crates/fayalite-proc-macros-impl/src/module/transform_body.rs

@@ -1109,7 +1109,7 @@ fn parse_quote_let_pat<T, R: ToTokens, C: Borrow<Token![:]>>(
     }
 }
 
-fn wrap_ty_with_expr(ty: impl ToTokens) -> Type {
+pub(crate) fn wrap_ty_with_expr(ty: impl ToTokens) -> Type {
     parse_quote_spanned! {ty.span()=>
         ::fayalite::expr::Expr<#ty>
     }
@@ -1586,7 +1586,7 @@ impl Visitor<'_> {
     }
 }
 
-fn empty_let() -> Local {
+pub(crate) fn empty_let() -> Local {
     Local {
         attrs: vec![],
         let_token: Default::default(),
@@ -1672,7 +1672,7 @@ impl Fold for Visitor<'_> {
         }
     }
 
-    fn fold_local(&mut self, let_stmt: Local) -> Local {
+    fn fold_local(&mut self, mut let_stmt: Local) -> Local {
         match self
             .errors
             .ok(HdlAttr::<Nothing, kw::hdl>::parse_and_leave_attr(
@@ -1682,6 +1682,25 @@ impl Fold for Visitor<'_> {
             Some(None) => return fold_local(self, let_stmt),
             Some(Some(HdlAttr { .. })) => {}
         };
+        let mut pat = &let_stmt.pat;
+        if let Pat::Type(pat_type) = pat {
+            pat = &pat_type.pat;
+        }
+        let Pat::Ident(syn::PatIdent {
+            attrs: _,
+            by_ref: None,
+            mutability: _,
+            ident: _,
+            subpat: None,
+        }) = pat
+        else {
+            let hdl_attr = HdlAttr::<Nothing, kw::hdl>::parse_and_take_attr(&mut let_stmt.attrs)
+                .ok()
+                .flatten()
+                .expect("already checked above");
+            let let_stmt = fold_local(self, let_stmt);
+            return self.process_hdl_let_pat(hdl_attr, let_stmt);
+        };
         let hdl_let = syn::parse2::<HdlLet<HdlLetKind<Type>>>(let_stmt.into_token_stream());
         let Some(hdl_let) = self.errors.ok(hdl_let) else {
             return empty_let();

crates/fayalite-proc-macros-impl/src/module/transform_body/expand_match.rs

@@ -3,22 +3,111 @@
 use crate::{
     fold::{impl_fold, DoFold},
     kw,
-    module::transform_body::{with_debug_clone_and_fold, Visitor},
+    module::transform_body::{empty_let, with_debug_clone_and_fold, wrap_ty_with_expr, Visitor},
     Errors, HdlAttr, PairsIterExt,
 };
 use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote_spanned, ToTokens, TokenStreamExt};
+use std::collections::BTreeSet;
 use syn::{
-    fold::{fold_arm, fold_expr_match, fold_pat, Fold},
+    fold::{fold_arm, fold_expr_match, fold_local, fold_pat, Fold},
     parse::Nothing,
     parse_quote_spanned,
     punctuated::Punctuated,
     spanned::Spanned,
     token::{Brace, Paren},
-    Arm, Attribute, Expr, ExprMatch, FieldPat, Ident, Member, Pat, PatIdent, PatOr, PatParen,
-    PatPath, PatRest, PatStruct, PatTupleStruct, PatWild, Path, PathSegment, Token, TypePath,
+    Arm, Attribute, Expr, ExprMatch, FieldPat, Ident, Local, Member, Pat, PatIdent, PatOr,
+    PatParen, PatPath, PatRest, PatStruct, PatTuple, PatTupleStruct, PatWild, Path, PathSegment,
+    Token, TypePath,
 };
 
