fayalite::build::verilog: tell firtool to only preserve values with significant names

Add support to the simulator for running hdl asserts/assumes and being
able to write to the formal global clock/reset and all any/all_const/seq that are used.
This allows you to use the exact same HDL code for running a simulation and for running a formal proof.

crates/fayalite-proc-macros-impl/src/hdl_bundle.rs

@@ -1133,6 +1133,7 @@ impl ToTokens for ParsedBundle {
             let mut fields_expr_ne = vec![];
             let mut fields_valueless_eq = vec![];
             let mut fields_valueless_ne = vec![];
+            let mut fields_structural_eq = vec![];
             for field in fields.named() {
                 let field_ident = field.ident();
                 let field_ty = field.ty();
@@ -1141,6 +1142,9 @@ impl ToTokens for ParsedBundle {
                     .push(parse_quote_spanned! {cmp_eq.span=>
                         #field_ty: ::fayalite::expr::HdlPartialEqImpl<#field_ty>
                     });
+                fields_structural_eq.push(quote_spanned! {cmp_eq.span=>
+                    <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                });
                 fields_value_eq.push(quote_spanned! {span=>
                     ::fayalite::expr::HdlPartialEqImpl::cmp_value_eq(
                         __lhs.#field_ident,
@@ -1188,6 +1192,7 @@ impl ToTokens for ParsedBundle {
             let expr_ne_body;
             let valueless_eq_body;
             let valueless_ne_body;
+            let structural_eq;
             if fields_len == 0 {
                 value_eq_body = quote_spanned! {span=>
                     true
@@ -1207,6 +1212,9 @@ impl ToTokens for ParsedBundle {
                 valueless_ne_body = quote_spanned! {span=>
                     ::fayalite::expr::Valueless::new(::fayalite::int::Bool)
                 };
+                structural_eq = quote_spanned! {span=>
+                    true
+                };
             } else {
                 value_eq_body = quote_spanned! {span=>
                     #(#fields_value_eq)&*
@@ -1230,12 +1238,17 @@ impl ToTokens for ParsedBundle {
                     let __rhs = ::fayalite::expr::ValueType::ty(&__rhs);
                     #(#fields_valueless_ne)|*
                 };
+                structural_eq = quote_spanned! {span=>
+                    #(#fields_structural_eq)&&*
+                };
             };
             quote_spanned! {span=>
                 #[automatically_derived]
                 impl #impl_generics ::fayalite::expr::HdlPartialEqImpl<Self> for #target #type_generics
                 #cmp_eq_where_clause
                 {
+                    const TRY_STRUCTURAL_EQ: ::fayalite::__std::primitive::bool = #structural_eq;
+
                     #[track_caller]
                     fn cmp_value_eq(
                         __lhs: Self,
@@ -1261,6 +1274,16 @@ impl ToTokens for ParsedBundle {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            if let ::fayalite::__std::result::Result::Ok(__retval) =
+                                ::fayalite::expr::ops::StructuralEq::try_new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                )
+                            {
+                                return ::fayalite::expr::ToExpr::to_expr(&__retval);
+                            }
+                        }
                         #expr_eq_body
                     }
 
@@ -1269,6 +1292,14 @@ impl ToTokens for ParsedBundle {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            return !::fayalite::expr::ToExpr::to_expr(
+                                &::fayalite::expr::ops::StructuralEq::new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                ),
+                            );
+                        }
                         #expr_ne_body
                     }
 

crates/fayalite-proc-macros-impl/src/hdl_enum.rs

@@ -643,7 +643,9 @@ impl ToTokens for ParsedEnum {
                     #where_clause
                     {
                         #[allow(non_snake_case, dead_code)]
-                        #vis fn #ident(#self_token) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
+                        #vis fn #ident(
+                            #self_token,
+                        ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
                             ::fayalite::sim::value::SimValue::from_value(
                                 #self_token.#sim_builder_ty_field_ident,
                                 #sim_value_ident::#ident(::fayalite::enum_::EnumPaddingSimValue::new()),
@@ -929,8 +931,14 @@ impl ToTokens for ParsedEnum {
                 impl #impl_generics ::fayalite::__std::fmt::Display for #sim_value_ident #type_generics
                 #where_clause
                 {
-                    fn fmt(&self, f: &mut ::fayalite::__std::fmt::Formatter<'_>) -> ::fayalite::__std::fmt::Result {
+                    fn fmt(
-                        <#target #type_generics as ::fayalite::ty::SimValueDisplay>::sim_value_display(self, f)
+                        &self,
+                        f: &mut ::fayalite::__std::fmt::Formatter<'_>,
+                    ) -> ::fayalite::__std::fmt::Result {
+                        <#target #type_generics as ::fayalite::ty::SimValueDisplay>::sim_value_display(
+                            self,
+                            f,
+                        )
                     }
                 }
             }.to_tokens(tokens);
@@ -946,6 +954,7 @@ impl ToTokens for ParsedEnum {
             let mut variants_value_eq = vec![];
             let mut variants_expr_eq = vec![];
             let mut fields_valueless_eq = vec![];
+            let mut structural_eq: Option<TokenStream> = None;
             for (
                 variant_index,
                 ParsedVariant {
@@ -971,8 +980,23 @@ impl ToTokens for ParsedEnum {
                         .push(parse_quote_spanned! {cmp_eq.span=>
                             #field_ty: ::fayalite::expr::HdlPartialEqImpl<#field_ty>
                         });
+                    match &mut structural_eq {
+                        Some(structural_eq) => {
+                            structural_eq.extend(quote_spanned! {cmp_eq.span=>
+                                && <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                            });
+                        }
+                        None => {
+                            structural_eq = Some(quote_spanned! {cmp_eq.span=>
+                                <#field_ty as ::fayalite::expr::HdlPartialEqImpl<#field_ty>>::TRY_STRUCTURAL_EQ
+                            });
+                        }
+                    }
                     variants_value_eq.push(quote_spanned! {span=>
-                        (#sim_value_ident::#variant_ident(__lhs_field, _), #sim_value_ident::#variant_ident(__rhs_field, _)) => {
+                        (
+                            #sim_value_ident::#variant_ident(__lhs_field, _),
+                            #sim_value_ident::#variant_ident(__rhs_field, _),
+                        ) => {
                             ::fayalite::expr::HdlPartialEqImpl::cmp_value_eq(
                                 __lhs.#variant_ident,
                                 ::fayalite::__std::borrow::Cow::Borrowed(__lhs_field),
@@ -1002,7 +1026,10 @@ impl ToTokens for ParsedEnum {
                             else {
                                 ::fayalite::__std::unreachable!();
                             };
-                            ::fayalite::module::connect(__retval, ::fayalite::expr::HdlPartialEqImpl::cmp_expr_eq(__lhs, __rhs));
+                            ::fayalite::module::connect(
+                                __retval,
+                                ::fayalite::expr::HdlPartialEqImpl::cmp_expr_eq(__lhs, __rhs),
+                            );
                         }
                     });
                     fields_valueless_eq.push(quote_spanned! {span=>
@@ -1043,7 +1070,10 @@ impl ToTokens for ParsedEnum {
             }
             if let Some(sim_value_unknown_variant_name) = &sim_value_unknown_variant_name {
                 variants_value_eq.push(quote_spanned! {span=>
-                    (#sim_value_ident::#sim_value_unknown_variant_name(__lhs_unknown), #sim_value_ident::#sim_value_unknown_variant_name(__rhs_unknown)) => {
+                    (
+                        #sim_value_ident::#sim_value_unknown_variant_name(__lhs_unknown),
+                        #sim_value_ident::#sim_value_unknown_variant_name(__rhs_unknown),
+                    ) => {
                         __lhs_unknown == __rhs_unknown
                     }
                 });
@@ -1060,17 +1090,26 @@ impl ToTokens for ParsedEnum {
                 }
             };
             let cmp_expr_eq_wire_name = format!("{ident}_cmp_eq");
+            let structural_eq = structural_eq.unwrap_or_else(|| {
+                quote_spanned! {span=>
+                    true
+                }
+            });
             quote_spanned! {span=>
                 #[automatically_derived]
                 impl #impl_generics ::fayalite::expr::HdlPartialEqImpl<Self> for #target #type_generics
                 #cmp_eq_where_clause
                 {
+                    const TRY_STRUCTURAL_EQ: ::fayalite::__std::primitive::bool = #structural_eq;
+
                     #[track_caller]
                     fn cmp_value_eq(
                         __lhs: Self,
-                        __lhs_value: ::fayalite::__std::borrow::Cow<'_, <Self as ::fayalite::ty::Type>::SimValue>,
+                        __lhs_value: ::fayalite::__std::borrow::Cow<'_,
+                            <Self as ::fayalite::ty::Type>::SimValue>,
                         __rhs: Self,
-                        __rhs_value: ::fayalite::__std::borrow::Cow<'_, <Self as ::fayalite::ty::Type>::SimValue>,
+                        __rhs_value: ::fayalite::__std::borrow::Cow<'_,
+                            <Self as ::fayalite::ty::Type>::SimValue>,
                     ) -> ::fayalite::__std::primitive::bool {
                         match (&*__lhs_value, &*__rhs_value) {
                             #(#variants_value_eq)*
@@ -1083,7 +1122,20 @@ impl ToTokens for ParsedEnum {
                         __lhs: ::fayalite::expr::Expr<Self>,
                         __rhs: ::fayalite::expr::Expr<Self>,
                     ) -> ::fayalite::expr::Expr<::fayalite::int::Bool> {
-                        let __retval = ::fayalite::module::wire(::fayalite::module::ImplicitName(#cmp_expr_eq_wire_name), ::fayalite::int::Bool);
+                        if <Self as ::fayalite::expr::HdlPartialEqImpl<Self>>::TRY_STRUCTURAL_EQ {
+                            if let ::fayalite::__std::result::Result::Ok(__retval) =
+                                ::fayalite::expr::ops::StructuralEq::try_new(
+                                    ::fayalite::expr::Expr::canonical(__lhs),
+                                    ::fayalite::expr::Expr::canonical(__rhs),
+                                )
+                            {
+                                return ::fayalite::expr::ToExpr::to_expr(&__retval);
+                            }
+                        }
+                        let __retval = ::fayalite::module::wire(
+                            ::fayalite::module::ImplicitName(#cmp_expr_eq_wire_name),
+                            ::fayalite::int::Bool,
+                        );
                         ::fayalite::module::connect(__retval, false);
                         let mut __lhs_match_variant_iter = ::fayalite::module::match_(__lhs);
                         #(#variants_expr_eq)*
@@ -1112,7 +1164,8 @@ impl ToTokens for ParsedEnum {
                 type SimValue = #sim_value_ident #type_generics;
                 type MatchVariant = #match_variant_ident #type_generics;
                 type MatchActiveScope = ::fayalite::module::Scope;
-                type MatchVariantAndInactiveScope = ::fayalite::enum_::EnumMatchVariantAndInactiveScope<Self>;
+                type MatchVariantAndInactiveScope =
+                    ::fayalite::enum_::EnumMatchVariantAndInactiveScope<Self>;
                 type MatchVariantsIter = ::fayalite::enum_::EnumMatchVariantsIter<Self>;
 
                 fn match_variants(
@@ -1125,7 +1178,9 @@ impl ToTokens for ParsedEnum {
                     ::fayalite::int::Bool
                 }
                 fn canonical(&#self_token) -> ::fayalite::ty::CanonicalType {
-                    ::fayalite::ty::CanonicalType::Enum(::fayalite::enum_::Enum::new(::fayalite::enum_::EnumType::variants(#self_token)))
+                    ::fayalite::ty::CanonicalType::Enum(::fayalite::enum_::Enum::new(
+                        ::fayalite::enum_::EnumType::variants(#self_token),
+                    ))
                 }
                 #[track_caller]
                 #[allow(non_snake_case)]
@@ -1134,7 +1189,11 @@ impl ToTokens for ParsedEnum {
                         ::fayalite::__std::panic!("expected enum");
                     };
                     let #variants_token = ::fayalite::enum_::EnumType::variants(&enum_);
-                    ::fayalite::__std::assert_eq!(#variants_token.len(), #variants_len, "enum has wrong number of variants");
+                    ::fayalite::__std::assert_eq!(
+                        #variants_token.len(),
+                        #variants_len,
+                        "enum has wrong number of variants",
+                    );
                     Self {
                         #(#from_canonical_body_fields)*
                     }
@@ -1180,7 +1239,10 @@ impl ToTokens for ParsedEnum {
                 type SimBuilder = #sim_builder_ident #type_generics;
                 fn match_activate_scope(
                     v: <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
-                ) -> (<Self as ::fayalite::ty::Type>::MatchVariant, <Self as ::fayalite::ty::Type>::MatchActiveScope) {
+                ) -> (
+                    <Self as ::fayalite::ty::Type>::MatchVariant,
+                    <Self as ::fayalite::ty::Type>::MatchActiveScope,
+                ) {
                     let (#variant_access_token, scope) = v.activate();
                     (
                         match #variant_access_token.variant_index() {
@@ -1200,7 +1262,10 @@ impl ToTokens for ParsedEnum {
             impl #impl_generics ::fayalite::__std::fmt::Debug for #sim_value_ident #type_generics
             #where_clause
             {
-                fn fmt(&self, f: &mut ::fayalite::__std::fmt::Formatter<'_>) -> ::fayalite::__std::fmt::Result {
+                fn fmt(
+                    &self,
+                    f: &mut ::fayalite::__std::fmt::Formatter<'_>,
+                ) -> ::fayalite::__std::fmt::Result {
                     <#target #type_generics as ::fayalite::ty::SimValueDebug>::sim_value_debug(self, f)
                 }
             }
@@ -1213,7 +1278,10 @@ impl ToTokens for ParsedEnum {
                     &self,
                     ty: #target #type_generics,
                 ) -> ::fayalite::sim::value::SimValue<#target #type_generics> {
-                    ::fayalite::sim::value::SimValue::from_value(ty, ::fayalite::__std::clone::Clone::clone(self))
+                    ::fayalite::sim::value::SimValue::from_value(
+                        ty,
+                        ::fayalite::__std::clone::Clone::clone(self),
+                    )
                 }
                 fn into_sim_value_with_type(
                     self,

