  |  | \|  |
+ |  |  X  |  |  |  X  |  |  |  X  |  |  |  X  |
+ |  |  |\ |  |  |  |\ |  |  |  |\ |  |  |  |\ |
+ |  |  | \|  |  |  | \|  |  |  | \|  |  |  | \|
+ |  |  |  @  |  |  |  @  |  |  |  @  |  |  |  @
+ |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  | \|  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  X  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  | \|  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  X  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  | \|  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  X  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  | \|  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  @  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  | \|  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  X  |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  | \|  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  X  |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  | \|  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  X  |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  | \|  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  X  |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+
+    #[test]
+    fn test_reduce_diagram_9() {
+        let item_count = 9;
+        test_diagram(
+            reduce_ops(item_count),
+            item_count,
+            &r"
+ |  |  |  |  |  |  |  |  |
+ |  ●  |  ●  |  ●  |  ●  |
+ |  |\ |  |\ |  |\ |  |\ |
+ |  | \|  | \|  | \|  | \|
+ |  |  @  |  @  |  @  |  @
+ |  |  |\ |  |  |  |\ |  |
+ |  |  | \|  |  |  | \|  |
+ |  |  |  X  |  |  |  X  |
+ |  |  |  |\ |  |  |  |\ |
+ |  |  |  | \|  |  |  | \|
+ |  |  |  |  @  |  |  |  @
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ ●  |  |  |  |  |  |  |  @
+ |\ |  |  |  |  |  |  |  |
+ | \|  |  |  |  |  |  |  |
+ |  X  |  |  |  |  |  |  |
+ |  |\ |  |  |  |  |  |  |
+ |  | \|  |  |  |  |  |  |
+ |  |  X  |  |  |  |  |  |
+ |  |  |\ |  |  |  |  |  |
+ |  |  | \|  |  |  |  |  |
+ |  |  |  X  |  |  |  |  |
+ |  |  |  |\ |  |  |  |  |
+ |  |  |  | \|  |  |  |  |
+ |  |  |  |  X  |  |  |  |
+ |  |  |  |  |\ |  |  |  |
+ |  |  |  |  | \|  |  |  |
+ |  |  |  |  |  X  |  |  |
+ |  |  |  |  |  |\ |  |  |
+ |  |  |  |  |  | \|  |  |
+ |  |  |  |  |  |  X  |  |
+ |  |  |  |  |  |  |\ |  |
+ |  |  |  |  |  |  | \|  |
+ |  |  |  |  |  |  |  X  |
+ |  |  |  |  |  |  |  |\ |
+ |  |  |  |  |  |  |  | \|
+ |  |  |  |  |  |  |  |  @
+ |  |  |  |  |  |  |  |  |
+"[1..], // trim newline at start
+        );
+    }
+}
--- a/crates/fayalite/src/util/ready_valid.rs
+++ b/crates/fayalite/src/util/ready_valid.rs
@ -0,0 +1,566 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use crate::{memory::splat_mask, prelude::*};
+use std::num::NonZeroUsize;
+
+#[hdl]
+pub struct ReadyValid<T> {
+    pub data: HdlOption<T>,
+    #[hdl(flip)]
+    pub ready: Bool,
+}
+
+impl<T: Type> ReadyValid<T> {
+    #[hdl]
+    pub fn firing(expr: Expr<Self>) -> Expr<Bool> {
+        #[hdl]
+        let firing: Bool = wire();
+        #[hdl]
+        match expr.data {
+            HdlNone => connect(firing, false),
+            HdlSome(_) => connect(firing, expr.ready),
+        }
+        firing
+    }
+    #[hdl]
+    pub fn firing_data(expr: impl ToExpr<Type = Self>) -> Expr<HdlOption<T>> {
+        let expr = expr.to_expr();
+        let option_ty = Expr::ty(expr).data;
+        #[hdl]
+        let firing_data = wire(option_ty);
+        connect(firing_data, option_ty.HdlNone());
+        #[hdl]
+        if expr.ready {
+            connect(firing_data, expr.data);
+        }
+        firing_data
+    }
+    #[hdl]
+    pub fn map<R: Type>(
+        expr: Expr<Self>,
+        f: impl FnOnce(Expr<T>) -> Expr<R>,
+    ) -> Expr<ReadyValid<R>> {
+        let data = HdlOption::map(expr.data, f);
+        #[hdl]
+        let mapped = wire(ReadyValid[Expr::ty(data).HdlSome]);
+        connect(mapped.data, data);
+        connect(expr.ready, mapped.ready);
+        mapped
+    }
+}
+
+/// This debug port is only meant to assist the formal proof of the queue.
+#[cfg(test)]
+#[doc(hidden)]
+#[hdl]
+pub struct QueueDebugPort<Element, Index> {
+    #[hdl(flip)]
+    index_to_check: Index,
+    stored: Element,
+    inp_index: Index,
+    out_index: Index,
+}
+
+#[hdl_module]
+pub fn queue<T: Type>(
+    ty: T,
+    capacity: NonZeroUsize,
+    inp_ready_is_comb: bool,
+    out_valid_is_comb: bool,
+) {
+    let count_ty = UInt::range_inclusive(0..=capacity.get());
+    let index_ty = UInt::range(0..capacity.get());
+
+    #[hdl]
+    let cd: ClockDomain = m.input();
+    #[hdl]
+    let inp: ReadyValid<T> = m.input(ReadyValid[ty]);
+    #[hdl]
+    let out: ReadyValid<T> = m.output(ReadyValid[ty]);
+    #[hdl]
+    let count: UInt = m.output(count_ty);
+
+    #[hdl]
+    let inp_index_reg = reg_builder().clock_domain(cd).reset(0.cast_to(index_ty));
+    #[hdl]
+    let out_index_reg = reg_builder().clock_domain(cd).reset(0.cast_to(index_ty));
+    #[hdl]
+    let maybe_full_reg = reg_builder().clock_domain(cd).reset(false);
+
+    #[hdl]
+    let mut mem = memory(ty);
+    mem.depth(capacity.get());
+    let read_port = mem.new_read_port();
+    let write_port = mem.new_write_port();
+
+    #[hdl]
+    let inp_firing: Bool = wire();
+    connect(inp_firing, ReadyValid::firing(inp));
+    #[hdl]
+    let out_firing: Bool = wire();
+    connect(out_firing, ReadyValid::firing(out));
+    #[hdl]
+    let indexes_equal: Bool = wire();
+    connect(indexes_equal, inp_index_reg.cmp_eq(out_index_reg));
+    #[hdl]
+    let empty: Bool = wire();
+    connect(empty, indexes_equal & !maybe_full_reg);
+    #[hdl]
+    let full: Bool = wire();
+    connect(full, indexes_equal & maybe_full_reg);
+
+    connect(read_port.addr, out_index_reg);
+    connect(read_port.en, true);
+    connect(read_port.clk, cd.clk);
+    connect(write_port.addr, inp_index_reg);
+    connect(write_port.en, inp_firing);
+    connect(write_port.clk, cd.clk);
+    connect(write_port.data, HdlOption::unwrap_or(inp.data, ty.uninit()));
+    connect(write_port.mask, splat_mask(ty, true.to_expr()));
+
+    connect(inp.ready, !full);
+    if inp_ready_is_comb {
+        #[hdl]
+        if out.ready {
+            connect(inp.ready, true);
+        }
+    }
+
+    #[hdl]
+    if !empty {
+        connect(out.data, HdlSome(read_port.data));
+    } else {
+        if out_valid_is_comb {
+            connect(out.data, inp.data);
+        } else {
+            connect(out.data, HdlOption[ty].HdlNone());
+        }
+    }
+
+    #[hdl]
+    if inp_firing.cmp_ne(out_firing) {
+        connect(maybe_full_reg, inp_firing);
+    }
+
+    #[hdl]
+    if inp_firing {
+        #[hdl]
+        if inp_index_reg.cmp_eq(capacity.get() - 1) {
+            connect_any(inp_index_reg, 0_hdl_u0);
+        } else {
+            connect_any(inp_index_reg, inp_index_reg + 1_hdl_u1);
+        }
+    }
+
+    #[hdl]
+    if out_firing {
+        #[hdl]
+        if out_index_reg.cmp_eq(capacity.get() - 1) {
+            connect_any(out_index_reg, 0_hdl_u0);
+        } else {
+            connect_any(out_index_reg, out_index_reg + 1_hdl_u1);
+        }
+    }
+
+    #[hdl]
+    if indexes_equal {
+        #[hdl]
+        if maybe_full_reg {
+            connect_any(count, capacity);
+        } else {
+            connect_any(count, 0_hdl_u0);
+        }
+    } else {
+        if capacity.is_power_of_two() {
+            debug_assert_eq!(count_ty.width(), index_ty.width() + 1);
+            #[hdl]
+            let count_lower = wire(index_ty);
+            connect(
+                count_lower,
+                (inp_index_reg - out_index_reg).cast_to(index_ty),
+            ); // wrap
+            connect(count, count_lower.cast_to(count_ty));
+        } else {
+            debug_assert_eq!(count_ty.width(), index_ty.width());
+            #[hdl]
+            if inp_index_reg.cmp_lt(out_index_reg) {
+                connect(count, inp_index_reg + capacity - out_index_reg);
+            } else {
+                connect(count, inp_index_reg - out_index_reg);
+            }
+        }
+    }
+    // These debug ports expose some internal state during the Induction phase
+    // of Formal Verification. They are not present in normal use.