+macro_rules! visit_trait {
+    (
+        $($vis:vis fn $fn:ident($state:ident: _, $value:ident: &$Value:ty) $block:block)*
+    ) => {
+        trait VisitMatchPat<'a> {
+            $(fn $fn(&mut self, $value: &'a $Value) {
+                $fn(self, $value);
+            })*
+        }
+
+        $($vis fn $fn<'a>($state: &mut (impl ?Sized + VisitMatchPat<'a>), $value: &'a $Value) $block)*
+    };
+}
+
+visit_trait! {
+    fn visit_match_pat_binding(_state: _, v: &MatchPatBinding) {
+        let MatchPatBinding { ident: _ } = v;
+    }
+    fn visit_match_pat_wild(_state: _, v: &MatchPatWild) {
+        let MatchPatWild { underscore_token: _ } = v;
+    }
+    fn visit_match_pat_rest(_state: _, v: &MatchPatRest) {
+        let MatchPatRest { dot2_token: _ } = v;
+    }
+    fn visit_match_pat_paren(state: _, v: &MatchPatParen<MatchPat>) {
+        let MatchPatParen { paren_token: _, pat } = v;
+        state.visit_match_pat(pat);
+    }
+    fn visit_match_pat_paren_simple(state: _, v: &MatchPatParen<MatchPatSimple>) {
+        let MatchPatParen { paren_token: _, pat } = v;
+        state.visit_match_pat_simple(pat);
+    }
+    fn visit_match_pat_or(state: _, v: &MatchPatOr<MatchPat>) {
+        let MatchPatOr { leading_vert: _, cases } = v;
+        for v in cases {
+            state.visit_match_pat(v);
+        }
+    }
+    fn visit_match_pat_or_simple(state: _, v: &MatchPatOr<MatchPatSimple>) {
+        let MatchPatOr { leading_vert: _, cases } = v;
+        for v in cases {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_struct_field(state: _, v: &MatchPatStructField) {
+        let MatchPatStructField { field_name: _, colon_token: _, pat } = v;
+        state.visit_match_pat_simple(pat);
+    }
+    fn visit_match_pat_struct(state: _, v: &MatchPatStruct) {
+        let MatchPatStruct { match_span: _, path: _, brace_token: _, fields, rest: _ } = v;
+        for v in fields {
+            state.visit_match_pat_struct_field(v);
+        }
+    }
+    fn visit_match_pat_tuple(state: _, v: &MatchPatTuple) {
+        let MatchPatTuple { paren_token: _, fields } = v;
+        for v in fields {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_enum_variant(state: _, v: &MatchPatEnumVariant) {
+        let MatchPatEnumVariant {match_span:_, variant_path: _, enum_path: _, variant_name: _, field } = v;
+        if let Some((_, v)) = field {
+            state.visit_match_pat_simple(v);
+        }
+    }
+    fn visit_match_pat_simple(state: _, v: &MatchPatSimple) {
+        match v {
+            MatchPatSimple::Paren(v) => state.visit_match_pat_paren_simple(v),
+            MatchPatSimple::Or(v) => state.visit_match_pat_or_simple(v),
+            MatchPatSimple::Binding(v) => state.visit_match_pat_binding(v),
+            MatchPatSimple::Wild(v) => state.visit_match_pat_wild(v),
+            MatchPatSimple::Rest(v) => state.visit_match_pat_rest(v),
+        }
+    }
+    fn visit_match_pat(state: _, v: &MatchPat) {
+        match v {
+            MatchPat::Simple(v) => state.visit_match_pat_simple(v),
+            MatchPat::Or(v) => state.visit_match_pat_or(v),
+            MatchPat::Paren(v) => state.visit_match_pat_paren(v),
+            MatchPat::Struct(v) => state.visit_match_pat_struct(v),
+            MatchPat::Tuple(v) => state.visit_match_pat_tuple(v),
+            MatchPat::EnumVariant(v) => state.visit_match_pat_enum_variant(v),
+        }
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatBinding<> {
         ident: Ident,
@@ -53,6 +142,15 @@ with_debug_clone_and_fold! {
     }
 }
 
+impl<P> MatchPatOr<P> {
+    /// returns the first `|` between two patterns
+    fn first_inner_vert(&self) -> Option<Token![|]> {
+        let mut pairs = self.cases.pairs();
+        pairs.next_back();
+        pairs.next().and_then(|v| v.into_tuple().1.copied())
+    }
+}
+
 impl<P: ToTokens> ToTokens for MatchPatOr<P> {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         let Self {
@@ -77,6 +175,19 @@ impl ToTokens for MatchPatWild {
     }
 }
 