crates/fayalite/src/annotations.rs

@@ -238,7 +238,10 @@ impl TargetedAnnotation {
     }
     #[track_caller]
     pub fn assert_valid_target(target: Interned<Target>) {
-        assert!(target.is_static(), "can't annotate non-static targets");
+        assert!(
+            target.is_valid_annotation_target(),
+            "not a valid annotation target: {target:?}",
+        );
     }
     pub fn target(&self) -> Interned<Target> {
         self.target

crates/fayalite/src/array.rs

@@ -4,7 +4,7 @@
 use crate::{
     expr::{
         CastToBits, Expr, HdlPartialEq, HdlPartialEqImpl, ReduceBits, ToExpr, ValueType, Valueless,
-        ops::{ArrayLiteral, ExprFromIterator, ExprIntoIterator},
+        ops::{ArrayLiteral, ExprFromIterator, ExprIntoIterator, StructuralEq},
     },
     int::{Bool, DYN_SIZE, DynSize, KnownSize, Size, SizeType},
     intern::{Intern, Interned, LazyInterned},
@@ -367,6 +367,8 @@ impl<Lhs: Type, Rhs: Type, Len: Size> HdlPartialEqImpl<ArrayType<Rhs, Len>> for
 where
     Lhs: HdlPartialEqImpl<Rhs>,
 {
+    const TRY_STRUCTURAL_EQ: bool = <Lhs as HdlPartialEqImpl<Rhs>>::TRY_STRUCTURAL_EQ;
+
     fn cmp_value_eq(
         lhs: Self,
         lhs_value: Cow<'_, Self::SimValue>,
@@ -387,6 +389,11 @@ where
     }
     fn cmp_expr_eq(lhs: Expr<Self>, rhs: Expr<ArrayType<Rhs, Len>>) -> Expr<Bool> {
         assert_eq!(lhs.ty().len(), rhs.ty().len());
+        if Self::TRY_STRUCTURAL_EQ {
+            if let Ok(retval) = StructuralEq::try_new(Expr::canonical(lhs), Expr::canonical(rhs)) {
+                return retval.to_expr();
+            }
+        }
         lhs.into_iter()
             .zip(rhs)
             .map(|(l, r)| l.cmp_eq(r))
@@ -396,6 +403,11 @@ where
     }
     fn cmp_expr_ne(lhs: Expr<Self>, rhs: Expr<ArrayType<Rhs, Len>>) -> Expr<Bool> {
         assert_eq!(lhs.ty().len(), rhs.ty().len());
+        if Self::TRY_STRUCTURAL_EQ {
+            if let Ok(retval) = StructuralEq::try_new(Expr::canonical(lhs), Expr::canonical(rhs)) {
+                return !retval.to_expr();
+            }
+        }
         lhs.into_iter()
             .zip(rhs)
             .map(|(l, r)| l.cmp_ne(r))

crates/fayalite/src/build/graph.rs

@@ -12,7 +12,7 @@ use crate::{
 use eyre::{ContextCompat, eyre};
 use petgraph::{
     algo::{DfsSpace, kosaraju_scc, toposort},
-    graph::DiGraph,
+    graph::{DiGraph, NodeIndex},
     visit::{GraphBase, Visitable},
 };
 use serde::{Deserialize, Deserializer, Serialize, Serializer, de::Error, ser::SerializeSeq};
@@ -465,7 +465,7 @@ impl JobGraph {
                         }
                     })
                     .expect("we know there's a cycle");
-                let cycle_set = HashSet::from_iter(cycle.iter().copied());
+                let cycle_set = HashSet::<NodeIndex>::from_iter(cycle.iter().copied());
                 let job = cycle
                     .into_iter()
                     .find_map(|node_id| {
@@ -701,7 +701,7 @@ impl JobGraph {
                 job: DynJob,
                 thread: ScopedJoinHandle<'scope, eyre::Result<Vec<JobItem>>>,
             }
-            let mut running_jobs = HashMap::default();
+            let mut running_jobs = HashMap::<NodeIndex, RunningJob>::default();
             let (finished_jobs_sender, finished_jobs_receiver) = mpsc::channel();
             let mut next_finished_job = None;
             loop {

crates/fayalite/src/build/verilog.rs

@@ -211,7 +211,7 @@ impl ExternalCommand for UnadjustedVerilog {
         args.write_arg("-o");
         args.write_interned_arg(unadjusted_verilog_file_name);
         if verilog_debug {
-            args.write_args(["-g", "--preserve-values=all"]);
+            args.write_args(["-g", "--preserve-values=named"]);
         }
         if let Some(dialect) = verilog_dialect {
             args.write_args(dialect.firtool_extra_args().iter().copied());

crates/fayalite/src/bundle.rs

@@ -5,7 +5,7 @@ use crate::{
     expr::{
         CastToBits, Expr, HdlPartialEqImpl, ReduceBits, ToExpr, ToSimValueInner, ValueType,
         Valueless,
-        ops::{ArrayLiteral, BundleLiteral},
+        ops::{ArrayLiteral, BundleLiteral, StructuralEq},
         value_category::{ValueCategoryCommon, ValueCategoryExpr, ValueCategoryValue},
     },
     int::{Bool, DynSize},
@@ -708,6 +708,8 @@ macro_rules! impl_tuples {
             }
         }
         impl<$($Lhs: Type + HdlPartialEqImpl<$Rhs>, $Rhs: Type,)*> HdlPartialEqImpl<($($Rhs,)*)> for ($($Lhs,)*) {
+            const TRY_STRUCTURAL_EQ: bool = true $(&& <$Lhs as HdlPartialEqImpl<$Rhs>>::TRY_STRUCTURAL_EQ)*;
+
             #[track_caller]
             fn cmp_value_eq(
                 lhs: Self,
@@ -725,6 +727,11 @@ macro_rules! impl_tuples {
 
             #[track_caller]
             fn cmp_expr_eq(lhs: Expr<Self>, rhs: Expr<($($Rhs,)*)>) -> Expr<Bool> {
+                if Self::TRY_STRUCTURAL_EQ {
+                    if let Ok(retval) = StructuralEq::try_new(Expr::canonical(lhs), Expr::canonical(rhs)) {
+                        return retval.to_expr();
+                    }
+                }
                 let ($($lhs_var,)*) = *lhs;
                 let ($($rhs_var,)*) = *rhs;
                 ArrayLiteral::<Bool, DynSize>::new(
@@ -737,6 +744,11 @@ macro_rules! impl_tuples {
 
             #[track_caller]
             fn cmp_expr_ne(lhs: Expr<Self>, rhs: Expr<($($Rhs,)*)>) -> Expr<Bool> {
+                if Self::TRY_STRUCTURAL_EQ {
+                    if let Ok(retval) = StructuralEq::try_new(Expr::canonical(lhs), Expr::canonical(rhs)) {
+                        return !retval.to_expr();
+                    }
+                }
                 let ($($lhs_var,)*) = *lhs;
                 let ($($rhs_var,)*) = *rhs;
                 ArrayLiteral::<Bool, DynSize>::new(

crates/fayalite/src/expr.rs

@@ -6,6 +6,7 @@ use crate::{
     bundle::{Bundle, BundleType},
     enum_::{Enum, EnumType},
     expr::target::{GetTarget, Target},
+    formal::FormalInput,
     int::{Bool, DynSize, IntType, SIntValue, Size, SizeType, UInt, UIntType, UIntValue},
     intern::{Intern, Interned},
     memory::{DynPortType, MemPort, PortType},
@@ -220,6 +221,7 @@ expr_enum! {
         CastBitsTo(ops::CastBitsTo),
         ToTraceAsString(ops::ToTraceAsString),
         TraceAsStringAsInner(ops::TraceAsStringAsInner),
+        StructuralEq(ops::StructuralEq),
         ModuleIO(ModuleIO<CanonicalType>),
         Instance(Instance<Bundle>),
         Wire(Wire<CanonicalType>),
@@ -227,6 +229,8 @@ expr_enum! {
         RegSync(Reg<CanonicalType, SyncReset>),
         RegAsync(Reg<CanonicalType, AsyncReset>),
         MemPort(MemPort<DynPortType>),
+        FormalInput(FormalInput),
+        SimIoForGlobal(ops::SimIoForGlobal),
     }
 }
 
@@ -698,6 +702,7 @@ macro_rules! impl_hdl_cmp {
             impl_helper = $HdlCmpImplHelper:ident,
             $(impl_helper_base = $HdlCmpImplHelperBase:ident,)?
             impl_helper_sealed = $HdlCmpImplHelperSealed:ident,
+            $(try_structural_eq = $TRY_STRUCTURAL_EQ:ident,)?
         ]
         $vis:vis trait $HdlCmp:ident<$Rhs:ident: ValueType>:
             ValueType<Type: $HdlCmpImpl:ident<Rhs::Type> $(+ $HdlCmpImplBase:ident<Rhs::Type>)?> $(+ $HdlCmpBase:ident<Rhs>)?
@@ -726,6 +731,8 @@ macro_rules! impl_hdl_cmp {
         }
 
         $vis trait $HdlCmpImpl<$Rhs: Type>: Type $(+ $HdlCmpImplBase<$Rhs>)? {
+            $(const $TRY_STRUCTURAL_EQ: bool;)?
+
             $(#[track_caller]
             fn $cmp_value_fn(
                 $cmp_value_lhs: Self,
@@ -909,6 +916,7 @@ impl_hdl_cmp! {
     #[
         impl_helper = HdlPartialEqImplHelper,
         impl_helper_sealed = HdlPartialEqImplHelperSealed,
+        try_structural_eq = TRY_STRUCTURAL_EQ,
     ]
     pub trait HdlPartialEq<Rhs: ValueType>:
         ValueType<Type: HdlPartialEqImpl<Rhs::Type> >
@@ -1908,3 +1916,19 @@ impl<T: ?Sized + ValueType> ToTraceAsStringImpl<T::Type, value_category::ValueCa
         Valueless::new(ty.with_new_inner_ty(this.ty().intern_sized()))
     }
 }
+
+impl ToLiteralBits for FormalInput {
+    fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
+        Err(NotALiteralExpr)
+    }
+}
+
+impl ToExpr for FormalInput {
+    fn to_expr(&self) -> Expr<Self::Type> {
+        Expr {
+            __enum: ExprEnum::FormalInput(*self).intern_sized(),
+            __ty: self.ty(),
+            __flow: self.flow(),
+        }
+    }
+}

crates/fayalite/src/expr/ops.rs

@@ -17,11 +17,12 @@ use crate::{
         },
         value_category::ValueCategoryExpr,
     },
+    formal::FormalInput,
     int::{
         Bool, BoolOrIntType, DynSize, IntType, KnownSize, SInt, SIntType, SIntValue, Size, UInt,
         UIntType, UIntValue,
     },
-    intern::{Intern, Interned},
+    intern::{Intern, Interned, MemoizeGeneric},
     phantom_const::{PhantomConst, PhantomConstValue},
     reset::{
         AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset, ToAsyncReset, ToReset,
@@ -2983,6 +2984,7 @@ macro_rules! impl_compare_op {
         #[to_dyn_type($lhs:ident => $dyn_lhs:expr, $rhs:ident => $dyn_rhs:expr)]
         #[to_cmp_value($lhs_compare_value:ident => $lhs_compare_value_expr:expr, $rhs_compare_value:ident => $rhs_compare_value_expr:expr)]
         #[type($Lhs:ty, $Rhs:ty)]
+        $(#[try_structural_eq = $TRY_STRUCTURAL_EQ:ident])?
         #[trait($Trait:ident)]
         $(
             struct $name:ident;
@@ -3044,6 +3046,7 @@ macro_rules! impl_compare_op {
         })*
 