+    #[cfg(test)]
+    {
+        #[hdl]
+        let dbg: QueueDebugPort<T, UInt> = m.output(QueueDebugPort[ty][index_ty]);
+        // read the memory word currently stored at some fixed index
+        let debug_port = mem.new_read_port();
+        connect(debug_port.addr, dbg.index_to_check);
+        connect(debug_port.en, true);
+        connect(debug_port.clk, cd.clk);
+        connect(dbg.stored, debug_port.data);
+        // also expose the current read and write indices
+        connect(dbg.inp_index, inp_index_reg);
+        connect(dbg.out_index, out_index_reg);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        cli::FormalMode, firrtl::ExportOptions,
+        module::transform::simplify_enums::SimplifyEnumsKind, testing::assert_formal,
+        ty::StaticType,
+    };
+    use std::num::NonZero;
+
+    #[track_caller]
+    fn test_queue(capacity: NonZeroUsize, inp_ready_is_comb: bool, out_valid_is_comb: bool) {
+        assert_formal(
+            format_args!("test_queue_{capacity}_{inp_ready_is_comb}_{out_valid_is_comb}"),
+            queue_test(capacity, inp_ready_is_comb, out_valid_is_comb),
+            FormalMode::Prove,
+            2,
+            None,
+            ExportOptions {
+                simplify_enums: Some(SimplifyEnumsKind::ReplaceWithBundleOfUInts),
+                ..ExportOptions::default()
+            },
+        );
+        /// Formal verification of the FIFO queue
+        ///
+        /// The strategy derives from the observation that, if we filter its
+        /// input and output streams to consider just one in every N reads and
+        /// writes (where N is the FIFO capacity), then the FIFO effectively
+        /// behaves as a one-entry FIFO.
+        ///
+        /// In particular, any counterexample of the full FIFO behaving badly
+        /// will also be caught by one of the filtered versions (one which
+        /// happens to be in phase with the offending input or output).
+        #[hdl_module]
+        fn queue_test(capacity: NonZeroUsize, inp_ready_is_comb: bool, out_valid_is_comb: bool) {
+            #[hdl]
+            let clk: Clock = m.input();
+            #[hdl]
+            let cd = wire();
+            connect(
+                cd,
+                #[hdl]
+                ClockDomain {
+                    clk,
+                    rst: formal_reset().to_reset(),
+                },
+            );
+
+            // random input data
+            #[hdl]
+            let inp_data: HdlOption<UInt<8>> = wire();
+            #[hdl]
+            if any_seq(Bool) {
+                connect(inp_data, HdlSome(any_seq(UInt::<8>::TYPE)));
+            } else {
+                connect(inp_data, HdlNone());
+            }
+
+            // assert output ready at random
+            #[hdl]
+            let out_ready: Bool = wire();
+            connect(out_ready, any_seq(Bool));
+
+            // The current number of elements in the FIFO ranges from zero to
+            // maximum capacity, inclusive.
+            let count_ty = UInt::range_inclusive(0..=capacity.get());
+            // type for counters that wrap around at the FIFO capacity
+            let index_ty = UInt::range(0..capacity.get());
+
+            // among all entries of the FIFO internal circular memory, choose
+            // one at random to check
+            #[hdl]
+            let index_to_check = wire(index_ty);
+            connect(index_to_check, any_const(index_ty));
+            hdl_assume(clk, index_to_check.cmp_lt(capacity.get()), "");
+
+            // instantiate and connect the queue
+            #[hdl]
+            let dut = instance(queue(
+                UInt[ConstUsize::<8>],
+                capacity,
+                inp_ready_is_comb,
+                out_valid_is_comb,
+            ));
+            connect(dut.cd, cd);
+            connect(dut.inp.data, inp_data);
+            connect(dut.out.ready, out_ready);
+
+            // Keep an independent count of words in the FIFO. Ensure that
+            // it's always correct, and never overflows.
+            #[hdl]
+            let expected_count_reg = reg_builder().clock_domain(cd).reset(count_ty.zero());
+            #[hdl]
+            if ReadyValid::firing(dut.inp) & !ReadyValid::firing(dut.out) {
+                hdl_assert(clk, expected_count_reg.cmp_ne(capacity.get()), "");
+                connect_any(expected_count_reg, expected_count_reg + 1u8);
+            } else if !ReadyValid::firing(dut.inp) & ReadyValid::firing(dut.out) {
+                hdl_assert(clk, expected_count_reg.cmp_ne(count_ty.zero()), "");
+                connect_any(expected_count_reg, expected_count_reg - 1u8);
+            }
+            hdl_assert(clk, expected_count_reg.cmp_eq(dut.count), "");
+
+            // keep an independent write index into the FIFO's circular buffer
+            #[hdl]
+            let inp_index_reg = reg_builder().clock_domain(cd).reset(index_ty.zero());
+            #[hdl]
+            if ReadyValid::firing(dut.inp) {
+                #[hdl]
+                if inp_index_reg.cmp_ne(capacity.get() - 1) {
+                    connect_any(inp_index_reg, inp_index_reg + 1u8);
+                } else {
+                    connect_any(inp_index_reg, 0_hdl_u0);
+                }
+            }
+
+            // keep an independent read index into the FIFO's circular buffer
+            #[hdl]
+            let out_index_reg = reg_builder().clock_domain(cd).reset(index_ty.zero());
+            #[hdl]
+            if ReadyValid::firing(dut.out) {
+                #[hdl]
+                if out_index_reg.cmp_ne(capacity.get() - 1) {
+                    connect_any(out_index_reg, out_index_reg + 1u8);
+                } else {
+                    connect_any(out_index_reg, 0_hdl_u0);
+                }
+            }
+
+            // filter the input data stream, predicated by the read index
+            // matching the chosen position in the FIFO's circular buffer
+            #[hdl]
+            let inp_index_matches = wire();
+            connect(inp_index_matches, inp_index_reg.cmp_eq(index_to_check));
+            #[hdl]
+            let inp_firing_data = wire();
+            connect(inp_firing_data, HdlNone());
+            #[hdl]
+            if inp_index_matches {
+                connect(inp_firing_data, ReadyValid::firing_data(dut.inp));
+            }
+
+            // filter the output data stream, predicated by the write index
+            // matching the chosen position in the FIFO's circular buffer
+            #[hdl]
+            let out_index_matches = wire();
+            connect(out_index_matches, out_index_reg.cmp_eq(index_to_check));
+            #[hdl]
+            let out_firing_data = wire();
+            connect(out_firing_data, HdlNone());
+            #[hdl]
+            if out_index_matches {
+                connect(out_firing_data, ReadyValid::firing_data(dut.out));
+            }
+
+            // Implement a one-entry FIFO and ensure its equivalence to the
+            // filtered FIFO.