+with_debug_clone_and_fold! {
+    struct MatchPatRest<> {
+        dot2_token: Token![..],
+    }
+}
+
+impl ToTokens for MatchPatRest {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self { dot2_token } = self;
+        dot2_token.to_tokens(tokens);
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatStructField<> {
         field_name: Ident,
@@ -159,6 +270,25 @@ impl ToTokens for MatchPatStruct {
     }
 }
 
+with_debug_clone_and_fold! {
+    struct MatchPatTuple<> {
+        paren_token: Paren,
+        fields: Punctuated<MatchPatSimple, Token![,]>,
+    }
+}
+
+impl ToTokens for MatchPatTuple {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            paren_token,
+            fields,
+        } = self;
+        paren_token.surround(tokens, |tokens| {
+            fields.to_tokens(tokens);
+        })
+    }
+}
+
 with_debug_clone_and_fold! {
     struct MatchPatEnumVariant<> {
         match_span: Span,
@@ -194,6 +324,7 @@ enum MatchPatSimple {
     Or(MatchPatOr<MatchPatSimple>),
     Binding(MatchPatBinding),
     Wild(MatchPatWild),
+    Rest(MatchPatRest),
 }
 
 impl_fold! {
@@ -202,6 +333,7 @@ impl_fold! {
         Or(MatchPatOr<MatchPatSimple>),
         Binding(MatchPatBinding),
         Wild(MatchPatWild),
+        Rest(MatchPatRest),
     }
 }
 
@@ -212,6 +344,7 @@ impl ToTokens for MatchPatSimple {
             Self::Paren(v) => v.to_tokens(tokens),
             Self::Binding(v) => v.to_tokens(tokens),
             Self::Wild(v) => v.to_tokens(tokens),
+            Self::Rest(v) => v.to_tokens(tokens),
         }
     }
 }
@@ -278,6 +411,7 @@ trait ParseMatchPat: Sized {
     fn or(v: MatchPatOr<Self>) -> Self;
     fn paren(v: MatchPatParen<Self>) -> Self;
     fn struct_(state: &mut HdlMatchParseState<'_>, v: MatchPatStruct) -> Result<Self, ()>;
+    fn tuple(state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()>;
     fn enum_variant(state: &mut HdlMatchParseState<'_>, v: MatchPatEnumVariant)
         -> Result<Self, ()>;
     fn parse(state: &mut HdlMatchParseState<'_>, pat: Pat) -> Result<Self, ()> {
@@ -462,7 +596,34 @@ trait ParseMatchPat: Sized {
             }) => Ok(Self::simple(MatchPatSimple::Wild(MatchPatWild {
                 underscore_token,
             }))),
-            Pat::Tuple(_) | Pat::Slice(_) | Pat::Const(_) | Pat::Lit(_) | Pat::Range(_) => {
+            Pat::Tuple(PatTuple {
+                attrs: _,
+                paren_token,
+                elems,
+            }) => {
+                let fields = elems
+                    .into_pairs()
+                    .filter_map_pair_value(|field_pat| {
+                        if let Pat::Rest(PatRest {
+                            attrs: _,
+                            dot2_token,
+                        }) = field_pat
+                        {
+                            Some(MatchPatSimple::Rest(MatchPatRest { dot2_token }))
+                        } else {
+                            MatchPatSimple::parse(state, field_pat).ok()
+                        }
+                    })
+                    .collect();
+                Self::tuple(
+                    state,
+                    MatchPatTuple {
+                        paren_token,
+                        fields,
+                    },
+                )
+            }
+            Pat::Slice(_) | Pat::Const(_) | Pat::Lit(_) | Pat::Range(_) => {
                 state
                     .errors
                     .error(pat, "not yet implemented in #[hdl] patterns");
@@ -497,6 +658,14 @@ impl ParseMatchPat for MatchPatSimple {
         Err(())
     }
 