         impl$(<$LhsWidth: Size, $RhsWidth: Size>)? $Trait<$Rhs> for $Lhs {
+            $(const $TRY_STRUCTURAL_EQ: bool = true;)?
             $(fn $value_method(
                 _lhs: Self,
                 $lhs_compare_value: Cow<'_, <Self as Type>::SimValue>,
@@ -3064,6 +3067,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => lhs, rhs => rhs)]
     #[to_cmp_value(lhs_value => &*lhs_value, rhs_value => &*rhs_value)]
     #[type(Bool, Bool)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqB; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeB; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3087,6 +3091,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(UIntType<LhsWidth>, UIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqU; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeU; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3111,6 +3116,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(SIntType<LhsWidth>, SIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqS; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeS; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3132,6 +3138,8 @@ impl_compare_op! {
 macro_rules! impl_compare_forwards_to_bool {
     ($ty:ident) => {
         impl HdlPartialEqImpl<Self> for $ty {
+            const TRY_STRUCTURAL_EQ: bool = true;
+
             #[track_caller]
             fn cmp_value_eq(
                 _lhs: Self,
@@ -4881,3 +4889,336 @@ impl<T: Type> ToExpr for TraceAsStringAsInner<T> {
         }
     }
 }
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+/// The [`Simulation::io()`] equivalent for a global signal, this is a flipped version of a global signal
+/// that allows you to e.g. use [`Simulation::write()`] to write to [`formal_global_clock()`].
+///
+/// [`Simulation::io()`]: crate::sim::Simulation::io
+/// [`Simulation::write()`]: crate::sim::Simulation::write
+/// [`formal_global_clock()`]: crate::formal::formal_global_clock
+pub struct SimIoForGlobal {
+    global: FormalInput,
+}
+
+impl fmt::Debug for SimIoForGlobal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("SimIoForGlobal").field(&self.global).finish()
+    }
+}
+
+impl SimIoForGlobal {
+    pub fn new(global: FormalInput) -> Self {
+        Self { global }
+    }
+    pub fn global(self) -> FormalInput {
+        self.global
+    }
+    pub(crate) fn must_connect_to(self) -> bool {
+        true
+    }
+    pub fn flow(self) -> Flow {
+        self.global.flow().flip()
+    }
+    pub(crate) fn source_location(self) -> crate::source_location::SourceLocation {
+        self.global.source_location()
+    }
+}
+
+impl GetTarget for SimIoForGlobal {
+    fn target(&self) -> Option<Interned<Target>> {
+        Some(Target::from(*self).intern_sized())
+    }
+}
+
+impl ToLiteralBits for SimIoForGlobal {
+    fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
+        Err(NotALiteralExpr)
+    }
+}
+
+impl ValueType for SimIoForGlobal {
+    type Type = CanonicalType;
+    type ValueCategory = ValueCategoryExpr;
+
+    fn ty(&self) -> Self::Type {
+        self.global.ty()
+    }
+}
+
+impl ToExpr for SimIoForGlobal {
+    fn to_expr(&self) -> Expr<Self::Type> {
+        Expr {
+            __enum: ExprEnum::SimIoForGlobal(*self).intern(),
+            __ty: self.ty(),
+            __flow: self.flow(),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub struct StructuralEqFlags {
+    pub assume_padding_is_zeroed: bool,
+}
+
+impl StructuralEqFlags {
+    pub const DEFAULT: Self = Self {
+        assume_padding_is_zeroed: false,
+    };
+}
+
+impl Default for StructuralEqFlags {
+    fn default() -> Self {
+        Self::DEFAULT
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[non_exhaustive]
+pub enum StructuralEqError {
+    TypesAreNotEqual {
+        lhs: CanonicalType,
+        rhs: CanonicalType,
+    },
+    TypeContainsSimOnly {
+        ty: CanonicalType,
+    },
+}
+
+impl fmt::Display for StructuralEqError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::TypesAreNotEqual { lhs, rhs } => write!(
+                f,
+                "StructuralEq lhs type must be the same as rhs type:\nlhs: {lhs:#?}\nrhs: {rhs:#?}\n",
+            ),
+            Self::TypeContainsSimOnly { ty } => write!(
+                f,
+                "StructuralEq input type must not contain SimOnly type: {ty:#?}",
+            ),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct StructuralEq {
+    lhs: Expr<CanonicalType>,
+    rhs: Expr<CanonicalType>,
+    flags: StructuralEqFlags,
+    literal_bits: Result<Interned<BitSlice>, NotALiteralExpr>,
+}
+
+impl StructuralEq {
+    fn literal_eq(
+        ty: CanonicalType,
+        l: Interned<BitSlice>,
+        r: Interned<BitSlice>,
+    ) -> Result<bool, NotALiteralExpr> {
+        enum PairRefOrInternedBitSlice<'a> {
+            Ref(&'a BitSlice, &'a BitSlice),
+            Interned(Interned<BitSlice>, Interned<BitSlice>),
+        }
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize(CanonicalType);
+        impl MemoizeGeneric for MyMemoize {
+            type InputRef<'a> = (&'a BitSlice, &'a BitSlice);
+            type InputOwned = (Interned<BitSlice>, Interned<BitSlice>);
+            type InputCow<'a> = PairRefOrInternedBitSlice<'a>;
+            type Output = Result<bool, NotALiteralExpr>;
+
+            fn input_eq(a: Self::InputRef<'_>, b: Self::InputRef<'_>) -> bool {
+                a == b
+            }
+
+            fn input_borrow(input: &Self::InputOwned) -> Self::InputRef<'_> {
+                let (l, r) = input;
+                (l, r)
+            }
+
+            fn input_cow_into_owned(input: Self::InputCow<'_>) -> Self::InputOwned {
+                match input {
+                    PairRefOrInternedBitSlice::Ref(l, r) => (l.intern(), r.intern()),
+                    PairRefOrInternedBitSlice::Interned(l, r) => (l, r),
+                }
+            }
+
+            fn input_cow_borrow<'a>(input: &'a Self::InputCow<'_>) -> Self::InputRef<'a> {
+                match input {
+                    PairRefOrInternedBitSlice::Ref(l, r) => (l, r),
+                    PairRefOrInternedBitSlice::Interned(l, r) => (l, r),
+                }
+            }
+
+            fn input_cow_from_owned<'a>(input: Self::InputOwned) -> Self::InputCow<'a> {
+                let (l, r) = input;
+                PairRefOrInternedBitSlice::Interned(l, r)
+            }
+
+            fn input_cow_from_ref(input: Self::InputRef<'_>) -> Self::InputCow<'_> {
+                let (l, r) = input;
+                PairRefOrInternedBitSlice::Ref(l, r)
+            }
+
+            fn inner(self, input: Self::InputRef<'_>) -> Self::Output {
+                let (mut l, mut r) = input;
+                match self.0 {
+                    CanonicalType::UInt(_)
+                    | CanonicalType::SInt(_)
+                    | CanonicalType::Bool(_)
+                    | CanonicalType::AsyncReset(_)
+                    | CanonicalType::SyncReset(_)
+                    | CanonicalType::Reset(_)
+                    | CanonicalType::Clock(_)
+                    | CanonicalType::PhantomConst(_) => Ok(l == r),
+                    CanonicalType::Array(ty) => {
+                        let element_ty = ty.element();
+                        let element_bit_width = element_ty.bit_width();
+                        let mut eq = true;
+                        for element_index in 0..ty.len() {
+                            if !Self(element_ty).get((
+                                &l[element_bit_width * element_index..][..element_bit_width],
+                                &r[element_bit_width * element_index..][..element_bit_width],
+                            ))? {
+                                eq = false;
+                                break;
+                            }
+                        }
+                        Ok(eq)
+                    }
+                    CanonicalType::Enum(ty) => {
+                        let discriminant_bit_width = ty.discriminant_bit_width();
+                        let (l_discriminant_bits, l_body_bits) = l.split_at(discriminant_bit_width);
+                        let (r_discriminant_bits, r_body_bits) = r.split_at(discriminant_bit_width);
+                        if l_discriminant_bits != r_discriminant_bits {
+                            return Ok(false);
+                        }
+                        let mut discriminant = 0usize;
+                        discriminant.view_bits_mut::<Lsb0>()[..l_discriminant_bits.len()]
+                            .copy_from_bitslice(l_discriminant_bits);
+                        match ty.variants().get(discriminant) {
+                            Some(&EnumVariant {
+                                name: _,
+                                ty: Some(variant_ty),
+                            }) => {
+                                let variant_bit_width = variant_ty.bit_width();
+                                Self(variant_ty).get((
+                                    &l_body_bits[..variant_bit_width],
+                                    &r_body_bits[..variant_bit_width],
+                                ))
+                            }
+                            Some(EnumVariant { name: _, ty: None }) => Ok(true),
+                            None => Err(NotALiteralExpr),
+                        }
+                    }
+                    CanonicalType::Bundle(ty) => {
+                        let mut eq = true;
+                        for field in &ty.fields() {
+                            let field_bit_width = field.ty.bit_width();
+                            let l_field;
+                            let r_field;
+                            (l_field, l) = l.split_at(field_bit_width);
+                            (r_field, r) = r.split_at(field_bit_width);
+                            if !Self(field.ty).get((l_field, r_field))? {
+                                eq = false;
+                                break;
+                            }
+                        }
+                        Ok(eq)
+                    }
+                    CanonicalType::DynSimOnly(_) => unreachable!("doesn't have literal_bits"),
+                    CanonicalType::TraceAsString(ty) => Self(ty.inner_ty()).get((l, r)),
+                }
+            }
+        }
+        MyMemoize(ty).get_owned((l, r))
+    }
+    #[track_caller]
+    pub fn new(lhs: Expr<CanonicalType>, rhs: Expr<CanonicalType>) -> Self {
+        Self::with_flags(lhs, rhs, StructuralEqFlags::DEFAULT)
+    }
+    #[track_caller]
+    pub fn with_flags(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Self {
+        match Self::try_with_flags(lhs, rhs, flags) {
+            Ok(retval) => retval,
+            Err(e) => panic!("{e}"),
+        }
+    }
+    pub fn try_new(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+    ) -> Result<Self, StructuralEqError> {
+        Self::try_with_flags(lhs, rhs, StructuralEqFlags::DEFAULT)
+    }
+    pub fn try_with_flags(
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Self, StructuralEqError> {
+        let ty = lhs.ty();
+        let rhs_ty = rhs.ty();
+        if ty != rhs_ty {
+            return Err(StructuralEqError::TypesAreNotEqual {
+                lhs: ty,
+                rhs: rhs_ty,
+            });
+        }
+        if ty.contains_sim_only() {
+            return Err(StructuralEqError::TypeContainsSimOnly { ty });
+        }
+        Ok(Self {
+            lhs,
+            rhs,
+            flags,
+            literal_bits: lhs.to_literal_bits().and_then(|lhs| {
+                let rhs = rhs.to_literal_bits()?;
+                if flags.assume_padding_is_zeroed {
+                    lhs == rhs
+                } else {
+                    Self::literal_eq(ty, lhs, rhs)?
+                }
+                .to_literal_bits()
+            }),
+        })
+    }
+    pub fn lhs(self) -> Expr<CanonicalType> {
+        self.lhs
+    }
+    pub fn rhs(self) -> Expr<CanonicalType> {
+        self.rhs
+    }
+    pub fn flags(self) -> StructuralEqFlags {
+        self.flags
+    }
+}
+
+impl ToLiteralBits for StructuralEq {
+    fn to_literal_bits(&self) -> Result<Interned<BitSlice>, NotALiteralExpr> {
+        self.literal_bits
+    }
+}
+
+impl_get_target_none!([] StructuralEq);
+
+impl ValueType for StructuralEq {
+    type Type = Bool;
+    type ValueCategory = ValueCategoryExpr;
+
+    fn ty(&self) -> Self::Type {
+        Bool
+    }
+}
+
+impl ToExpr for StructuralEq {
+    fn to_expr(&self) -> Expr<Self::Type> {
+        Expr {
+            __enum: ExprEnum::StructuralEq(*self).intern(),
+            __ty: Bool,
+            __flow: Flow::Source,
+        }
+    }
+}

crates/fayalite/src/expr/target.rs

@@ -4,6 +4,7 @@ use crate::{
     array::Array,
     bundle::{Bundle, BundleField},
     expr::{Expr, Flow, ToExpr, ValueType, value_category::ValueCategoryExpr},
+    formal::FormalInput,
     intern::{Intern, Interned},
     memory::{DynPortType, MemPort},
     module::{Instance, ModuleIO, TargetName},
@@ -62,7 +63,7 @@ pub struct TargetPathToTraceAsString {
 
 impl fmt::Display for TargetPathToTraceAsString {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, ".to_trace_as_string(...)")
+        write!(f, ".to_trace_as_string()")
     }
 }
 
@@ -295,6 +296,14 @@ impl_target_base! {
         #[is = is_instance]
         #[to = instance]
         Instance(Instance<Bundle>),
+        #[from = from]
+        #[is = is_formal_input]
+        #[to = formal_input]
+        FormalInput(FormalInput),
+        #[from = from]
+        #[is = is_sim_io_for_global]
+        #[to = sim_io_for_global]
+        SimIoForGlobal(crate::expr::ops::SimIoForGlobal),
     }
 }
 
@@ -343,6 +352,8 @@ impl TargetBase {
             TargetBase::RegAsync(v) => TargetName(v.scoped_name(), None),
             TargetBase::Wire(v) => TargetName(v.scoped_name(), None),
             TargetBase::Instance(v) => TargetName(v.scoped_name(), None),
+            TargetBase::FormalInput(v) => TargetName(v.scoped_name(), None),
+            TargetBase::SimIoForGlobal(v) => TargetName(v.global().scoped_name(), None),
         }
     }
     pub fn canonical_ty(&self) -> CanonicalType {
@@ -354,6 +365,21 @@ impl TargetBase {
             TargetBase::RegAsync(v) => v.ty(),
             TargetBase::Wire(v) => v.ty(),
             TargetBase::Instance(v) => v.ty().canonical(),
+            TargetBase::FormalInput(v) => v.ty(),
+            TargetBase::SimIoForGlobal(v) => v.ty(),
+        }
+    }
+    pub fn is_valid_annotation_target(&self) -> bool {
+        match self {
+            Self::ModuleIO(_) => true,
+            Self::MemPort(_) => true,
+            Self::Reg(_) => true,
+            Self::RegSync(_) => true,
+            Self::RegAsync(_) => true,
+            Self::Wire(_) => true,
+            Self::Instance(_) => true,
+            Self::FormalInput(_) => false,
+            Self::SimIoForGlobal(_) => false,
         }
     }
 }
@@ -548,6 +574,16 @@ impl Target {
             }
         }
     }
+    pub fn is_valid_annotation_target(&self) -> bool {
+        let mut target = self;
+        loop {
+            match target {
+                Self::Base(target_base) => return target_base.is_valid_annotation_target(),
+                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()
@@ -664,6 +700,18 @@ pub trait GetTarget {
     fn target(&self) -> Option<Interned<Target>>;
 }
 