+            //
+            // the holding register for our one-entry FIFO
+            #[hdl]
+            let stored_reg = reg_builder().clock_domain(cd).reset(HdlNone());
+            #[hdl]
+            match stored_reg {
+                // If the holding register is empty...
+                HdlNone => {
+                    #[hdl]
+                    match inp_firing_data {
+                        // ... and we are not receiving data, then we must not
+                        // transmit any data.
+                        HdlNone => hdl_assert(clk, HdlOption::is_none(out_firing_data), ""),
+                        // If we are indeed receiving some data...
+                        HdlSome(data_in) => {
+                            #[hdl]
+                            match out_firing_data {
+                                // ... and transmitting at the same time, we
+                                // must be transmitting the input data itself,
+                                // since the holding register is empty.
+                                HdlSome(data_out) => hdl_assert(clk, data_out.cmp_eq(data_in), ""),
+                                // If we are receiving, but not transmitting,
+                                // store the received data in the holding
+                                // register.
+                                HdlNone => connect(stored_reg, HdlSome(data_in)),
+                            }
+                        }
+                    }
+                }
+                // If there is some value stored in the holding register...
+                HdlSome(stored) => {
+                    #[hdl]
+                    match out_firing_data {
+                        // ... and we are not transmitting it, we cannot
+                        // receive any more data.
+                        HdlNone => hdl_assert(clk, HdlOption::is_none(inp_firing_data), ""),
+                        // If we are transmitting a previously stored value...
+                        HdlSome(data_out) => {
+                            // ... it must be the same data we stored earlier.
+                            hdl_assert(clk, data_out.cmp_eq(stored), "");
+                            // Also, accept new data, if any. Otherwise,
+                            // let the holding register become empty.
+                            connect(stored_reg, inp_firing_data);
+                        }
+                    }
+                }
+            }
+
+            // from now on, some extra assertions in order to pass induction
+
+            // sync the holding register, when it's occupied, to the
+            // corresponding entry in the FIFO's circular buffer
+            connect(dut.dbg.index_to_check, index_to_check);
+            #[hdl]
+            if let HdlSome(stored) = stored_reg {
+                hdl_assert(clk, stored.cmp_eq(dut.dbg.stored), "");
+            }
+
+            // sync the read and write indices
+            hdl_assert(clk, inp_index_reg.cmp_eq(dut.dbg.inp_index), "");
+            hdl_assert(clk, out_index_reg.cmp_eq(dut.dbg.out_index), "");
+
+            // the indices should never go past the capacity, but induction
+            // doesn't know that...
+            hdl_assert(clk, inp_index_reg.cmp_lt(capacity.get()), "");
+            hdl_assert(clk, out_index_reg.cmp_lt(capacity.get()), "");
+
+            // strongly constrain the state of the holding register
+            //
+            // The holding register is full if and only if the corresponding
+            // FIFO entry was written to and not yet read. In other words, if
+            // the number of pending reads until the chosen entry is read out
+            // is greater than the current FIFO count, then the entry couldn't
+            // be in the FIFO in the first place.
+            #[hdl]
+            let pending_reads: UInt = wire(index_ty);
+            // take care of wrap-around when subtracting indices, add the
+            // capacity amount to keep the result positive if necessary
+            #[hdl]
+            if index_to_check.cmp_ge(out_index_reg) {
+                connect(pending_reads, index_to_check - out_index_reg);
+            } else {
+                connect(
+                    pending_reads,
+                    index_to_check + capacity.get() - out_index_reg,
+                );
+            }
+            // check whether the chosen entry is in the FIFO
+            #[hdl]
+            let expected_stored: Bool = wire();
+            connect(expected_stored, pending_reads.cmp_lt(dut.count));
+            // sync with the state of the holding register
+            hdl_assert(
+                clk,
+                expected_stored.cmp_eq(HdlOption::is_some(stored_reg)),
+                "",
+            );
+        }
+    }
+
+    #[test]
+    fn test_1_false_false() {
+        test_queue(NonZero::new(1).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_1_false_true() {
+        test_queue(NonZero::new(1).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_1_true_false() {
+        test_queue(NonZero::new(1).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_1_true_true() {
+        test_queue(NonZero::new(1).unwrap(), true, true);
+    }
+
+    #[test]
+    fn test_2_false_false() {
+        test_queue(NonZero::new(2).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_2_false_true() {
+        test_queue(NonZero::new(2).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_2_true_false() {
+        test_queue(NonZero::new(2).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_2_true_true() {
+        test_queue(NonZero::new(2).unwrap(), true, true);
+    }
+
+    #[test]
+    fn test_3_false_false() {
+        test_queue(NonZero::new(3).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_3_false_true() {
+        test_queue(NonZero::new(3).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_3_true_false() {
+        test_queue(NonZero::new(3).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_3_true_true() {
+        test_queue(NonZero::new(3).unwrap(), true, true);
+    }
+
+    #[test]
+    fn test_4_false_false() {
+        test_queue(NonZero::new(4).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_4_false_true() {
+        test_queue(NonZero::new(4).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_4_true_false() {
+        test_queue(NonZero::new(4).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_4_true_true() {
+        test_queue(NonZero::new(4).unwrap(), true, true);
+    }
+
+    #[test]
+    fn test_many_false_false() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), false, false);
+    }
+
+    #[test]
+    fn test_many_false_true() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), false, true);
+    }
+
+    #[test]
+    fn test_many_true_false() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), true, false);
+    }
+
+    #[test]
+    fn test_many_true_true() {
+        test_queue(NonZero::new((2 << 16) - 5).unwrap(), true, true);
+    }
+}
--- a/crates/fayalite/src/util/scoped_ref.rs
+++ b/crates/fayalite/src/util/scoped_ref.rs
@ -0,0 +1,114 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+mod safety_boundary {
+    use std::{cell::Cell, ptr::NonNull};
+
+    pub(super) struct Impl<T: ?Sized>(Cell<Option<NonNull<T>>>);
+
+    impl<T: ?Sized> Impl<T> {
+        #[inline]
+        pub(super) const fn new() -> Self {
+            Self(Cell::new(None))
+        }
+        #[inline]
+        pub(super) const fn opt_static_ref(v: Option<&'static T>) -> Self {
+            Self(Cell::new(if let Some(v) = v {
+                // SAFETY: v is a valid reference for lifetime 'static
+                unsafe { Some(NonNull::new_unchecked(v as *const T as *mut T)) }
+            } else {
+                None
+            }))
+        }
+        /// set `self` to `value` for the duration of the `f()` call.