+    fn tuple(state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()> {
+        state.errors.push(syn::Error::new(
+            v.paren_token.span.open(),
+            "matching tuples is not yet implemented inside structs/enums in #[hdl] patterns",
+        ));
+        Err(())
+    }
+
     fn enum_variant(
         state: &mut HdlMatchParseState<'_>,
         v: MatchPatEnumVariant,
@@ -515,6 +684,7 @@ enum MatchPat {
     Or(MatchPatOr<MatchPat>),
     Paren(MatchPatParen<MatchPat>),
     Struct(MatchPatStruct),
+    Tuple(MatchPatTuple),
     EnumVariant(MatchPatEnumVariant),
 }
 
@@ -524,6 +694,7 @@ impl_fold! {
         Or(MatchPatOr<MatchPat>),
         Paren(MatchPatParen<MatchPat>),
         Struct(MatchPatStruct),
+        Tuple(MatchPatTuple),
         EnumVariant(MatchPatEnumVariant),
     }
 }
@@ -545,6 +716,10 @@ impl ParseMatchPat for MatchPat {
         Ok(Self::Struct(v))
     }
 
+    fn tuple(_state: &mut HdlMatchParseState<'_>, v: MatchPatTuple) -> Result<Self, ()> {
+        Ok(Self::Tuple(v))
+    }
+
     fn enum_variant(
         _state: &mut HdlMatchParseState<'_>,
         v: MatchPatEnumVariant,
@@ -560,6 +735,7 @@ impl ToTokens for MatchPat {
             Self::Or(v) => v.to_tokens(tokens),
             Self::Paren(v) => v.to_tokens(tokens),
             Self::Struct(v) => v.to_tokens(tokens),
+            Self::Tuple(v) => v.to_tokens(tokens),
             Self::EnumVariant(v) => v.to_tokens(tokens),
         }
     }
@@ -622,10 +798,6 @@ struct RewriteAsCheckMatch {
 }
 
 impl Fold for RewriteAsCheckMatch {
-    fn fold_field_pat(&mut self, mut i: FieldPat) -> FieldPat {
-        i.colon_token = Some(Token![:](i.member.span()));
-        i
-    }
     fn fold_pat(&mut self, pat: Pat) -> Pat {
         match pat {
             Pat::Ident(mut pat_ident) => match parse_enum_ident(pat_ident.ident) {
@@ -740,6 +912,30 @@ impl Fold for RewriteAsCheckMatch {
         // don't recurse into expressions
         i
     }
+    fn fold_local(&mut self, mut let_stmt: Local) -> Local {
+        if let Some(syn::LocalInit {
+            eq_token,
+            expr: _,
+            diverge,
+        }) = let_stmt.init.take()
+        {
+            let_stmt.init = Some(syn::LocalInit {
+                eq_token,
+                expr: parse_quote_spanned! {self.span=>
+                    __match_value
+                },
+                diverge: diverge.map(|(else_, _expr)| {
+                    (
+                        else_,
+                        parse_quote_spanned! {self.span=>
+                            match __infallible {}
+                        },
+                    )
+                }),
+            });
+        }
+        fold_local(self, let_stmt)
+    }
 }
 
 struct HdlMatchParseState<'a> {
@@ -747,7 +943,123 @@ struct HdlMatchParseState<'a> {
     errors: &'a mut Errors,
 }
 