+impl GetTarget for Target {
+    fn target(&self) -> Option<Interned<Target>> {
+        Some(self.intern())
+    }
+}
+
+impl GetTarget for TargetBase {
+    fn target(&self) -> Option<Interned<Target>> {
+        Some(Target::Base(self.intern()).intern_sized())
+    }
+}
+
 impl GetTarget for bool {
     fn target(&self) -> Option<Interned<Target>> {
         None

crates/fayalite/src/formal.rs

@@ -1,11 +1,189 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
+    expr::target::{GetTarget, Target},
     int::BoolOrIntType,
-    intern::{Intern, Interned, Memoize},
+    intern::{Intern, Interned},
+    module::{NameId, NameIdOrGlobal, ScopedNameId},
     prelude::*,
 };
-use std::sync::OnceLock;
+use std::{fmt, sync::OnceLock};
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub enum FormalInputKind {
+    FormalGlobalClock,
+    FormalReset,
+    AnyConst,
+    AnySeq,
+    AllConst,
+    AllSeq,
+}
+
+impl FormalInputKind {
+    pub fn fixed_ty(self) -> Option<CanonicalType> {
+        match self {
+            Self::FormalGlobalClock => Some(Clock.into()),
+            Self::FormalReset => Some(SyncReset.into()),
+            Self::AnyConst => None,
+            Self::AnySeq => None,
+            Self::AllConst => None,
+            Self::AllSeq => None,
+        }
+    }
+    pub fn fixed_id(self) -> Option<crate::module::Id> {
+        struct Cache {
+            formal_global_clock: crate::module::Id,
+            formal_reset: crate::module::Id,
+        }
+        static CACHE: OnceLock<Cache> = OnceLock::new();
+        let cache = || {
+            CACHE.get_or_init(
+                #[cold]
+                || Cache {
+                    formal_global_clock: crate::module::Id::new(),
+                    formal_reset: crate::module::Id::new(),
+                },
+            )
+        };
+        match self {
+            Self::FormalGlobalClock => Some(cache().formal_global_clock),
+            Self::FormalReset => Some(cache().formal_reset),
+            Self::AnyConst => None,
+            Self::AnySeq => None,
+            Self::AllConst => None,
+            Self::AllSeq => None,
+        }
+    }
+    pub fn fixed_source_location(self) -> Option<SourceLocation> {
+        match self {
+            Self::FormalGlobalClock | Self::FormalReset => Some(SourceLocation::builtin()),
+            Self::AnyConst | Self::AnySeq | Self::AllConst | Self::AllSeq => None,
+        }
+    }
+    pub fn name(self) -> &'static str {
+        match self {
+            Self::FormalGlobalClock => "formal_global_clock",
+            Self::FormalReset => "formal_reset",
+            Self::AnyConst => "any_const",
+            Self::AnySeq => "any_seq",
+            Self::AllConst => "all_const",
+            Self::AllSeq => "all_seq",
+        }
+    }
+    pub fn interned_name(self) -> Interned<str> {
+        macro_rules! impl_interned_name {
+            ($($variant:ident,)*) => {
+                match self {
+                    $(Self::$variant => {
+                        static CACHE: OnceLock<Interned<str>> = OnceLock::new();
+                        *CACHE.get_or_init(|| Self::$variant.name().intern())
+                    })*
+                }
+            };
+        }
+        impl_interned_name! {
+            FormalGlobalClock,
+            FormalReset,
+            AnyConst,
+            AnySeq,
+            AllConst,
+            AllSeq,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+struct FormalInputData {
+    kind: FormalInputKind,
+    name_id: NameId,
+    ty: CanonicalType,
+    source_location: SourceLocation,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+pub struct FormalInput(Interned<FormalInputData>);
+
+impl fmt::Debug for FormalInput {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.kind().fixed_ty().is_some() {
+            f.write_str(&self.name())
+        } else {
+            f.debug_tuple(&self.name()).field(&self.0.ty).finish()
+        }
+    }
+}
+
+impl FormalInput {
+    #[track_caller]
+    pub fn new(
+        kind: FormalInputKind,
+        name_id: NameId,
+        ty: CanonicalType,
+        source_location: SourceLocation,
+    ) -> Self {
+        let NameId(name, id) = name_id;
+        assert_eq!(kind.interned_name(), name);
+        if let Some(fixed_ty) = kind.fixed_ty() {
+            assert_eq!(ty, fixed_ty);
+        } else {
+            assert!(
+                ty.is_castable_from_bits(),
+                "{name} type must be castable from bits. got:\n{ty:#?}",
+            );
+        }
+        if let Some(fixed_source_location) = kind.fixed_source_location() {
+            assert_eq!(source_location, fixed_source_location);
+        }
+        if let Some(fixed_id) = kind.fixed_id() {
+            assert_eq!(id, fixed_id);
+        }
+        Self(
+            FormalInputData {
+                kind,
+                name_id,
+                ty,
+                source_location,
+            }
+            .intern_sized(),
+        )
+    }
+    pub fn kind(self) -> FormalInputKind {
+        self.0.kind
+    }
+    pub fn name(self) -> Interned<str> {
+        self.0.name_id.0
+    }
+    pub fn name_id(self) -> NameId {
+        self.0.name_id
+    }
+    pub fn scoped_name(self) -> ScopedNameId {
+        ScopedNameId(NameIdOrGlobal::Global, self.name_id())
+    }
+    pub fn source_location(self) -> SourceLocation {
+        self.0.source_location
+    }
+    pub(crate) fn must_connect_to(self) -> bool {
+        false
+    }
+    pub(crate) fn flow(self) -> crate::expr::Flow {
+        crate::expr::Flow::Source
+    }
+}
+
+impl ValueType for FormalInput {
+    type Type = CanonicalType;
+    type ValueCategory = crate::expr::value_category::ValueCategoryExpr;
+
+    fn ty(&self) -> Self::Type {
+        self.0.ty
+    }
+}
+
+impl GetTarget for FormalInput {
+    fn target(&self) -> Option<Interned<Target>> {
+        Some(Target::from(*self).intern_sized())
+    }
+}
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 pub enum FormalKind {
@@ -138,110 +316,76 @@ make_formal!(
     hdl_cover
 );
 
-pub trait MakeFormalExpr: Type {}
-
-impl<T: Type> MakeFormalExpr for T {}
-
 #[hdl]
 pub fn formal_global_clock() -> Expr<Clock> {
-    #[hdl_module(extern)]
+    static CACHE: OnceLock<Expr<Clock>> = OnceLock::new();
-    fn formal_global_clock() {
+    *CACHE.get_or_init(|| {
-        #[hdl]
+        let kind = FormalInputKind::FormalGlobalClock;
-        let clk: Clock = m.output();
+        Expr::from_canonical(
-        m.annotate_module(BlackBoxInlineAnnotation {
+            FormalInput::new(
-            path: "fayalite_formal_global_clock.v".intern(),
+                kind,
-            text: r"module __fayalite_formal_global_clock(output clk);
+                NameId(
-    (* gclk *)
+                    kind.interned_name(),
-    reg clk;
+                    kind.fixed_id().expect("known to have a fixed Id"),
-endmodule
+                ),
-"
+                Clock.into(),
-            .intern(),
+                kind.fixed_source_location()
-        });
+                    .expect("known to have a fixed SourceLocation"),
-        m.verilog_name("__fayalite_formal_global_clock");
+            )
-    }
+            .to_expr(),
-    #[hdl]
+        )
-    let formal_global_clock = instance(formal_global_clock());
+    })
-    formal_global_clock.clk
 }
 
 #[hdl]
 pub fn formal_reset() -> Expr<SyncReset> {
-    #[hdl_module(extern)]
+    static CACHE: OnceLock<Expr<SyncReset>> = OnceLock::new();
-    fn formal_reset() {
+    *CACHE.get_or_init(|| {
-        #[hdl]
+        let kind = FormalInputKind::FormalReset;
-        let rst: SyncReset = m.output();
+        Expr::from_canonical(
-        m.annotate_module(BlackBoxInlineAnnotation {
+            FormalInput::new(
-            path: "fayalite_formal_reset.v".intern(),
+                kind,
-            text: r"module __fayalite_formal_reset(output rst);
+                NameId(
-    assign rst = $initstate;
+                    kind.interned_name(),
-endmodule
+                    kind.fixed_id().expect("known to have a fixed Id"),
-"
+                ),
-            .intern(),
+                SyncReset.into(),
-        });
+                kind.fixed_source_location()
-        m.verilog_name("__fayalite_formal_reset");
+                    .expect("known to have a fixed SourceLocation"),
-    }
+            )
-    static MOD: OnceLock<Interned<Module<formal_reset>>> = OnceLock::new();
+            .to_expr(),
-    #[hdl]
+        )
-    let formal_reset = instance(*MOD.get_or_init(formal_reset));
+    })
-    formal_reset.rst
 }
 
 macro_rules! make_any_const_fn {
-    ($ident:ident, $verilog_attribute:literal) => {
+    ($ident:ident, $ident_with_loc:ident, $verilog_attribute:literal, $kind:ident) => {
+        #[track_caller]
         #[hdl]
         pub fn $ident<T: BoolOrIntType>(ty: T) -> Expr<T> {
-            #[hdl_module(extern)]
+            $ident_with_loc(ty, SourceLocation::caller())
-            pub(super) fn $ident<T: BoolOrIntType>(ty: T) {
+        }
-                #[hdl]
+        #[track_caller]
-                let out: T = m.output(ty);
+        #[hdl]
-                let width = ty.width();
+        pub fn $ident_with_loc<T: BoolOrIntType>(
-                let verilog_bitslice = if width == 1 {
+            ty: T,
-                    String::new()
+            source_location: SourceLocation,
-                } else {
+        ) -> Expr<T> {
-                    format!(" [{}:0]", width - 1)
+            let kind = FormalInputKind::$kind;
-                };
+            Expr::from_canonical(
-                m.annotate_module(BlackBoxInlineAnnotation {
+                FormalInput::new(
-                    path: Intern::intern_owned(format!(
+                    kind,
-                        "fayalite_{}_{width}.v",
+                    NameId(kind.interned_name(), crate::module::Id::new()),
-                        stringify!($ident),
+                    ty.canonical(),
-                    )),
+                    source_location,
-                    text: Intern::intern_owned(format!(
+                )
-                        r"module __fayalite_{}_{width}(output{verilog_bitslice} out);
+                .to_expr(),
-    (* {} *)
+            )
-    reg{verilog_bitslice} out;
-endmodule
-",
-                        stringify!($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_const, any_const_with_loc, "anyconst", AnyConst);
-make_any_const_fn!(any_seq, "anyseq");
+make_any_const_fn!(any_seq, any_seq_with_loc, "anyseq", AnySeq);
-make_any_const_fn!(all_const, "allconst");
+make_any_const_fn!(all_const, all_const_with_loc, "allconst", AllConst);
-make_any_const_fn!(all_seq, "allseq");
+make_any_const_fn!(all_seq, all_seq_with_loc, "allseq", AllSeq);

crates/fayalite/src/int/uint_in_range.rs

@@ -177,6 +177,8 @@ impl CastToImpl<UIntInRangeMaskType> for Bool {
 }
 
 impl HdlPartialEqImpl<Self> for UIntInRangeMaskType {
+    const TRY_STRUCTURAL_EQ: bool = true;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,
@@ -570,6 +572,8 @@ macro_rules! define_uint_in_range_type {
             HdlPartialEqImpl<$UIntInRangeType<RhsStart, RhsEnd>>
             for $UIntInRangeType<LhsStart, LhsEnd>
         {
+            const TRY_STRUCTURAL_EQ: bool = true;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,
@@ -657,6 +661,8 @@ macro_rules! define_uint_in_range_type {
         impl<Start: Size, End: Size, Width: Size> HdlPartialEqImpl<UIntType<Width>>
             for $UIntInRangeType<Start, End>
         {
+            const TRY_STRUCTURAL_EQ: bool = false;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,
@@ -676,6 +682,8 @@ macro_rules! define_uint_in_range_type {
         impl<Start: Size, End: Size, Width: Size> HdlPartialEqImpl<$UIntInRangeType<Start, End>>
             for UIntType<Width>
         {
+            const TRY_STRUCTURAL_EQ: bool = false;
+
             fn cmp_value_eq(
                 _lhs: Self,
                 lhs_value: Cow<'_, Self::SimValue>,

crates/fayalite/src/intern.rs

@@ -682,27 +682,62 @@ impl<T: ?Sized + 'static + Send + Sync + AsRef<U>, U: ?Sized> AsRef<U> for Inter
 
 #[derive(Clone, Debug)]
 pub struct InternedSliceIter<T: Clone + 'static + Send + Sync> {
-    slice: Interned<[T]>,
+    iter: std::iter::Cloned<std::slice::Iter<'static, T>>,
-    index: std::ops::Range<usize>,
+}
+
+impl<T: Clone + 'static + Send + Sync> Default for InternedSliceIter<T> {
+    fn default() -> Self {
+        Self {
+            iter: [].iter().cloned(),
+        }
+    }
 }
 
 impl<T: Clone + 'static + Send + Sync> Iterator for InternedSliceIter<T> {
     type Item = T;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.index.next().map(|index| self.slice[index].clone())
+        self.iter.next()
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        self.index.size_hint()
+        self.iter.size_hint()
+    }
+
+    fn count(self) -> usize {
+        self.iter.count()
+    }
+
+    fn last(mut self) -> Option<Self::Item> {
+        self.next_back()
+    }
+
+    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+        self.iter.nth(n)
+    }
+
+    fn fold<B, F>(self, init: B, f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.fold(init, f)
     }
 }
 
 impl<T: Clone + 'static + Send + Sync> DoubleEndedIterator for InternedSliceIter<T> {
     fn next_back(&mut self) -> Option<Self::Item> {
-        self.index
+        self.iter.next_back()
-            .next_back()
+    }
-            .map(|index| self.slice[index].clone())
+
+    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+        self.iter.nth_back(n)
+    }
+
+    fn rfold<B, F>(self, init: B, f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        self.iter.rfold(init, f)
     }
 }
 