+        #[inline]
+        pub(super) fn set_opt<F: FnOnce() -> R, R>(&self, value: Option<&T>, f: F) -> R {
+            struct ResetOnDrop<'a, T: ?Sized> {
+                this: &'a Impl<T>,
+                old: Option<NonNull<T>>,
+            }
+            impl<T: ?Sized> Drop for ResetOnDrop<'_, T> {
+                fn drop(&mut self) {
+                    self.this.0.set(self.old);
+                }
+            }
+            // reset to old value before exiting this function ensuring `self`
+            // is not set to `value` when its lifetime is expired
+            let _reset_on_drop = ResetOnDrop {
+                this: self,
+                old: self.0.replace(value.map(NonNull::from)),
+            };
+            f()
+        }
+        #[inline]
+        pub(super) fn get_ptr(&self) -> Option<NonNull<T>> {
+            self.0.get()
+        }
+        /// get the reference in `self` for the duration of the `f(...)` call.
+        #[inline]
+        pub(super) fn with_opt<F: for<'a> FnOnce(Option<&'a T>) -> R, R>(&self, f: F) -> R {
+            // SAFETY:
+            // `self.0` is only `Some` when inside some `set_opt` call or when set
+            // to some `&'static T`, which ensures that the pointer is live and valid.
+            //
+            // the reference we give away has its lifetime scoped to this
+            // function call which ensures that it won't escape
+            unsafe { f(self.0.get().map(|v| &*v.as_ptr())) }
+        }
+    }
+}
+
+/// holds a `Cell<Option<&'scoped T>>` where `'scoped` is erased. This is useful for holding references in TLS.
+pub struct ScopedRef<T: ?Sized>(safety_boundary::Impl<T>);
+
+impl<T: ?Sized> ScopedRef<T> {
+    /// create a new empty [`ScopedRef`]
+    #[inline]
+    pub const fn new() -> Self {
+        Self(safety_boundary::Impl::new())
+    }
+    #[inline]
+    pub const fn opt_static_ref(v: Option<&'static T>) -> Self {
+        Self(safety_boundary::Impl::opt_static_ref(v))
+    }
+    #[inline]
+    pub const fn static_ref(v: &'static T) -> Self {
+        Self::opt_static_ref(Some(v))
+    }
+    /// set `self` to `value` for the duration of the `f()` call.
+    #[inline]
+    pub fn set_opt<F: FnOnce() -> R, R>(&self, value: Option<&T>, f: F) -> R {
+        self.0.set_opt(value, f)
+    }
+    /// set `self` to `value` for the duration of the `f()` call.
+    #[inline]
+    pub fn set<F: FnOnce() -> R, R>(&self, value: &T, f: F) -> R {
+        self.0.set_opt(Some(value), f)
+    }
+    #[inline]
+    pub fn is_some(&self) -> bool {
+        self.0.get_ptr().is_some()
+    }
+    #[inline]
+    pub fn is_none(&self) -> bool {
+        self.0.get_ptr().is_none()
+    }
+    /// get the reference in `self` for the duration of the `f(...)` call. panics if no reference is set.
+    #[inline]
+    pub fn with<F: FnOnce(&T) -> R, R>(&self, f: F) -> R {
+        self.0.with_opt(
+            #[inline]
+            |v| f(v.expect("called ScopedRef::with on an empty ScopedRef")),
+        )
+    }
+    /// get the reference in `self` for the duration of the `f(...)` call.
+    #[inline]
+    pub fn with_opt<F: FnOnce(Option<&T>) -> R, R>(&self, f: F) -> R {
+        self.0.with_opt(f)
+    }
+}
+
+impl<T: ?Sized> Default for ScopedRef<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
--- a/crates/fayalite/src/util/streaming_read_utf8.rs
+++ b/crates/fayalite/src/util/streaming_read_utf8.rs
@ -0,0 +1,31 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use std::{
+    io::{self, BufRead},
+    str,
+};
+
+pub(crate) fn streaming_read_utf8<R: BufRead, E: From<io::Error>>(
+    reader: R,
+    mut callback: impl FnMut(&str) -> Result<(), E>,
+) -> Result<(), E> {
+    let mut buf = [0; 4];
+    let mut buf_len = 0;
+    for byte in reader.bytes() {
+        buf[buf_len] = byte?;
+        buf_len += 1;
+        match str::from_utf8(&buf[..buf_len]) {
+            Ok(buf) => {
+                callback(buf)?;
+                buf_len = 0;
+            }
+            Err(e) => {
+                if e.error_len().is_some() {
+                    callback("\u{FFFD}")?; // replacement character
+                    buf_len = 0;
+                }
+            }
+        }
+    }
+    Ok(())
+}
--- a/crates/fayalite/src/util/test_hasher.rs
+++ b/crates/fayalite/src/util/test_hasher.rs
@ -0,0 +1,240 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+#![cfg(feature = "unstable-test-hasher")]
+
+use std::{
+    fmt::Write as _,
+    hash::{BuildHasher, Hash, Hasher},
+    io::Write as _,
+    marker::PhantomData,
+    sync::LazyLock,
+};
+
+type BoxDynHasher = Box<dyn Hasher + Send + Sync>;
+type BoxDynBuildHasher = Box<dyn DynBuildHasherTrait + Send + Sync>;
+type BoxDynMakeBuildHasher = Box<dyn Fn() -> BoxDynBuildHasher + Send + Sync>;
+
+trait TryGetDynBuildHasher: Copy {
+    type Type;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher>;
+}
+
+impl<T> TryGetDynBuildHasher for PhantomData<T> {
+    type Type = T;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher> {
+        None
+    }
+}
+
+impl<T: Default + BuildHasher<Hasher: Send + Sync + 'static> + Send + Sync + 'static + Clone>
+    TryGetDynBuildHasher for &'_ PhantomData<T>
+{
+    type Type = T;
+    fn try_get_make_build_hasher(self) -> Option<BoxDynMakeBuildHasher> {
+        Some(Box::new(|| Box::<DynBuildHasher<T>>::default()))
+    }
+}
+
+#[derive(Default, Clone)]
+struct DynBuildHasher<T>(T);
+
+trait DynBuildHasherTrait: BuildHasher<Hasher = BoxDynHasher> {
+    fn clone_dyn_build_hasher(&self) -> BoxDynBuildHasher;
+}
+
+impl<BH: BuildHasher<Hasher: Send + Sync + 'static>> BuildHasher for DynBuildHasher<BH> {
+    type Hasher = BoxDynHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        Box::new(self.0.build_hasher())
+    }
+
+    fn hash_one<T: Hash>(&self, x: T) -> u64 {
+        self.0.hash_one(x)
+    }
+}
+
+impl<BH> DynBuildHasherTrait for DynBuildHasher<BH>
+where
+    Self: Clone + BuildHasher<Hasher = BoxDynHasher> + Send + Sync + 'static,
+{
+    fn clone_dyn_build_hasher(&self) -> BoxDynBuildHasher {
+        Box::new(self.clone())
+    }
+}
+
+pub struct DefaultBuildHasher(BoxDynBuildHasher);
+
+impl Clone for DefaultBuildHasher {
+    fn clone(&self) -> Self {
+        DefaultBuildHasher(self.0.clone_dyn_build_hasher())
+    }
+}
+
+const ENV_VAR_NAME: &'static str = "FAYALITE_TEST_HASHER";
+
+struct EnvVarValue {
+    key: &'static str,
+    try_get_make_build_hasher: fn() -> Option<BoxDynMakeBuildHasher>,
+    description: &'static str,
+}
+
+macro_rules! env_var_value {
+    (
+        key: $key:literal,
+        build_hasher: $build_hasher:ty,
+        description: $description:literal,
+    ) => {
+        EnvVarValue {
+            key: $key,
+            try_get_make_build_hasher: || {
+                // use rust method resolution to detect if $build_hasher is usable
+                // (e.g. hashbrown's hasher won't be usable without the right feature enabled)
+                (&PhantomData::<DynBuildHasher<$build_hasher>>).try_get_make_build_hasher()
+            },
+            description: $description,
+        }
+    };
+}
+
+#[derive(Default)]
+struct AlwaysZeroHasher;
+
+impl Hasher for AlwaysZeroHasher {