+struct HdlLetPatVisitState<'a> {
+    errors: &'a mut Errors,
+    bindings: BTreeSet<&'a Ident>,
+}
+
+impl<'a> VisitMatchPat<'a> for HdlLetPatVisitState<'a> {
+    fn visit_match_pat_binding(&mut self, v: &'a MatchPatBinding) {
+        self.bindings.insert(&v.ident);
+    }
+
+    fn visit_match_pat_or(&mut self, v: &'a MatchPatOr<MatchPat>) {
+        if let Some(first_inner_vert) = v.first_inner_vert() {
+            self.errors.error(
+                first_inner_vert,
+                "or-patterns are not supported in let statements",
+            );
+        }
+        visit_match_pat_or(self, v);
+    }
+
+    fn visit_match_pat_or_simple(&mut self, v: &'a MatchPatOr<MatchPatSimple>) {
+        if let Some(first_inner_vert) = v.first_inner_vert() {
+            self.errors.error(
+                first_inner_vert,
+                "or-patterns are not supported in let statements",
+            );
+        }
+        visit_match_pat_or_simple(self, v);
+    }
+
+    fn visit_match_pat_enum_variant(&mut self, v: &'a MatchPatEnumVariant) {
+        self.errors.error(v, "refutable pattern in let statement");
+    }
+}
+
 impl Visitor<'_> {
+    pub(crate) fn process_hdl_let_pat(
+        &mut self,
+        _hdl_attr: HdlAttr<Nothing, kw::hdl>,
+        mut let_stmt: Local,
+    ) -> Local {
+        let span = let_stmt.let_token.span();
+        if let Pat::Type(pat) = &mut let_stmt.pat {
+            *pat.ty = wrap_ty_with_expr((*pat.ty).clone());
+        }
+        let check_let_stmt = RewriteAsCheckMatch { span }.fold_local(let_stmt.clone());
+        let Local {
+            attrs: _,
+            let_token,
+            pat,
+            init,
+            semi_token,
+        } = let_stmt;
+        self.require_normal_module_or_fn(let_token);
+        let Some(syn::LocalInit {
+            eq_token,
+            expr,
+            diverge,
+        }) = init
+        else {
+            self.errors
+                .error(let_token, "#[hdl] let must be assigned a value");
+            return empty_let();
+        };
+        if let Some((else_, _)) = diverge {
+            // TODO: implement let-else
+            self.errors
+                .error(else_, "#[hdl] let ... else { ... } is not implemented");
+            return empty_let();
+        }
+        let Ok(pat) = MatchPat::parse(
+            &mut HdlMatchParseState {
+                match_span: span,
+                errors: &mut self.errors,
+            },
+            pat,
+        ) else {
+            return empty_let();
+        };
+        let mut state = HdlLetPatVisitState {
+            errors: &mut self.errors,
+            bindings: BTreeSet::new(),
+        };
+        state.visit_match_pat(&pat);
+        let HdlLetPatVisitState {
+            errors: _,
+            bindings,
+        } = state;
+        let retval = parse_quote_spanned! {span=>
+            let (#(#bindings,)* __scope,) = {
+                type __MatchTy<T> = <T as ::fayalite::ty::Type>::MatchVariant;
+                let __match_expr = ::fayalite::expr::ToExpr::to_expr(&(#expr));
+                ::fayalite::expr::check_match_expr(__match_expr, |__match_value, __infallible| {
+                    #[allow(unused_variables)]
+                    #check_let_stmt
+                    match __infallible {}
+                });
+                let mut __match_iter = ::fayalite::module::match_(__match_expr);
+                let ::fayalite::__std::option::Option::Some(__match_variant) = ::fayalite::__std::iter::Iterator::next(&mut __match_iter) else {
+                    ::fayalite::__std::unreachable!("#[hdl] let with uninhabited type");
+                };
+                let ::fayalite::__std::option::Option::None = ::fayalite::__std::iter::Iterator::next(&mut __match_iter) else {
+                    ::fayalite::__std::unreachable!("#[hdl] let with refutable pattern");
+                };
+                let (__match_variant, __scope) =
+                    ::fayalite::ty::MatchVariantAndInactiveScope::match_activate_scope(
+                        __match_variant,
+                    );
+                #let_token #pat #eq_token __match_variant #semi_token
+                (#(#bindings,)* __scope,)
+            };
+        };
+        match retval {
+            syn::Stmt::Local(retval) => retval,
+            _ => unreachable!(),
+        }
+    }
     pub(crate) fn process_hdl_match(
         &mut self,
         _hdl_attr: HdlAttr<Nothing, kw::hdl>,

crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs

@@ -2,6 +2,7 @@
 // See Notices.txt for copyright information
 //! ## `#[hdl] let` statements
 
+pub mod destructuring;
 pub mod inputs_outputs;
 pub mod instances;
 pub mod memories;

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);
+//!     }
+//! }
+//! ```

crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs

@@ -7,5 +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,
+//! `#[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(_))`.