@@ -716,8 +751,7 @@ impl<T: Clone + 'static + Send + Sync> IntoIterator for Interned<[T]> {
 
     fn into_iter(self) -> Self::IntoIter {
         InternedSliceIter {
-            index: 0..self.len(),
+            iter: Interned::into_inner(self).iter().cloned(),
-            slice: self,
         }
     }
 }

crates/fayalite/src/module.rs

@@ -8,7 +8,7 @@ use crate::{
     clock::{Clock, ClockDomain},
     enum_::{Enum, EnumMatchVariantsIter, EnumType},
     expr::{
-        Expr, Flow, ToExpr, ValueType,
+        Expr, ExprEnum, Flow, ToExpr, ValueType,
         ops::VariantAccess,
         target::{
             GetTarget, Target, TargetBase, TargetPathArrayElement, TargetPathBundleField,
@@ -20,6 +20,7 @@ use crate::{
     int::{Bool, DynSize, Size},
     intern::{Intern, Interned},
     memory::{Mem, MemBuilder, MemBuilderTarget, PortName},
+    module::transform::visit::{Visit, Visitor},
     platform::PlatformIOBuilder,
     reg::Reg,
     reset::{AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset},
@@ -726,7 +727,57 @@ impl fmt::Display for NameId {
 }
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
-pub struct ScopedNameId(pub NameId, pub NameId);
+pub enum NameIdOrGlobal {
+    Global,
+    NameId(NameId),
+}
+
+impl NameIdOrGlobal {
+    pub fn name_id(self) -> Option<NameId> {
+        match self {
+            Self::Global => None,
+            Self::NameId(v) => Some(v),
+        }
+    }
+    #[track_caller]
+    pub fn assert_is_name_id(self) {
+        match self {
+            Self::Global => panic!("expected a NameId, got NameIdOrGlobal::Global"),
+            Self::NameId(_) => {}
+        }
+    }
+    #[track_caller]
+    pub fn unwrap_name_id(self) -> NameId {
+        match self {
+            Self::Global => panic!("expected a NameId, got NameIdOrGlobal::Global"),
+            Self::NameId(v) => v,
+        }
+    }
+}
+
+impl fmt::Debug for NameIdOrGlobal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for NameIdOrGlobal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Global => f.write_str("<<Global>>"),
+            Self::NameId(name_id) => fmt::Display::fmt(name_id, f),
+        }
+    }
+}
+
+impl From<NameId> for NameIdOrGlobal {
+    fn from(value: NameId) -> Self {
+        Self::NameId(value)
+    }
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+pub struct ScopedNameId(pub NameIdOrGlobal, pub NameId);
 
 impl fmt::Debug for ScopedNameId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -804,7 +855,7 @@ impl<T: BundleType> Instance<T> {
         self.containing_module_name_id().0
     }
     pub fn containing_module_name_id(self) -> NameId {
-        self.scoped_name.0
+        self.scoped_name.0.unwrap_name_id()
     }
     pub fn name(self) -> Interned<str> {
         self.name_id().0
@@ -821,11 +872,13 @@ impl<T: BundleType> Instance<T> {
     pub fn source_location(self) -> SourceLocation {
         self.source_location
     }
+    #[track_caller]
     pub fn new_unchecked(
         scoped_name: ScopedNameId,
         instantiated: Interned<Module<T>>,
         source_location: SourceLocation,
     ) -> Self {
+        scoped_name.0.assert_is_name_id();
         Self {
             scoped_name,
             instantiated,
@@ -1598,12 +1651,63 @@ impl TargetState {
     }
 }
 
+struct VisibleExprsStack {
+    buf: Vec<HashSet<ExprEnum>>,
+    len: usize,
+}
+
+impl VisibleExprsStack {
+    fn top(&mut self) -> &mut HashSet<ExprEnum> {
+        &mut self.buf[self.len - 1]
+    }
+    fn slice(&self) -> &[HashSet<ExprEnum>] {
+        &self.buf[..self.len]
+    }
+    fn contains(&self, v: &ExprEnum) -> bool {
+        self.slice().iter().any(|i| i.contains(v))
+    }
+    fn push_empty(&mut self) {
+        #[cold]
+        fn push_empty_cold(stack: &mut VisibleExprsStack) {
+            stack.buf.push(HashSet::default());
+            assert_eq!(stack.buf.len(), stack.len)
+        }
+        self.len += 1;
+        if self.len > self.buf.len() {
+            push_empty_cold(self)
+        }
+    }
+    fn pop(&mut self) {
+        let Some(new_len) = self.len.checked_sub(1) else {
+            unreachable!("visible exprs stack underflow");
+        };
+        self.buf[new_len].clear();
+        self.len = new_len;
+    }
+}
+
+impl Default for VisibleExprsStack {
+    fn default() -> Self {
+        Self {
+            buf: Vec::new(),
+            len: 0,
+        }
+    }
+}
+
 struct AssertValidityState {
     module: Module<Bundle>,
     blocks: Vec<Block>,
+    visible_exprs: VisibleExprsStack,
     target_states: HashMap<Interned<TargetBase>, TargetState>,
 }
 
+enum GetTargetStatesError {
+    NotFound,
+    IsGlobal,
+    FoundSimIoForGlobal(crate::expr::ops::SimIoForGlobal),
+}
+
 impl AssertValidityState {
     fn make_block_index(&mut self, block: Block) -> usize {
         let retval = self.blocks.len();
@@ -1614,7 +1718,7 @@ impl AssertValidityState {
         &'a self,
         target: Target,
         process_target_state: &dyn Fn(&'a TargetState, bool),
-    ) -> Result<(), ()> {
+    ) -> Result<(), GetTargetStatesError> {
         let mut target = target.unwrap_transparent_types();
         loop {
             break match target {
@@ -1667,8 +1771,24 @@ impl AssertValidityState {
             };
         }
     }
-    fn get_base_state(&self, target_base: Interned<TargetBase>) -> Result<&TargetState, ()> {
+    fn get_base_state(
-        self.target_states.get(&target_base).ok_or(())
+        &self,
+        target_base: Interned<TargetBase>,
+    ) -> Result<&TargetState, GetTargetStatesError> {
+        match *target_base {
+            TargetBase::ModuleIO(_)
+            | TargetBase::MemPort(_)
+            | TargetBase::Reg(_)
+            | TargetBase::RegSync(_)
+            | TargetBase::RegAsync(_)
+            | TargetBase::Wire(_)
+            | TargetBase::Instance(_) => self
+                .target_states
+                .get(&target_base)
+                .ok_or(GetTargetStatesError::NotFound),
+            TargetBase::FormalInput(_) => Err(GetTargetStatesError::IsGlobal),
+            TargetBase::SimIoForGlobal(v) => Err(GetTargetStatesError::FoundSimIoForGlobal(v)),
+        }
     }
     #[track_caller]
     fn insert_new_base(&mut self, target_base: Interned<TargetBase>, declared_in_block: usize) {
@@ -1761,16 +1881,30 @@ impl AssertValidityState {
         let result = self.get_target_states(*target, &|target_state, exact_target_unknown| {
             Self::set_connect_target_written(target_state, is_lhs, block, exact_target_unknown);
         });
-        if result.is_err() {
+        match result {
-            if is_lhs {
+            Ok(()) => {}
-                panic!("at {source_location}: tried to connect to not-yet-defined item: {target}");
+            Err(GetTargetStatesError::NotFound) => {
-            } else {
+                if is_lhs {
+                    panic!(
+                        "at {source_location}: tried to connect to not-yet-defined item: {target}"
+                    );
+                } else {
+                    panic!(
+                        "at {source_location}: tried to connect from not-yet-defined item: {target}"
+                    );
+                }
+            }
+            Err(GetTargetStatesError::IsGlobal) => {
+                // no error
+            }
+            Err(GetTargetStatesError::FoundSimIoForGlobal(v)) => {
                 panic!(
-                    "at {source_location}: tried to connect from not-yet-defined item: {target}"
+                    "at {source_location}: fayalite::expr::ops::SimIoForGlobal is not allowed in Modules: {v:?}"
-                );
+                )
             }
         }
     }
+    #[track_caller]
     fn process_conditional_sub_blocks(
         &mut self,
         parent_block: usize,
@@ -1784,17 +1918,40 @@ impl AssertValidityState {
         }
     }
     #[track_caller]
+    fn assert_expr_validity<T: Type>(&mut self, expr: Expr<T>, source_location: SourceLocation) {
+        let mut visitor = AssertExprValidity { state: self };
+        match visitor.visit_expr(&expr) {
+            Ok(()) => {}
+            Err(e) => match e {
+                InvalidExpr::ExprIsNotVisible(expr) => {
+                    if let Some(target) = expr.target() {
+                        panic!(
+                            "at {source_location}: expression isn't visible here, it's defined:\n\
+                            at {}: {expr:?}",
+                            target.base().source_location(),
+                        );
+                    } else {
+                        panic!("at {source_location}: expression isn't visible here: {expr:?}");
+                    }
+                }
+            },
+        }
+    }
+    #[track_caller]
     fn assert_subtree_validity(&mut self, block: usize) {
+        self.visible_exprs.push_empty();
         let module = self.module;
         if block == 0 {
             for module_io in &*module.module_io {
                 self.insert_new_base(TargetBase::intern_sized(module_io.module_io.into()), block);
+                self.visible_exprs.top().insert(module_io.module_io.into());
             }
         }
         let Block { memories, stmts } = self.blocks[block];
         for m in memories {
             for port in m.ports() {
                 self.insert_new_base(TargetBase::intern_sized(port.into()), block);
+                self.visible_exprs.top().insert(port.into());
             }
         }
         for stmt in stmts {
@@ -1808,44 +1965,104 @@ impl AssertValidityState {
                     } = connect;
                     self.set_connect_side_written(lhs, source_location, true, block);
                     self.set_connect_side_written(rhs, source_location, false, block);
+                    self.assert_expr_validity(lhs, source_location);
+                    self.assert_expr_validity(rhs, source_location);
+                }
+                Stmt::Formal(formal) => {
+                    let StmtFormal {
+                        kind: _,
+                        clk,
+                        pred,
+                        en,
+                        text: _,
+                        source_location,
+                    } = formal;
+                    self.assert_expr_validity(clk, source_location);
+                    self.assert_expr_validity(pred, source_location);
+                    self.assert_expr_validity(en, source_location);
                 }
-                Stmt::Formal(_) => {}
                 Stmt::If(if_stmt) => {
-                    let sub_blocks = if_stmt.blocks.map(|block| self.make_block_index(block));
+                    let StmtIf {
+                        cond,
+                        source_location,
+                        blocks: sub_blocks,
+                    } = if_stmt;
+                    self.assert_expr_validity(cond, source_location);
+                    let sub_blocks = sub_blocks.map(|block| self.make_block_index(block));
                     self.process_conditional_sub_blocks(block, sub_blocks)
                 }
                 Stmt::Match(match_stmt) => {
                     match_stmt.assert_validity();
+                    let StmtMatch {
+                        expr,
+                        source_location,
+                        blocks: sub_blocks,
+                    } = match_stmt;
+                    self.assert_expr_validity(expr, source_location);
                     let sub_blocks = Vec::from_iter(
-                        match_stmt
+                        sub_blocks
-                            .blocks
                             .into_iter()
                             .map(|block| self.make_block_index(block)),
                     );
-                    self.process_conditional_sub_blocks(block, sub_blocks.iter().copied())
+                    self.visible_exprs.push_empty();
+                    let visible_exprs_top = self.visible_exprs.top();
+                    for variant_index in 0..expr.ty().variants().len() {
+                        visible_exprs_top
+                            .insert(<VariantAccess>::new_by_index(expr, variant_index).into());
+                    }
+                    self.process_conditional_sub_blocks(block, sub_blocks.iter().copied());
+                    self.visible_exprs.pop();
                 }
                 Stmt::Declaration(StmtDeclaration::Wire(StmtWire {
                     annotations: _,
                     wire,
-                })) => self.insert_new_base(TargetBase::intern_sized(wire.into()), block),
+                })) => {
+                    self.insert_new_base(TargetBase::intern_sized(wire.into()), block);
+                    self.visible_exprs.top().insert(wire.into());
+                }
                 Stmt::Declaration(StmtDeclaration::Reg(StmtReg {
                     annotations: _,
                     reg,
-                })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
+                })) => {
+                    self.assert_expr_validity(reg.clock_domain(), reg.source_location());
+                    if let Some(init) = reg.init() {
+                        self.assert_expr_validity(init, reg.source_location());
+                    }
+                    self.insert_new_base(TargetBase::intern_sized(reg.into()), block);
+                    self.visible_exprs.top().insert(reg.into());
+                }
                 Stmt::Declaration(StmtDeclaration::RegSync(StmtReg {
                     annotations: _,
                     reg,
-                })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
+                })) => {
+                    self.assert_expr_validity(reg.clock_domain(), reg.source_location());
+                    if let Some(init) = reg.init() {
+                        self.assert_expr_validity(init, reg.source_location());
+                    }
+                    self.insert_new_base(TargetBase::intern_sized(reg.into()), block);
+                    self.visible_exprs.top().insert(reg.into());
+                }
                 Stmt::Declaration(StmtDeclaration::RegAsync(StmtReg {
                     annotations: _,
                     reg,
-                })) => self.insert_new_base(TargetBase::intern_sized(reg.into()), block),
+                })) => {
+                    self.assert_expr_validity(reg.clock_domain(), reg.source_location());
+                    if let Some(init) = reg.init() {
+                        self.assert_expr_validity(init, reg.source_location());
+                    }
+                    self.insert_new_base(TargetBase::intern_sized(reg.into()), block);
+                    self.visible_exprs.top().insert(reg.into());
+                }
                 Stmt::Declaration(StmtDeclaration::Instance(StmtInstance {
                     annotations: _,
                     instance,
-                })) => self.insert_new_base(TargetBase::intern_sized(instance.into()), block),
+                })) => {
+                    self.insert_new_base(TargetBase::intern_sized(instance.into()), block);
+                    self.visible_exprs.top().insert(instance.into());
+                }
             }
         }
+        self.visible_exprs.pop();
     }
     #[track_caller]
     fn assert_validity(&mut self) {
@@ -1874,6 +2091,143 @@ impl AssertValidityState {
     }
 }
 