+    fn write(&mut self, _bytes: &[u8]) {}
+    fn finish(&self) -> u64 {
+        0
+    }
+}
+
+const ENV_VAR_VALUES: &'static [EnvVarValue] = &[
+    env_var_value! {
+        key: "std",
+        build_hasher: std::hash::RandomState,
+        description: "use std::hash::RandomState",
+    },
+    env_var_value! {
+        key: "hashbrown",
+        build_hasher: hashbrown::DefaultHashBuilder,
+        description: "use hashbrown's DefaultHashBuilder",
+    },
+    env_var_value! {
+        key: "always_zero",
+        build_hasher: std::hash::BuildHasherDefault<AlwaysZeroHasher>,
+        description: "use a hasher that always returns 0 for all hashes,\n    \
+        this is useful for checking that PartialEq impls are correct",
+    },
+];
+
+fn report_bad_env_var(msg: impl std::fmt::Display) -> ! {
+    let mut msg = format!("{ENV_VAR_NAME}: {msg}\n");
+    for &EnvVarValue {
+        key,
+        try_get_make_build_hasher,
+        description,
+    } in ENV_VAR_VALUES
+    {
+        let availability = match try_get_make_build_hasher() {
+            Some(_) => "available",
+            None => "unavailable",
+        };
+        writeln!(msg, "{key}: ({availability})\n    {description}").expect("can't fail");
+    }
+    std::io::stderr()
+        .write_all(msg.as_bytes())
+        .expect("should be able to write to stderr");
+    std::process::abort();
+}
+
+impl Default for DefaultBuildHasher {
+    fn default() -> Self {
+        static DEFAULT_FN: LazyLock<BoxDynMakeBuildHasher> = LazyLock::new(|| {
+            let var = std::env::var_os(ENV_VAR_NAME);
+            let var = var.as_deref().unwrap_or("std".as_ref());
+            for &EnvVarValue {
+                key,
+                try_get_make_build_hasher,
+                description: _,
+            } in ENV_VAR_VALUES
+            {
+                if var.as_encoded_bytes().eq_ignore_ascii_case(key.as_bytes()) {
+                    return try_get_make_build_hasher().unwrap_or_else(|| {
+                        report_bad_env_var(format_args!(
+                            "unavailable hasher: {key} (is the appropriate feature enabled?)"
+                        ));
+                    });
+                }
+            }
+            report_bad_env_var(format_args!("unrecognized hasher: {var:?}"));
+        });
+        Self(DEFAULT_FN())
+    }
+}
+
+pub struct DefaultHasher(BoxDynHasher);
+
+impl BuildHasher for DefaultBuildHasher {
+    type Hasher = DefaultHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        DefaultHasher(self.0.build_hasher())
+    }
+}
+
+impl Hasher for DefaultHasher {
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        self.0.write(bytes)
+    }
+
+    fn write_u8(&mut self, i: u8) {
+        self.0.write_u8(i)
+    }
+
+    fn write_u16(&mut self, i: u16) {
+        self.0.write_u16(i)
+    }
+
+    fn write_u32(&mut self, i: u32) {
+        self.0.write_u32(i)
+    }
+
+    fn write_u64(&mut self, i: u64) {
+        self.0.write_u64(i)
+    }
+
+    fn write_u128(&mut self, i: u128) {
+        self.0.write_u128(i)
+    }
+
+    fn write_usize(&mut self, i: usize) {
+        self.0.write_usize(i)
+    }
+
+    fn write_i8(&mut self, i: i8) {
+        self.0.write_i8(i)
+    }
+
+    fn write_i16(&mut self, i: i16) {
+        self.0.write_i16(i)
+    }
+
+    fn write_i32(&mut self, i: i32) {
+        self.0.write_i32(i)
+    }
+
+    fn write_i64(&mut self, i: i64) {
+        self.0.write_i64(i)
+    }
+
+    fn write_i128(&mut self, i: i128) {
+        self.0.write_i128(i)
+    }
+
+    fn write_isize(&mut self, i: isize) {
+        self.0.write_isize(i)
+    }
+}
--- a/crates/fayalite/src/valueless.rs
+++ b/crates/fayalite/src/valueless.rs
@ -1,88 +0,0 @@
-// SPDX-License-Identifier: LGPL-3.0-or-later
-// See Notices.txt for copyright information
-use crate::{
-    int::{DynIntType, DynSIntType, DynUIntType, IntTypeTrait, SIntType},
-    ty::{Type, Value},
-};
-use std::ops::RangeBounds;
-
-#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq, Default)]
-pub struct Valueless<T> {
-    pub ty: T,
-}
-
-impl<T: Type> Valueless<T> {
-    pub fn to_canonical(&self) -> Valueless<T::CanonicalType> {
-        Valueless {
-            ty: self.ty.canonical(),
-        }
-    }
-    pub fn from_canonical(v: Valueless<T::CanonicalType>) -> Self {
-        Valueless {
-            ty: T::from_canonical_type(v.ty),
-        }
-    }
-}
-
-mod sealed {
-    pub trait Sealed {}
-}
-
-pub trait ValuelessTr: sealed::Sealed {
-    type Type: Type<Value = Self::Value>;
-    type Value: Value<Type = Self::Type>;
-}
-
-impl<T> sealed::Sealed for Valueless<T> {}
-
-impl<T: Type> ValuelessTr for Valueless<T> {
-    type Type = T;
-    type Value = T::Value;
-}
-
-impl<T: IntTypeTrait> Valueless<T> {
-    pub fn signum(&self) -> Valueless<SIntType<2>> {
-        Valueless::default()
-    }
-    pub fn as_same_width_uint(self) -> Valueless<T::SameWidthUInt> {
-        Valueless {
-            ty: self.ty.as_same_width_uint(),
-        }
-    }
-    pub fn as_same_width_sint(self) -> Valueless<T::SameWidthSInt> {
-        Valueless {
-            ty: self.ty.as_same_width_sint(),
-        }
-    }
-    pub fn as_same_value_uint(self) -> Valueless<DynUIntType> {
-        Valueless {
-            ty: self.ty.as_same_value_uint(),
-        }
-    }
-    pub fn as_same_value_sint(self) -> Valueless<DynSIntType> {
-        Valueless {
-            ty: self.ty.as_same_value_sint(),
-        }
-    }
-    pub fn concat<HighType: IntTypeTrait>(
-        &self,
-        high_part: Valueless<HighType>,
-    ) -> Valueless<DynIntType<HighType::Signed>> {
-        let ty = DynIntType::new(
-            self.ty
-                .width()
-                .checked_add(high_part.ty.width())
-                .expect("result has too many bits"),
-        );
-        Valueless { ty }
-    }
-    pub fn repeat(&self, count: usize) -> Valueless<DynIntType<T::Signed>> {
-        let width = self.ty.width();
-        let ty = DynIntType::new(width.checked_mul(count).expect("result has too many bits"));
-        Valueless { ty }
-    }
-    pub fn slice<I: RangeBounds<usize>>(&self, index: I) -> Valueless<DynUIntType> {
-        let ty = self.ty.slice(index);
-        Valueless { ty }
-    }
-}
--- a/crates/fayalite/src/wire.rs
+++ b/crates/fayalite/src/wire.rs
@ -1,15 +1,15 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    expr::{Expr, ExprTrait, Flow, ToExpr},
+    expr::{Expr, Flow, ToExpr},
    intern::Interned,
-    module::{NameId, ScopedNameId},
+    module::{IncompleteDeclaration, NameId, ScopedNameId, StmtDeclaration, StmtWire},
    source_location::SourceLocation,
-    ty::{DynCanonicalType, DynType, Type},
+    ty::{CanonicalType, Type},
 };
-use std::fmt;
+use std::{cell::RefCell, fmt, rc::Rc};

-#[derive(Clone, Eq, PartialEq, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Wire<T: Type> {
    name: ScopedNameId,
    source_location: SourceLocation,
@ -18,27 +18,14 @@ pub struct Wire<T: Type> {

 impl<T: Type + fmt::Debug> fmt::Debug for Wire<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("Wire")
-            .field("name", &self.name)
-            .field("ty", &self.ty)
-            .finish_non_exhaustive()