crates/fayalite/src/int.rs

@@ -567,12 +567,12 @@ impl_prim_int!(i64, SInt<64>);
 impl_prim_int!(i128, SInt<128>);
 
 impl_prim_int!(
-    /// for portability reasons, [`usize`] always translates to [`UInt<64>`]
+    /// for portability reasons, [`usize`] always translates to [`UInt<64>`][type@UInt]
     usize, UInt<64>
 );
 
 impl_prim_int!(
-    /// for portability reasons, [`isize`] always translates to [`SInt<64>`]
+    /// for portability reasons, [`isize`] always translates to [`SInt<64>`][type@SInt]
     isize, SInt<64>
 );
 

crates/fayalite/tests/module.rs

@@ -4345,3 +4345,79 @@ circuit check_cfgs:
 ",
     };
 }
+
+#[hdl_module(outline_generated)]
+pub fn check_let_patterns() {
+    #[hdl]
+    let tuple_in: (UInt<1>, SInt<1>, Bool) = m.input();
+    #[hdl]
+    let (tuple_0, tuple_1, tuple_2) = tuple_in;
+    #[hdl]
+    let tuple_0_out: UInt<1> = m.output();
+    connect(tuple_0_out, tuple_0);
+    #[hdl]
+    let tuple_1_out: SInt<1> = m.output();
+    connect(tuple_1_out, tuple_1);
+    #[hdl]
+    let tuple_2_out: Bool = m.output();
+    connect(tuple_2_out, tuple_2);
+
+    #[hdl]
+    let test_struct_in: TestStruct<SInt<8>> = m.input();
+    #[hdl]
+    let TestStruct::<_> { a, b } = test_struct_in;
+    #[hdl]
+    let test_struct_a_out: SInt<8> = m.output();
+    connect(test_struct_a_out, a);
+    #[hdl]
+    let test_struct_b_out: UInt<8> = m.output();
+    connect(test_struct_b_out, b);
+
+    #[hdl]
+    let test_struct_2_in: TestStruct2 = m.input();
+    #[hdl]
+    let TestStruct2 { v } = test_struct_2_in;
+    #[hdl]
+    let test_struct_2_v_out: UInt<8> = m.output();
+    connect(test_struct_2_v_out, v);
+
+    #[hdl]
+    let test_struct_3_in: TestStruct3 = m.input();
+    #[hdl]
+    let TestStruct3 {} = test_struct_3_in;
+}
+
+#[test]
+fn test_let_patterns() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_let_patterns();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_let_patterns.fir": r"FIRRTL version 3.2.0
+circuit check_let_patterns:
+    type Ty0 = {`0`: UInt<1>, `1`: SInt<1>, `2`: UInt<1>}
+    type Ty1 = {a: SInt<8>, b: UInt<8>}
+    type Ty2 = {v: UInt<8>}
+    type Ty3 = {}
+    module check_let_patterns: @[module-XXXXXXXXXX.rs 1:1]
+        input tuple_in: Ty0 @[module-XXXXXXXXXX.rs 2:1]
+        output tuple_0_out: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
+        output tuple_1_out: SInt<1> @[module-XXXXXXXXXX.rs 6:1]
+        output tuple_2_out: UInt<1> @[module-XXXXXXXXXX.rs 8:1]
+        input test_struct_in: Ty1 @[module-XXXXXXXXXX.rs 10:1]
+        output test_struct_a_out: SInt<8> @[module-XXXXXXXXXX.rs 12:1]
+        output test_struct_b_out: UInt<8> @[module-XXXXXXXXXX.rs 14:1]
+        input test_struct_2_in: Ty2 @[module-XXXXXXXXXX.rs 16:1]
+        output test_struct_2_v_out: UInt<8> @[module-XXXXXXXXXX.rs 18:1]
+        input test_struct_3_in: Ty3 @[module-XXXXXXXXXX.rs 20:1]
+        connect tuple_0_out, tuple_in.`0` @[module-XXXXXXXXXX.rs 5:1]
+        connect tuple_1_out, tuple_in.`1` @[module-XXXXXXXXXX.rs 7:1]
+        connect tuple_2_out, tuple_in.`2` @[module-XXXXXXXXXX.rs 9:1]
+        connect test_struct_a_out, test_struct_in.a @[module-XXXXXXXXXX.rs 13:1]
+        connect test_struct_b_out, test_struct_in.b @[module-XXXXXXXXXX.rs 15:1]
+        connect test_struct_2_v_out, test_struct_2_in.v @[module-XXXXXXXXXX.rs 19:1]
+",
+    };
+}