+struct AssertExprValidity<'a> {
+    state: &'a mut AssertValidityState,
+}
+
+enum InvalidExpr {
+    ExprIsNotVisible(Expr<CanonicalType>),
+}
+
+impl transform::visit::Visitor for AssertExprValidity<'_> {
+    type Error = InvalidExpr;
+    fn visit_expr_enum(&mut self, v: &ExprEnum) -> Result<(), Self::Error> {
+        match v {
+            ExprEnum::UIntLiteral(_)
+            | ExprEnum::SIntLiteral(_)
+            | ExprEnum::BoolLiteral(_)
+            | ExprEnum::PhantomConst(_)
+            | ExprEnum::BundleLiteral(_)
+            | ExprEnum::ArrayLiteral(_)
+            | ExprEnum::EnumLiteral(_)
+            | ExprEnum::Uninit(_)
+            | ExprEnum::NotU(_)
+            | ExprEnum::NotS(_)
+            | ExprEnum::NotB(_)
+            | ExprEnum::Neg(_)
+            | ExprEnum::BitAndU(_)
+            | ExprEnum::BitAndS(_)
+            | ExprEnum::BitAndB(_)
+            | ExprEnum::BitOrU(_)
+            | ExprEnum::BitOrS(_)
+            | ExprEnum::BitOrB(_)
+            | ExprEnum::BitXorU(_)
+            | ExprEnum::BitXorS(_)
+            | ExprEnum::BitXorB(_)
+            | ExprEnum::AddU(_)
+            | ExprEnum::AddS(_)
+            | ExprEnum::SubU(_)
+            | ExprEnum::SubS(_)
+            | ExprEnum::MulU(_)
+            | ExprEnum::MulS(_)
+            | ExprEnum::DivU(_)
+            | ExprEnum::DivS(_)
+            | ExprEnum::RemU(_)
+            | ExprEnum::RemS(_)
+            | ExprEnum::DynShlU(_)
+            | ExprEnum::DynShlS(_)
+            | ExprEnum::DynShrU(_)
+            | ExprEnum::DynShrS(_)
+            | ExprEnum::FixedShlU(_)
+            | ExprEnum::FixedShlS(_)
+            | ExprEnum::FixedShrU(_)
+            | ExprEnum::FixedShrS(_)
+            | ExprEnum::CmpLtB(_)
+            | ExprEnum::CmpLeB(_)
+            | ExprEnum::CmpGtB(_)
+            | ExprEnum::CmpGeB(_)
+            | ExprEnum::CmpEqB(_)
+            | ExprEnum::CmpNeB(_)
+            | ExprEnum::CmpLtU(_)
+            | ExprEnum::CmpLeU(_)
+            | ExprEnum::CmpGtU(_)
+            | ExprEnum::CmpGeU(_)
+            | ExprEnum::CmpEqU(_)
+            | ExprEnum::CmpNeU(_)
+            | ExprEnum::CmpLtS(_)
+            | ExprEnum::CmpLeS(_)
+            | ExprEnum::CmpGtS(_)
+            | ExprEnum::CmpGeS(_)
+            | ExprEnum::CmpEqS(_)
+            | ExprEnum::CmpNeS(_)
+            | ExprEnum::CastUIntToUInt(_)
+            | ExprEnum::CastUIntToSInt(_)
+            | ExprEnum::CastSIntToUInt(_)
+            | ExprEnum::CastSIntToSInt(_)
+            | ExprEnum::CastBoolToUInt(_)
+            | ExprEnum::CastBoolToSInt(_)
+            | ExprEnum::CastUIntToBool(_)
+            | ExprEnum::CastSIntToBool(_)
+            | ExprEnum::CastBoolToSyncReset(_)
+            | ExprEnum::CastUIntToSyncReset(_)
+            | ExprEnum::CastSIntToSyncReset(_)
+            | ExprEnum::CastBoolToAsyncReset(_)
+            | ExprEnum::CastUIntToAsyncReset(_)
+            | ExprEnum::CastSIntToAsyncReset(_)
+            | ExprEnum::CastSyncResetToBool(_)
+            | ExprEnum::CastSyncResetToUInt(_)
+            | ExprEnum::CastSyncResetToSInt(_)
+            | ExprEnum::CastSyncResetToReset(_)
+            | ExprEnum::CastAsyncResetToBool(_)
+            | ExprEnum::CastAsyncResetToUInt(_)
+            | ExprEnum::CastAsyncResetToSInt(_)
+            | ExprEnum::CastAsyncResetToReset(_)
+            | ExprEnum::CastResetToBool(_)
+            | ExprEnum::CastResetToUInt(_)
+            | ExprEnum::CastResetToSInt(_)
+            | ExprEnum::CastBoolToClock(_)
+            | ExprEnum::CastUIntToClock(_)
+            | ExprEnum::CastSIntToClock(_)
+            | ExprEnum::CastClockToBool(_)
+            | ExprEnum::CastClockToUInt(_)
+            | ExprEnum::CastClockToSInt(_)
+            | ExprEnum::FieldAccess(_)
+            | ExprEnum::ArrayIndex(_)
+            | ExprEnum::DynArrayIndex(_)
+            | ExprEnum::ReduceBitAndU(_)
+            | ExprEnum::ReduceBitAndS(_)
+            | ExprEnum::ReduceBitOrU(_)
+            | ExprEnum::ReduceBitOrS(_)
+            | ExprEnum::ReduceBitXorU(_)
+            | ExprEnum::ReduceBitXorS(_)
+            | ExprEnum::SliceUInt(_)
+            | ExprEnum::SliceSInt(_)
+            | ExprEnum::CastToBits(_)
+            | ExprEnum::CastBitsTo(_)
+            | ExprEnum::ToTraceAsString(_)
+            | ExprEnum::TraceAsStringAsInner(_)
+            | ExprEnum::StructuralEq(_)
+            | ExprEnum::FormalInput(_) => v.default_visit(self),
+            ExprEnum::VariantAccess(_)
+            | ExprEnum::ModuleIO(_)
+            | ExprEnum::Instance(_)
+            | ExprEnum::Wire(_)
+            | ExprEnum::Reg(_)
+            | ExprEnum::RegSync(_)
+            | ExprEnum::RegAsync(_)
+            | ExprEnum::MemPort(_) => {
+                if self.state.visible_exprs.contains(v) {
+                    // no need to visit inner expressions, we already checked them before adding them to visible_exprs
+                    Ok(())
+                } else {
+                    Err(InvalidExpr::ExprIsNotVisible(v.to_expr()))
+                }
+            }
+            ExprEnum::SimIoForGlobal(_) => Err(InvalidExpr::ExprIsNotVisible(v.to_expr())),
+        }
+    }
+}
+
 impl<T: BundleType> Module<T> {
     /// you generally should use the [`#[hdl_module]`][`crate::hdl_module`] proc-macro and [`ModuleBuilder`] instead
     #[track_caller]
@@ -1894,7 +2248,7 @@ impl<T: BundleType> Module<T> {
                 clocks_for_past,
                 simulation: Some(simulation),
             }) => {
-                let mut clocks_for_past_set = HashSet::default();
+                let mut clocks_for_past_set = HashSet::<Target>::default();
                 *clocks_for_past = clocks_for_past
                     .iter()
                     .copied()
@@ -1915,7 +2269,9 @@ impl<T: BundleType> Module<T> {
                 }
                 if simulation.sim_io_to_generator_map.len() > module_io.len() {
                     // if sim_io_to_generator_map is bigger, then there must be a key that's not in module_io
-                    let module_io_set = HashSet::from_iter(module_io.iter().map(|v| v.module_io));
+                    let module_io_set = HashSet::<ModuleIO<CanonicalType>>::from_iter(
+                        module_io.iter().map(|v| v.module_io),
+                    );
                     for (sim_io, generator_io) in simulation.sim_io_to_generator_map.iter() {
                         if !module_io_set.contains(&**sim_io) {
                             panic!(
@@ -1999,6 +2355,7 @@ impl<T: BundleType> Module<T> {
         AssertValidityState {
             module: self.canonical(),
             blocks: vec![],
+            visible_exprs: VisibleExprsStack::default(),
             target_states: HashMap::with_capacity_and_hasher(64, Default::default()),
         }
         .assert_validity();
@@ -2104,7 +2461,7 @@ impl<T: Type, R: ResetType> RegBuilder<Expr<ClockDomain<R>>, Option<Expr<T>>, T>
             ty,
         } = self;
         ModuleBuilder::with(|module_builder| {
-            let scoped_name = ScopedNameId(module_builder.name, NameId(name, Id::new()));
+            let scoped_name = ScopedNameId(module_builder.name.into(), NameId(name, Id::new()));
             let reg = Reg::new_unchecked(scoped_name, source_location, ty, clock_domain, init);
             let retval = reg.to_expr();
             // convert before borrow_mut since ModuleBuilder could be reentered by T::canonical()
@@ -2500,6 +2857,9 @@ pub fn annotate<T: Type>(target: Expr<T>, annotations: impl IntoAnnotations) {
             instance,
         }
         .into(),
+        TargetBase::FormalInput(_) | TargetBase::SimIoForGlobal(_) => {
+            unreachable!("not a valid annotation target")
+        }
     };
     ModuleBuilder::with(|m| {
         unwrap!(m.impl_.borrow_mut().body.builder_normal_body_opt())
@@ -2514,7 +2874,7 @@ pub fn annotate<T: Type>(target: Expr<T>, annotations: impl IntoAnnotations) {
 #[track_caller]
 pub fn wire_with_loc<T: Type>(name: &str, source_location: SourceLocation, ty: T) -> Expr<T> {
     ModuleBuilder::with(|m| {
-        let scoped_name = ScopedNameId(m.name, NameId(name.intern(), Id::new()));
+        let scoped_name = ScopedNameId(m.name.into(), NameId(name.intern(), Id::new()));
         let wire = Wire::<T>::new_unchecked(scoped_name, source_location, ty);
         let retval = wire.to_expr();
         let canonical_wire = wire.canonical();
@@ -2546,7 +2906,7 @@ fn incomplete_declaration(
     source_location: SourceLocation,
 ) -> Rc<RefCell<IncompleteDeclaration>> {
     ModuleBuilder::with(|m| {
-        let scoped_name = ScopedNameId(m.name, NameId(name.intern(), Id::new()));
+        let scoped_name = ScopedNameId(m.name.into(), NameId(name.intern(), Id::new()));
         let retval = Rc::new(RefCell::new(IncompleteDeclaration::Incomplete {
             name: scoped_name,
             source_location,
@@ -2722,7 +3082,7 @@ pub fn instance_with_loc<T: BundleType>(
     source_location: SourceLocation,
 ) -> Expr<T> {
     ModuleBuilder::with(|m| {
-        let scoped_name = ScopedNameId(m.name, NameId(name.intern(), Id::new()));
+        let scoped_name = ScopedNameId(m.name.into(), NameId(name.intern(), Id::new()));
         let instance = Instance::<T> {
             scoped_name,
             instantiated,
@@ -2761,7 +3121,7 @@ fn memory_impl<Element: Type, Len: Size>(
     source_location: SourceLocation,
 ) -> MemBuilder<Element, Len> {
     ModuleBuilder::with(|m| {
-        let scoped_name = ScopedNameId(m.name, NameId(name.intern(), Id::new()));
+        let scoped_name = ScopedNameId(m.name.into(), NameId(name.intern(), Id::new()));
         let (retval, target_mem) = MemBuilder::new(scoped_name, source_location, mem_element_type);
         let mut impl_ = m.impl_.borrow_mut();
         let body = impl_.body.builder_normal_body();
@@ -2916,7 +3276,7 @@ impl<T: Type> ModuleIO<T> {
         NameId(self.bundle_field.name, self.id)
     }
     pub fn scoped_name(&self) -> ScopedNameId {
-        ScopedNameId(self.containing_module_name, self.name_id())
+        ScopedNameId(self.containing_module_name.into(), self.name_id())
     }
     pub fn source_location(&self) -> SourceLocation {
         self.source_location
@@ -2989,10 +3349,102 @@ impl fmt::Debug for InstantiatedModule {
     }
 }
 