-    }
-}
-
-impl<T: Type> ToExpr for Wire<T> {
-    type Type = T;
-
-    fn ty(&self) -> Self::Type {
-        self.ty.clone()
-    }
-
-    fn to_expr(&self) -> Expr<<Self::Type as Type>::Value> {
-        Expr::new_unchecked(self.expr_enum())
+        write!(f, "Wire({:?}: ", self.name)?;
+        self.ty.fmt(f)?;
+        f.write_str(")")
    }
 }

 impl<T: Type> Wire<T> {
-    pub fn canonical(&self) -> Wire<T::CanonicalType> {
+    pub fn canonical(&self) -> Wire<CanonicalType> {
        let Self {
            name,
            source_location,
@ -50,29 +37,20 @@ impl<T: Type> Wire<T> {
            ty: ty.canonical(),
        }
    }
-    pub fn to_dyn_wire(&self) -> Wire<Interned<dyn DynType>> {
-        let Self {
+    pub fn from_canonical(v: Wire<CanonicalType>) -> Self {
+        let Wire {
            name,
            source_location,
-            ref ty,
-        } = *self;
-        Wire {
+            ty,
+        } = v;
+        Self {
            name,
            source_location,
-            ty: ty.to_dyn(),
+            ty: T::from_canonical(ty),
        }
    }
-    pub fn to_dyn_canonical_wire(&self) -> Wire<Interned<dyn DynCanonicalType>> {
-        let Self {
-            name,
-            source_location,
-            ref ty,
-        } = *self;
-        Wire {
-            name,
-            source_location,
-            ty: ty.canonical_dyn(),
-        }
+    pub fn ty(&self) -> T {
+        self.ty
    }
    pub fn new_unchecked(
        scoped_name: ScopedNameId,
@ -110,3 +88,57 @@ impl<T: Type> Wire<T> {
        true
    }
 }
+
+#[derive(Clone)]
+pub struct IncompleteWire {
+    pub(crate) declaration: Rc<RefCell<IncompleteDeclaration>>,
+}
+
+impl IncompleteWire {
+    #[track_caller]
+    pub fn complete<T: Type>(&mut self, ty: T) -> Expr<T> {
+        let canonical_type = ty.canonical();
+        let mut declaration = self.declaration.borrow_mut();
+        if let IncompleteDeclaration::Incomplete {
+            name,
+            source_location,
+        } = *declaration
+        {
+            *declaration = IncompleteDeclaration::Complete(
+                StmtWire {
+                    annotations: (),
+                    wire: Wire {
+                        name,
+                        source_location,
+                        ty: canonical_type,
+                    },
+                }
+                .into(),
+            );
+        }
+        match *declaration {
+            IncompleteDeclaration::Complete(StmtDeclaration::Wire(StmtWire {
+                wire:
+                    Wire {
+                        name,
+                        source_location,
+                        ty: wire_ty,
+                    },
+                ..
+            })) => {
+                drop(declaration);
+                assert_eq!(wire_ty, canonical_type, "type mismatch");
+                Wire {
+                    name,
+                    source_location,
+                    ty,
+                }
+                .to_expr()
+            }
+            IncompleteDeclaration::Taken => panic!("can't use wire outside of containing module"),
+            IncompleteDeclaration::Complete(_) | IncompleteDeclaration::Incomplete { .. } => {
+                unreachable!()
+            }
+        }
+    }
+}
--- a/crates/fayalite/tests/formal.rs
+++ b/crates/fayalite/tests/formal.rs
@ -0,0 +1,295 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+//! Formal tests in Fayalite
+
+use fayalite::{
+    cli::FormalMode,
+    clock::{Clock, ClockDomain},
+    expr::{CastTo, HdlPartialEq},
+    firrtl::ExportOptions,
+    formal::{any_const, any_seq, formal_reset, hdl_assert, hdl_assume},
+    hdl, hdl_module,
+    int::{Bool, DynSize, Size, UInt, UIntType},
+    module::{connect, connect_any, instance, memory, reg_builder, wire},
+    reset::ToReset,
+    testing::assert_formal,
+    ty::StaticType,
+};
+
+/// Test hidden state
+///
+/// Hidden state can cause problems for induction, since the formal engine
+/// can assign invalid values to the state registers, making it traverse
+/// valid but unreachable states.
+///
+/// One solution is to go sufficiently in the past so the engine is forced
+/// to eventually take a reachable state. This may be hampered by
+/// existence of loops, then assumptions may be added to break them.
+///
+/// Another solution is to "open the black box" and add additional
+/// assertions involving the hidden state, so that the unreachable states
+/// become invalid as well.
+///
+/// Both approaches are taken here.
+///
+/// See [Claire Wolf's presentation] and [Zipcpu blog article].
+///
+/// [Claire Wolf's presentation]: https://web.archive.org/web/20200115081517fw_/http://www.clifford.at/papers/2017/smtbmc-sby/
+/// [Zipcpu blog article]: https://zipcpu.com/blog/2018/03/10/induction-exercise.html
+mod hidden_state {
+    use super::*;
+    /// Test hidden state by shift registers
+    ///
+    /// The code implement the ideas from an article in the [Zipcpu blog]. Two
+    /// shift registers are fed from the same input, so they should always have
+    /// the same value. However the only observable is a comparison of their
+    /// last bit, all the others are hidden. To complicate matters, an enable
+    /// signal causes a loop in state space.
+    ///
+    /// [Zipcpu blog]: https://zipcpu.com/blog/2018/03/10/induction-exercise.html
+    #[test]
+    fn shift_register() {
+        enum ConstraintMode {
+            WithExtraAssertions,
+            WithExtraAssumptions,
+        }
+        use ConstraintMode::*;
+        #[hdl_module]
+        fn test_module(constraint_mode: ConstraintMode) {
+            #[hdl]
+            let clk: Clock = m.input();
+            #[hdl]
+            let cd = wire();
+            connect(
+                cd,
+                #[hdl]
+                ClockDomain {
+                    clk,
+                    rst: formal_reset().to_reset(),
+                },
+            );
+            // input signal for the shift registers
+            #[hdl]
+            let i: Bool = wire();
+            connect(i, any_seq(Bool));
+            // shift enable signal
+            #[hdl]
+            let en: Bool = wire();
+            connect(en, any_seq(Bool));
+            // comparison output
+            #[hdl]
+            let o: Bool = wire();
+            // shift registers, with enable
+            #[hdl]
+            let r1 = reg_builder().clock_domain(cd).reset(0u8);
+            #[hdl]
+            let r2 = reg_builder().clock_domain(cd).reset(0u8);
+            #[hdl]
+            if en {
+                connect_any(r1, (r1 << 1) | i.cast_to(UInt[1]));
+                connect_any(r2, (r2 << 1) | i.cast_to(UInt[1]));
+            }
+            // compare last bits of both shift registers
+            connect(o, r1[7].cmp_eq(r2[7]));
+
+            // what we want to prove: last bits are always equal
+            hdl_assert(clk, o, "");
+
+            // additional terms below are only needed to assist with the induction proof
+            match constraint_mode {
+                WithExtraAssertions => {
+                    // "Open the box": add assertions about hidden state.