+#[derive(PartialEq, Eq, Hash, Clone, Copy)]
+pub enum InstantiatedModuleOrGlobal {
+    Global,
+    InstantiatedModule(InstantiatedModule),
+}
+
+impl InstantiatedModuleOrGlobal {
+    pub fn leaf_module_source_location(self) -> SourceLocation {
+        match self {
+            Self::Global => SourceLocation::builtin(),
+            Self::InstantiatedModule(v) => v.leaf_module().source_location(),
+        }
+    }
+}
+
+impl From<InstantiatedModule> for InstantiatedModuleOrGlobal {
+    fn from(value: InstantiatedModule) -> Self {
+        Self::InstantiatedModule(value)
+    }
+}
+
+impl fmt::Debug for InstantiatedModuleOrGlobal {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Global => f.write_str("Global"),
+            Self::InstantiatedModule(v) => v.fmt(f),
+        }
+    }
+}
+
 #[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
-pub struct TargetInInstantiatedModule {
+pub struct TargetInInstantiatedModuleOrGlobal {
-    pub instantiated_module: InstantiatedModule,
+    instantiated_module_or_global: InstantiatedModuleOrGlobal,
-    pub target: Target,
+    target: Target,
+}
+
+impl TargetInInstantiatedModuleOrGlobal {
+    #[track_caller]
+    pub fn new(instantiated_module_or_global: InstantiatedModuleOrGlobal, target: Target) -> Self {
+        match (
+            instantiated_module_or_global,
+            target.base().target_name().0.0,
+        ) {
+            (InstantiatedModuleOrGlobal::Global, NameIdOrGlobal::Global)
+            | (InstantiatedModuleOrGlobal::InstantiatedModule(_), NameIdOrGlobal::NameId(_)) => {
+                Self {
+                    instantiated_module_or_global,
+                    target,
+                }
+            }
+            (InstantiatedModuleOrGlobal::Global, NameIdOrGlobal::NameId(_))
+            | (InstantiatedModuleOrGlobal::InstantiatedModule(_), NameIdOrGlobal::Global) => {
+                panic!(
+                    "instantiated_module_or_global doesn't match target.base().target_name().0.0:\n\
+                    instantiated_module_or_global: {instantiated_module_or_global:?}\n\
+                    target: {target:?}"
+                )
+            }
+        }
+    }
+    #[track_caller]
+    pub fn from_target(
+        instantiated_module: impl Into<InstantiatedModuleOrGlobal>,
+        target: Target,
+    ) -> Self {
+        let instantiated_module = instantiated_module.into();
+        Self {
+            instantiated_module_or_global: match target.base().target_name().0.0 {
+                NameIdOrGlobal::Global => InstantiatedModuleOrGlobal::Global,
+                NameIdOrGlobal::NameId(name_id) => {
+                    let InstantiatedModuleOrGlobal::InstantiatedModule(instantiated_module) =
+                        instantiated_module
+                    else {
+                        panic!(
+                            "target is in a module, but no InstantiatedModule was provided: {target:#?}"
+                        );
+                    };
+                    assert_eq!(
+                        name_id,
+                        instantiated_module.leaf_module().name_id(),
+                        "target isn't contained in module:\n\
+                        target: {target:#?}\n\
+                        instantiated_module: {instantiated_module:?}",
+                    );
+                    InstantiatedModuleOrGlobal::InstantiatedModule(instantiated_module)
+                }
+            },
+            target,
+        }
+    }
+    pub fn instantiated_module_or_global(self) -> InstantiatedModuleOrGlobal {
+        self.instantiated_module_or_global
+    }
+    pub fn target(self) -> Target {
+        self.target
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]

crates/fayalite/src/module/transform.rs

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 pub mod deduce_resets;
+pub mod deduce_structural_eq_flags;
 pub mod simplify_enums;
 pub mod simplify_memories;
 pub mod visit;

crates/fayalite/src/module/transform/deduce_resets.rs

@@ -1208,6 +1208,7 @@ impl<P: Pass> RunPass<P> for ExprEnum {
                 Ok(expr.run_pass(pass_args)?.map(ExprEnum::from))
             }
             ExprEnum::ToTraceAsString(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
+            ExprEnum::StructuralEq(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::ModuleIO(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::Instance(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
             ExprEnum::Wire(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
@@ -1215,6 +1216,10 @@ impl<P: Pass> RunPass<P> for ExprEnum {
             ExprEnum::RegSync(expr) => reg_expr_run_pass(expr, pass_args),
             ExprEnum::RegAsync(expr) => reg_expr_run_pass(expr, pass_args),
             ExprEnum::MemPort(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
+            ExprEnum::FormalInput(expr) => Ok(expr.run_pass(pass_args)?.map(ExprEnum::from)),
+            ExprEnum::SimIoForGlobal(_) => {
+                unreachable!("Module is known to not contain SimIoForGlobal from validation")
+            }
         }
     }
 }
@@ -1649,6 +1654,35 @@ impl RunPassExpr for ops::ToTraceAsString {
     }
 }
 
+impl RunPassExpr for ops::StructuralEq {
+    type Args<'a> = [Expr<CanonicalType>; 2];
+
+    fn args<'a>(&'a self) -> Self::Args<'a> {
+        [self.lhs(), self.rhs()]
+    }
+
+    fn source_location(&self) -> Option<SourceLocation> {
+        None
+    }
+
+    fn union_parts(
+        &self,
+        _resets: Resets,
+        args_resets: Vec<Resets>,
+        mut pass_args: PassArgs<'_, BuildResetGraph>,
+    ) -> Result<(), DeduceResetsError> {
+        pass_args.union(args_resets[0], args_resets[1], None)
+    }
+
+    fn new(
+        &self,
+        _ty: CanonicalType,
+        new_args: Vec<Expr<CanonicalType>>,
+    ) -> Result<Self, DeduceResetsError> {
+        Ok(Self::with_flags(new_args[0], new_args[1], self.flags()))
+    }
+}
+
 impl RunPassExpr for ModuleIO<CanonicalType> {
     type Args<'a> = [Expr<CanonicalType>; 0];
 
@@ -1932,6 +1966,7 @@ impl_run_pass_copy!([] SVAttributeAnnotation);
 impl_run_pass_copy!([] UInt);
 impl_run_pass_copy!([] usize);
 impl_run_pass_copy!([] FormalKind);
+impl_run_pass_copy!([] crate::formal::FormalInput);
 impl_run_pass_copy!([] PhantomConst);
 
 macro_rules! impl_run_pass_for_struct {
@@ -2248,6 +2283,12 @@ impl<P: Pass> RunPass<P> for TargetBase {
             &TargetBase::RegAsync(v) => v.into(),
             TargetBase::Wire(v) => return Ok(v.run_pass(pass_args)?.map(TargetBase::Wire)),
             TargetBase::Instance(v) => return Ok(v.run_pass(pass_args)?.map(TargetBase::Instance)),
+            TargetBase::FormalInput(v) => {
+                return Ok(v.run_pass(pass_args)?.map(TargetBase::FormalInput));
+            }
+            TargetBase::SimIoForGlobal(_) => {
+                unreachable!("Module is known to not contain SimIoForGlobal from validation")
+            }
         };
         Ok(reg.run_pass(pass_args)?.map(|reg| match reg {
             AnyReg::Reg(reg) => TargetBase::Reg(reg),

crates/fayalite/src/module/transform/simplify_enums.rs

@@ -1,28 +1,26 @@
 // SPDX-License-Identifier: LGPL-3.0-or-later
 // See Notices.txt for copyright information
 use crate::{
-    array::{Array, ArrayType},
+    bundle::{BundleField, BundleType},
-    bundle::{Bundle, BundleField, BundleType},
+    enum_::{EnumType, EnumVariant},
-    enum_::{Enum, EnumType, EnumVariant},
     expr::{
-        CastBitsTo, CastTo, CastToBits, Expr, ExprEnum, HdlPartialEq, ToExpr, ValueType,
+        ExprEnum,
-        ops::{self, EnumLiteral},
+        ops::{self, EnumLiteral, StructuralEq, StructuralEqFlags},
     },
-    hdl,
-    int::UInt,
     intern::{Intern, InternSlice, Interned, Memoize},
-    memory::{DynPortType, Mem, MemPort},
+    memory::{DynPortType, MemPort},
     module::{
-        Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
+        Block, Id, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
-        transform::visit::{Fold, Folder},
+        transform::{
+            deduce_structural_eq_flags::deduce_structural_eq_flags,
+            visit::{Fold, Folder},
+        },
     },
-    source_location::SourceLocation,
+    prelude::*,
-    ty::{CanonicalType, TraceAsString, Type},
     util::HashMap,
-    wire::Wire,
 };
-use core::fmt;
 use serde::{Deserialize, Serialize};
+use std::fmt;
 
 #[derive(Debug)]
 pub enum SimplifyEnumsError {
@@ -96,11 +94,13 @@ enum EnumTypeState {
 
 struct ModuleState {
     module_name: NameId,
+    expr_cache: HashMap<ExprEnum, ExprEnum>,
+    source_location: SourceLocation,
 }
 
 impl ModuleState {
     fn gen_name(&mut self, name: &str) -> ScopedNameId {
-        ScopedNameId(self.module_name, NameId(name.intern(), Id::new()))
+        ScopedNameId(self.module_name.into(), NameId(name.intern(), Id::new()))
     }
 }
 
@@ -109,6 +109,45 @@ struct State {
     replacement_mem_ports: HashMap<MemPort<DynPortType>, Wire<CanonicalType>>,
     kind: SimplifyEnumsKind,
     module_state_stack: Vec<ModuleState>,
+    new_prefix_stmts_for_block: Vec<Stmt>,
+    new_suffix_stmts_for_block: Vec<Stmt>,
+}
+
+struct BlockScope<'a> {
+    state: &'a mut State,
+    parent_new_prefix_stmts_for_block: Vec<Stmt>,
+    parent_new_suffix_stmts_for_block: Vec<Stmt>,
+}
+
+impl<'a> BlockScope<'a> {
+    fn new(
+        state: &'a mut State,
+        new_prefix_stmts_for_block: Vec<Stmt>,
+        new_suffix_stmts_for_block: Vec<Stmt>,
+    ) -> Self {
+        let parent_new_prefix_stmts_for_block = std::mem::replace(
+            &mut state.new_prefix_stmts_for_block,
+            new_prefix_stmts_for_block,
+        );
+        let parent_new_suffix_stmts_for_block = std::mem::replace(
+            &mut state.new_suffix_stmts_for_block,
+            new_suffix_stmts_for_block,
+        );
+        Self {
+            state,
+            parent_new_prefix_stmts_for_block,
+            parent_new_suffix_stmts_for_block,
+        }
+    }
+}
+
+impl Drop for BlockScope<'_> {
+    fn drop(&mut self) {
+        self.state.new_prefix_stmts_for_block =
+            std::mem::take(&mut self.parent_new_prefix_stmts_for_block);
+        self.state.new_suffix_stmts_for_block =
+            std::mem::take(&mut self.parent_new_suffix_stmts_for_block);
+    }
 }
 