+                    // In this case, the hidden bits are also always equal.
+                    hdl_assert(clk, r1.cmp_eq(r2), "");
+                }
+                WithExtraAssumptions => {
+                    // Break the loop, do not allow "en" to remain low forever
+                    #[hdl]
+                    let past_en_reg = reg_builder().clock_domain(cd).reset(false);
+                    connect(past_en_reg, en);
+                    hdl_assume(clk, past_en_reg | en, "");
+                }
+            }
+        }
+        // we need a minimum of 16 steps so we can constrain all eight shift register bits,
+        // given that we are allowed to disable the shift once every two cycles.
+        assert_formal(
+            "shift_register_with_assumptions",
+            test_module(WithExtraAssumptions),
+            FormalMode::Prove,
+            16,
+            None,
+            ExportOptions::default(),
+        );
+        // here a couple of cycles is enough
+        assert_formal(
+            "shift_register_with_assertions",
+            test_module(WithExtraAssertions),
+            FormalMode::Prove,
+            2,
+            None,
+            ExportOptions::default(),
+        );
+    }
+}
+
+/// Formal verification of designs containing memories
+///
+/// There is a trick for memories, described in the [Zipcpu blog].
+/// First, select a fixed but arbitrary memory address, monitoring all reads
+/// and writes made to it. Then, assert that anything read from that location
+/// matches the last stored value.
+///
+/// A difficulty for induction is that the memory represents [hidden_state]. A
+/// solution is to include an additional read port to the memory and assert
+/// that the memory location effectively contains the last stored value.
+/// This additional debug port is present only to assist the proof and is
+/// unused (optimized out) in actual use.
+///
+/// [Zipcpu blog]: <https://zipcpu.com/zipcpu/2018/07/13/memories.html>
+mod memory {
+    use super::*;
+
+    /// Test a simple 8-bit SRAM model
+    #[test]
+    fn test_sram() {
+        #[hdl]
+        struct WritePort<AddrWidth: Size> {
+            addr: UIntType<AddrWidth>,
+            data: UInt<8>,
+            en: Bool,
+        }
+        #[hdl]
+        struct ReadPort<AddrWidth: Size> {
+            addr: UIntType<AddrWidth>,
+            #[hdl(flip)]
+            data: UInt<8>,
+        }
+        /// This debug port is only meant to assist the proof.
+        /// For normal use in a design, a wrapper could be provided,
+        /// omitting this port.
+        /// The implementation is forbidden to use any information
+        /// provided on this port in its internal workings.
+        #[hdl]
+        struct DebugPort<AddrWidth: Size> {
+            selected: UIntType<AddrWidth>,
+            stored: UInt<8>,
+            wrote: Bool,
+        }
+        /// simple 1R1W SRAM model (one asynchronous read port and one
+        /// independent write port) with `n`-bit address width
+        #[hdl_module]
+        fn example_sram(n: usize) {
+            #[hdl]
+            let wr: WritePort<DynSize> = m.input(WritePort[n]);
+            #[hdl]
+            let rd: ReadPort<DynSize> = m.input(ReadPort[n]);
+            #[hdl]
+            let cd: ClockDomain = m.input();
+
+            // declare and connect the backing memory
+            #[hdl]
+            let mut mem = memory();
+            mem.depth(1 << n);
+            let read_port = mem.new_read_port();
+            let write_port = mem.new_write_port();
+            connect(write_port.clk, cd.clk);
+            connect(write_port.addr, wr.addr);
+            connect(write_port.en, wr.en);
+            connect(write_port.data, wr.data);
+            connect(write_port.mask, true);
+            connect(read_port.clk, cd.clk);
+            connect(read_port.addr, rd.addr);
+            connect(read_port.en, true);
+            connect(rd.data, read_port.data);
+
+            // To assist with induction, ensure that the chosen memory location
+            // really contains, always, the last value written to it.
+            #[hdl]
+            let dbg: DebugPort<DynSize> = m.input(DebugPort[n]);
+            let debug_port = mem.new_read_port();
+            connect(debug_port.en, true);
+            connect(debug_port.clk, cd.clk);
+            connect(debug_port.addr, dbg.selected);
+            #[hdl]
+            if dbg.wrote {
+                hdl_assert(cd.clk, debug_port.data.cmp_eq(dbg.stored), "");
+                // Try commenting out the assert above, induction will fail.
+                // Opening the trace, it can be seen that the memory contents
+                // and the stored value don't match, which is an unreachable
+                // state. By asserting the above, it will become invalid
+                // as well, so induction will skip this kind of situation.
+            }
+        }
+
+        /// formal verification of the SRAM module, parametrized by the
+        /// address bit-width
+        #[hdl_module]
+        fn test_module(n: usize) {
+            #[hdl]
+            let clk: Clock = m.input();
+            let cd = #[hdl]
+            ClockDomain {
+                clk,
+                rst: formal_reset().to_reset(),
+            };
+
+            // instantiate the SRAM model, connecting its inputs to
+            // a random sequence
+            #[hdl]
+            let rd: ReadPort<DynSize> = wire(ReadPort[n]);
+            connect(rd.addr, any_seq(UInt[n]));
+            #[hdl]
+            let wr: WritePort<DynSize> = wire(WritePort[n]);
+            connect(wr.addr, any_seq(UInt[n]));
+            connect(wr.data, any_seq(UInt::<8>::TYPE));
+            connect(wr.en, any_seq(Bool));
+            #[hdl]
+            let dut = instance(example_sram(n));
+            connect(dut.cd, cd);
+            connect(dut.rd, rd);
+            connect(dut.wr, wr);
+
+            // select a fixed but arbitrary test address
+            #[hdl]
+            let selected = wire(UInt[n]);
+            connect(selected, any_const(UInt[n]));
+            // store the last value written to that address
+            #[hdl]
+            let stored: UInt<8> = reg_builder().clock_domain(cd).reset(0u8);
+            // since memories are not initialized, track whether we wrote to the
+            // memory at least once
+            #[hdl]
+            let wrote: Bool = reg_builder().clock_domain(cd).reset(false);
+            // on a write, capture the last written value
+            #[hdl]
+            if wr.en & wr.addr.cmp_eq(selected) {
+                connect(stored, wr.data);
+                connect(wrote, true);
+            }
+            // on a read, assert that the read value is the same which was stored
+            #[hdl]
+            if rd.addr.cmp_eq(selected) & wrote {
+                hdl_assert(clk, rd.data.cmp_eq(stored), "");
+            }
+
+            // to assist induction, pass our state to the underlying instance
+            let dbg = #[hdl]
+            DebugPort {
+                selected,
+                stored,
+                wrote,
+            };
+            connect(dut.dbg, dbg);
+        }
+
+        assert_formal(
+            "sram",
+            test_module(8),
+            FormalMode::Prove,
+            2,
+            None,
+            ExportOptions::default(),
+        );
+    }
+}
--- a/crates/fayalite/tests/hdl_types.rs
+++ b/crates/fayalite/tests/hdl_types.rs
@ -0,0 +1,199 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use fayalite::{
+    bundle::BundleType,
+    enum_::EnumType,
+    int::{BoolOrIntType, IntType},
+    phantom_const::PhantomConst,
+    prelude::*,
+    ty::StaticType,
+};
+use std::marker::PhantomData;
+
+#[hdl(outline_generated)]
+pub struct MyConstSize<V: Size> {
+    pub size: PhantomConst<UIntType<V>>,
+}
+
+#[hdl(outline_generated)]
+pub struct S<T, Len: Size, T2> {
+    pub a: T,
+    b: UInt<3>,
+    pub(crate) c: ArrayType<UInt<1>, Len>,
+    pub d: T2,
+    pub _phantom: PhantomData<(T, Len)>,
+}
+
+#[hdl(outline_generated)]
+pub struct S3<const LEN: usize, T> {
+    pub a: T,
+    b: UInt<3>,
+    pub(crate) c: Array<UInt<1>, LEN>,
+    pub d: S<T, ConstUsize<LEN>, ()>,
+}
+
+#[hdl(outline_generated)]
+pub enum E<T> {
+    A,
+    B(UInt<3>),
+    C(T),
+    D(TyAlias2),
+    E(TyAlias<Bool, ConstUsize<1>, { 1 + 2 }>),
+}
+
+#[hdl(outline_generated)]
+pub struct S2<T = ()> {
+    pub v: E<T>,
+}
+
+#[hdl(outline_generated)]
+pub type TyAlias<T, Sz: Size, const C: usize, D = ()> = Array<S<T, Sz, D>, C>;
+
+#[hdl(outline_generated)]
+pub type TyAlias2 = TyAlias<UInt<8>, ConstUsize<24>, 5>;
+
+// check that #[hdl] properly handles hygiene
+macro_rules! types_in_macros {
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident, $B:ident, $C:ident, $D:ident, $E:ident, $F:ident) => {
+        #[hdl]
+        struct $F {}
+        #[hdl]
+        struct $A<$B, $C: Size, const $D: usize, $E = $F> {
+            $a: $B,
+            $b: UIntType<$C>,
+            $c: SInt<$D>,
+            $d: HdlOption<$E>,
+            $e: $E,
+            $f: $F,
+        }
+        #[allow(non_camel_case_types)]
+        #[hdl]
+        enum $B<$C: Size, const $D: usize, $E = $F> {
+            $a($A<(), $C, $D, $E>),
+            $b(UIntType<$C>),
+            $c(SInt<$D>),
+            $d,
+            $e($E),
+            $f($F),
+        }
+    };
+    // ensure every identifier has different hygiene
+    () => {
+        types_in_macros!(a);
+    };
+    ($a:ident) => {
+        types_in_macros!($a, b);
+    };
+    ($a:ident, $b:ident) => {
+        types_in_macros!($a, $b, c);
+    };
+    ($a:ident, $b:ident, $c:ident) => {
+        types_in_macros!($a, $b, $c, d);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident) => {
+        types_in_macros!($a, $b, $c, $d, e);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, f);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, A);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, $A, B);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident, $B:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, $A, $B, C);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident, $B:ident, $C:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, $A, $B, $C, D);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident, $B:ident, $C:ident, $D:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, $A, $B, $C, $D, E);
+    };
+    ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident, $f:ident, $A:ident, $B:ident, $C:ident, $D:ident, $E:ident) => {
+        types_in_macros!($a, $b, $c, $d, $e, $f, $A, $B, $C, $D, $E, F);
+    };
+}
+
+types_in_macros!();
+
+mod bound_kind {
+    use fayalite::prelude::*;
+
+    #[hdl]
+    pub struct Type<T> {
+        v: T,
+    }
+
+    #[hdl]
+    pub struct Size<T: ::fayalite::int::Size> {
+        v: UIntType<T>,
+    }
+}
+
+macro_rules! check_bounds {
+    ($name:ident<$(#[$field:ident, $kind:ident] $var:ident: $($bound:ident +)*),*>) => {
+        #[hdl(outline_generated)]
+        struct $name<$($var: $($bound +)*,)*> {
+            $($field: bound_kind::$kind<$var>,)*
+        }
+    };
+}
+
+check_bounds!(CheckBoundsS0<#[a, Size] A: Size +>);
+check_bounds!(CheckBoundsS1<#[a, Size] A: KnownSize +>);
+check_bounds!(CheckBoundsT0<#[a, Type] A: Type +>);
+check_bounds!(CheckBoundsT1<#[a, Type] A: BoolOrIntType +>);
+check_bounds!(CheckBoundsT2<#[a, Type] A: BundleType +>);
+check_bounds!(CheckBoundsT3<#[a, Type] A: EnumType +>);
+check_bounds!(CheckBoundsT4<#[a, Type] A: IntType +>);
+check_bounds!(CheckBoundsT5<#[a, Type] A: StaticType +>);
+check_bounds!(CheckBoundsSS0<#[a, Size] A: Size +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsSS1<#[a, Size] A: KnownSize +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsST0<#[a, Size] A: Size +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsST1<#[a, Size] A: KnownSize +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTS0<#[a, Type] A: Type +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTS1<#[a, Type] A: BoolOrIntType +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTS2<#[a, Type] A: BundleType +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTS3<#[a, Type] A: EnumType +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTS4<#[a, Type] A: IntType +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTS5<#[a, Type] A: StaticType +, #[b, Size] B: Size +>);
+check_bounds!(CheckBoundsTT0<#[a, Type] A: Type +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTT1<#[a, Type] A: BoolOrIntType +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTT2<#[a, Type] A: BundleType +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTT3<#[a, Type] A: EnumType +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTT4<#[a, Type] A: IntType +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsTT5<#[a, Type] A: StaticType +, #[b, Type] B: Type +>);
+check_bounds!(CheckBoundsSSS0<#[a, Size] A: Size +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsSSS1<#[a, Size] A: KnownSize +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsSST0<#[a, Size] A: Size +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsSST1<#[a, Size] A: KnownSize +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsSTS0<#[a, Size] A: Size +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsSTS1<#[a, Size] A: KnownSize +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsSTT0<#[a, Size] A: Size +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsSTT1<#[a, Size] A: KnownSize +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTSS0<#[a, Type] A: Type +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTSS1<#[a, Type] A: BoolOrIntType +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTSS2<#[a, Type] A: BundleType +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTSS3<#[a, Type] A: EnumType +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTSS4<#[a, Type] A: IntType +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTSS5<#[a, Type] A: StaticType +, #[b, Size] B: Size +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTST0<#[a, Type] A: Type +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTST1<#[a, Type] A: BoolOrIntType +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTST2<#[a, Type] A: BundleType +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTST3<#[a, Type] A: EnumType +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTST4<#[a, Type] A: IntType +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTST5<#[a, Type] A: StaticType +, #[b, Size] B: Size +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTS0<#[a, Type] A: Type +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTS1<#[a, Type] A: BoolOrIntType +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTS2<#[a, Type] A: BundleType +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTS3<#[a, Type] A: EnumType +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTS4<#[a, Type] A: IntType +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTS5<#[a, Type] A: StaticType +, #[b, Type] B: Type +, #[c, Size] C: Size +>);
+check_bounds!(CheckBoundsTTT0<#[a, Type] A: Type +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTT1<#[a, Type] A: BoolOrIntType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTT2<#[a, Type] A: BundleType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTT3<#[a, Type] A: EnumType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTT4<#[a, Type] A: IntType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+check_bounds!(CheckBoundsTTT5<#[a, Type] A: StaticType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
--- a/crates/fayalite/tests/module.rs
+++ b/crates/fayalite/tests/module.rs
--- a/crates/fayalite/tests/sim.rs
+++ b/crates/fayalite/tests/sim.rs
--- a/Show more
+++ b/Show more