 impl State {
@@ -548,6 +587,185 @@ impl State {
             | CanonicalType::DynSimOnly(_) => unreachable!(),
         }
     }
+    fn handle_enum_structural_eq(
+        &mut self,
+        unfolded_ty: Enum,
+        folded_lhs: Expr<CanonicalType>,
+        folded_rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Expr<Bool>, SimplifyEnumsError> {
+        if flags.assume_padding_is_zeroed {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        let enum_type_state = self.get_or_make_enum_type_state(unfolded_ty)?;
+        if let EnumTypeState::Unchanged = enum_type_state {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        let module_state = self.module_state_stack.last_mut().unwrap();
+        let source_location = module_state.source_location;
+        let output_wire = Wire::new_unchecked(
+            module_state.gen_name("__enum_structural_eq"),
+            source_location,
+            Bool,
+        );
+        self.new_prefix_stmts_for_block.push(
+            StmtWire {
+                annotations: Interned::default(),
+                wire: output_wire.canonical(),
+            }
+            .into(),
+        );
+        let output_wire = output_wire.to_expr();
+        self.new_suffix_stmts_for_block.push(
+            StmtConnect {
+                lhs: Expr::canonical(output_wire),
+                rhs: Expr::canonical(false.to_expr()),
+                source_location,
+            }
+            .into(),
+        );
+        let tags_eq = match enum_type_state {
+            EnumTypeState::TagEnumAndBody(_) => StructuralEq::with_flags(
+                Expr::canonical(Expr::<TagAndBody<Enum, UInt>>::from_canonical(folded_lhs).tag),
+                Expr::canonical(Expr::<TagAndBody<Enum, UInt>>::from_canonical(folded_rhs).tag),
+                StructuralEqFlags {
+                    assume_padding_is_zeroed: true,
+                },
+            )
+            .to_expr(),
+            EnumTypeState::TagUIntAndBody(_) => {
+                let lhs = Expr::<TagAndBody<UInt, UInt>>::from_canonical(folded_lhs).tag;
+                let rhs = Expr::<TagAndBody<UInt, UInt>>::from_canonical(folded_rhs).tag;
+                lhs.cmp_eq(rhs)
+            }
+            EnumTypeState::UInt(_) => {
+                let lhs_int_tag_expr = Expr::<UInt>::from_canonical(folded_lhs)
+                    [..unfolded_ty.discriminant_bit_width()];
+                let rhs_int_tag_expr = Expr::<UInt>::from_canonical(folded_rhs)
+                    [..unfolded_ty.discriminant_bit_width()];
+                lhs_int_tag_expr.cmp_eq(rhs_int_tag_expr)
+            }
+            EnumTypeState::Unchanged => unreachable!(),
+        };
+        let mut match_arms = Vec::with_capacity(unfolded_ty.variants().len());
+        for (variant_index, variant) in unfolded_ty.variants().iter().enumerate() {
+            let block_scope = BlockScope::new(self, vec![], vec![]);
+            let this = &mut *block_scope.state;
+            let eq = if let Some(variant_ty) = variant.ty {
+                let folded_lhs =
+                    this.handle_variant_access(unfolded_ty, folded_lhs, variant_index)?;
+                let folded_rhs =
+                    this.handle_variant_access(unfolded_ty, folded_rhs, variant_index)?;
+                this.handle_structural_eq(variant_ty, folded_lhs, folded_rhs, flags)?
+            } else {
+                true.to_expr()
+            };
+            match_arms.push(Block {
+                memories: [].intern_slice(),
+                stmts: this
+                    .new_prefix_stmts_for_block
+                    .drain(..)
+                    .chain([StmtConnect {
+                        lhs: Expr::canonical(output_wire),
+                        rhs: Expr::canonical(eq),
+                        source_location,
+                    }
+                    .into()])
+                    .chain(this.new_suffix_stmts_for_block.drain(..))
+                    .collect(),
+            });
+        }
+        let match_stmt =
+            self.handle_match(unfolded_ty, folded_lhs, source_location, &match_arms)?;
+        self.new_suffix_stmts_for_block.push(
+            StmtIf {
+                cond: tags_eq,
+                source_location,
+                blocks: [
+                    Block {
+                        memories: [].intern_slice(),
+                        stmts: [match_stmt].intern_slice(),
+                    },
+                    Block {
+                        memories: [].intern_slice(),
+                        stmts: [].intern_slice(),
+                    },
+                ],
+            }
+            .into(),
+        );
+        Ok(output_wire)
+    }
+    fn handle_structural_eq(
+        &mut self,
+        unfolded_ty: CanonicalType,
+        folded_lhs: Expr<CanonicalType>,
+        folded_rhs: Expr<CanonicalType>,
+        flags: StructuralEqFlags,
+    ) -> Result<Expr<Bool>, SimplifyEnumsError> {
+        if !contains_any_enum_types(unfolded_ty) {
+            return Ok(StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr());
+        }
+        match unfolded_ty {
+            CanonicalType::Array(unfolded_ty) => {
+                let unfolded_element_ty = unfolded_ty.element();
+                let mut retval = None;
+                for i in 0..unfolded_ty.len() {
+                    let element_eq = self.handle_structural_eq(
+                        unfolded_element_ty,
+                        ops::ArrayIndex::new(Expr::from_canonical(folded_lhs), i).to_expr(),
+                        ops::ArrayIndex::new(Expr::from_canonical(folded_rhs), i).to_expr(),
+                        flags,
+                    )?;
+                    retval = Some(match retval {
+                        Some(old_eq) => old_eq & element_eq,
+                        None => element_eq,
+                    });
+                }
+                Ok(retval.unwrap_or_else(|| {
+                    StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr()
+                }))
+            }
+            CanonicalType::Enum(unfolded_ty) => {
+                self.handle_enum_structural_eq(unfolded_ty, folded_lhs, folded_rhs, flags)
+            }
+            CanonicalType::Bundle(unfolded_ty) => {
+                let mut retval = None;
+                for (i, field) in unfolded_ty.fields().iter().enumerate() {
+                    let field_eq = self.handle_structural_eq(
+                        field.ty,
+                        ops::FieldAccess::new_by_index(Expr::from_canonical(folded_lhs), i)
+                            .to_expr(),
+                        ops::FieldAccess::new_by_index(Expr::from_canonical(folded_rhs), i)
+                            .to_expr(),
+                        flags,
+                    )?;
+                    retval = Some(match retval {
+                        Some(old_eq) => old_eq & field_eq,
+                        None => field_eq,
+                    });
+                }
+                Ok(retval.unwrap_or_else(|| {
+                    StructuralEq::with_flags(folded_lhs, folded_rhs, flags).to_expr()
+                }))
+            }
+            CanonicalType::TraceAsString(unfolded_ty) => self.handle_structural_eq(
+                unfolded_ty.inner_ty(),
+                *Expr::<TraceAsString>::from_canonical(folded_lhs),
+                *Expr::<TraceAsString>::from_canonical(folded_rhs),
+                flags,
+            ),
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => unreachable!("doesn't contain any enum types"),
+        }
+    }
 }
 
 fn connect_port(
@@ -675,6 +893,8 @@ impl Folder for State {
     fn fold_module<T: BundleType>(&mut self, v: Module<T>) -> Result<Module<T>, Self::Error> {
         self.module_state_stack.push(ModuleState {
             module_name: v.name_id(),
+            expr_cache: HashMap::default(),
+            source_location: v.source_location(),
         });
         let retval = Fold::default_fold(v, self);
         self.module_state_stack.pop();
@@ -682,30 +902,51 @@ impl Folder for State {
     }
 
     fn fold_expr_enum(&mut self, op: ExprEnum) -> Result<ExprEnum, Self::Error> {
-        match op {
+        if let Some(folded_op) = self
+            .module_state_stack
+            .last()
+            .expect("known to be in module")
+            .expr_cache
+            .get(&op)
+        {
+            return Ok(*folded_op);
+        }
+        let folded_op = match op {
             ExprEnum::EnumLiteral(op) => {
                 let folded_variant_value = op.variant_value().map(|v| v.fold(self)).transpose()?;
-                Ok(*Expr::expr_enum(self.handle_enum_literal(
+                *Expr::expr_enum(self.handle_enum_literal(
                     op.ty(),
                     op.variant_index(),
                     folded_variant_value,
-                )?))
+                )?)
             }
             ExprEnum::VariantAccess(op) => {
                 let folded_base_expr = Expr::canonical(op.base()).fold(self)?;
-                Ok(*Expr::expr_enum(self.handle_variant_access(
+                *Expr::expr_enum(self.handle_variant_access(
                     op.base().ty(),
                     folded_base_expr,
                     op.variant_index(),
-                )?))
+                )?)
             }
-            ExprEnum::MemPort(mem_port) => Ok(
+            ExprEnum::StructuralEq(op) => {
+                let ty = op.lhs().ty();
+                assert_eq!(ty, op.rhs().ty());
+                let folded_lhs = Expr::canonical(op.lhs()).fold(self)?;
+                let folded_rhs = Expr::canonical(op.rhs()).fold(self)?;
+                *Expr::expr_enum(self.handle_structural_eq(
+                    ty,
+                    folded_lhs,
+                    folded_rhs,
+                    op.flags(),
+                )?)
+            }
+            ExprEnum::MemPort(mem_port) => {
                 if let Some(&wire) = self.replacement_mem_ports.get(&mem_port) {
                     ExprEnum::Wire(wire)
                 } else {
                     ExprEnum::MemPort(mem_port.fold(self)?)
-                },
+                }
-            ),
+            }
             ExprEnum::UIntLiteral(_)
             | ExprEnum::SIntLiteral(_)
             | ExprEnum::BoolLiteral(_)
@@ -813,16 +1054,26 @@ impl Folder for State {
             | ExprEnum::Wire(_)
             | ExprEnum::Reg(_)
             | ExprEnum::RegSync(_)
-            | ExprEnum::RegAsync(_) => op.default_fold(self),
+            | ExprEnum::RegAsync(_)
-        }
+            | ExprEnum::FormalInput(_)
+            | ExprEnum::SimIoForGlobal(_) => op.default_fold(self)?,
+        };
+        self.module_state_stack
+            .last_mut()
+            .expect("known to be in module")
+            .expr_cache
+            .insert(op, folded_op);
+        Ok(folded_op)
     }
 
     fn fold_block(&mut self, block: Block) -> Result<Block, Self::Error> {
+        let block_scope = BlockScope::new(self, vec![], vec![]);
+        let this = &mut *block_scope.state;
         let mut memories = vec![];
         let mut stmts = vec![];
         for memory in block.memories {
             let old_element_ty = memory.array_type().element();
-            let new_element_ty = memory.array_type().element().fold(self)?;
+            let new_element_ty = memory.array_type().element().fold(this)?;
             if new_element_ty != old_element_ty {
                 let mut new_ports = vec![];
                 for port in memory.ports() {
@@ -848,7 +1099,7 @@ impl Folder for State {
                         continue;
                     }
                     let wire = Wire::new_unchecked(
-                        self.module_state_stack
+                        this.module_state_stack
                             .last_mut()
                             .unwrap()
                             .gen_name(&format!(
@@ -872,7 +1123,7 @@ impl Folder for State {
                         Expr::canonical(wire.to_expr()),
                         port.source_location(),
                     );
-                    self.replacement_mem_ports.insert(port, wire.canonical());
+                    this.replacement_mem_ports.insert(port, wire.canonical());
                 }
                 memories.push(Mem::new_unchecked(
                     memory.scoped_name(),
@@ -887,10 +1138,12 @@ impl Folder for State {
                     memory.mem_annotations(),
                 ));
             } else {
-                memories.push(memory.fold(self)?);
+                memories.push(memory.fold(this)?);
             }
         }
-        stmts.extend_from_slice(&block.stmts.fold(self)?);
+        stmts.extend_from_slice(&block.stmts.fold(this)?);
+        stmts.splice(0..0, this.new_prefix_stmts_for_block.drain(..));
+        stmts.extend_from_slice(&this.new_suffix_stmts_for_block);
         Ok(Block {
             memories: Intern::intern_owned(memories),
             stmts: Intern::intern_owned(stmts),
@@ -1012,10 +1265,13 @@ pub fn simplify_enums(
     module: Interned<Module<Bundle>>,
     kind: SimplifyEnumsKind,
 ) -> Result<Interned<Module<Bundle>>, SimplifyEnumsError> {
+    let module = deduce_structural_eq_flags(module);
     module.fold(&mut State {
         enum_types: HashMap::default(),
         replacement_mem_ports: HashMap::default(),
         kind,
         module_state_stack: vec![],
+        new_prefix_stmts_for_block: vec![],
+        new_suffix_stmts_for_block: vec![],
     })
 }

crates/fayalite/src/module/transform/visit.rs

@@ -18,13 +18,13 @@ use crate::{
             TargetPathTraceAsStringInner,
         },
     },
-    formal::FormalKind,
+    formal::{FormalInput, FormalInputKind, 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,
+        ExternModuleParameterValue, Instance, Module, ModuleBody, ModuleIO, NameId, NameIdOrGlobal,
         NormalModuleBody, ScopedNameId, Stmt, StmtConnect, StmtDeclaration, StmtFormal, StmtIf,
         StmtInstance, StmtMatch, StmtReg, StmtWire,
     },
@@ -482,4 +482,30 @@ impl<T: ?Sized + Visit<State>, State: ?Sized + Visitor> Visit<State> for &'_ mut
     }
 }
 
+impl<State: ?Sized + Visitor> Visit<State> for NameIdOrGlobal {
+    fn visit(&self, state: &mut State) -> Result<(), <State>::Error> {
+        state.visit_name_id_or_global(self)
+    }
+
+    fn default_visit(&self, state: &mut State) -> Result<(), <State>::Error> {
+        match self {
+            Self::Global => Ok(()),
+            Self::NameId(name_id) => name_id.visit(state),
+        }
+    }
+}
+
+impl<State: ?Sized + Folder> Fold<State> for NameIdOrGlobal {
+    fn fold(self, state: &mut State) -> Result<Self, <State>::Error> {
+        state.fold_name_id_or_global(self)
+    }
+
+    fn default_fold(self, state: &mut State) -> Result<Self, <State>::Error> {
+        match self {
+            Self::Global => Ok(Self::Global),
+            Self::NameId(name_id) => Ok(Self::NameId(name_id.fold(state)?)),
+        }
+    }
+}
+
 include!(concat!(env!("OUT_DIR"), "/visit.rs"));

crates/fayalite/src/phantom_const.rs

@@ -384,6 +384,8 @@ impl<'de, T: ?Sized + PhantomConstValue> Deserialize<'de> for PhantomConst<T> {
 }
 
 impl<T: ?Sized + PhantomConstValue> HdlPartialEqImpl<Self> for PhantomConst<T> {
+    const TRY_STRUCTURAL_EQ: bool = true;
+
     #[track_caller]
     fn cmp_value_eq(
         lhs: Self,

crates/fayalite/src/prelude.rs

@@ -16,8 +16,8 @@ pub use crate::{
         ReduceBits, ToExpr, ToTraceAsString, ValueType, repeat,
     },
     formal::{
-        MakeFormalExpr, all_const, all_seq, any_const, any_seq, formal_global_clock, formal_reset,
+        all_const, all_seq, any_const, any_seq, formal_global_clock, formal_reset, hdl_assert,
-        hdl_assert, hdl_assert_with_enable, hdl_assume, hdl_assume_with_enable, hdl_cover,
+        hdl_assert_with_enable, hdl_assume, hdl_assume_with_enable, hdl_cover,
         hdl_cover_with_enable,
     },
     hdl, hdl_module,
@@ -37,7 +37,7 @@ pub use crate::{
         value::{SimOnly, SimOnlyValue, SimValue, ToSimValue, ToSimValueWithType},
     },
     source_location::SourceLocation,
-    testing::{FormalMode, assert_formal},
+    testing::{FormalMode, assert_formal, checked_vcd_output},
     ty::{AsMask, CanonicalType, TraceAsString, Type},
     util::{ConstUsize, GenericConstUsize},
     wire::Wire,

crates/fayalite/src/reg.rs

@@ -79,6 +79,7 @@ impl<T: Type, R: ResetType> Reg<T, R> {
         if let Some(init) = init {
             assert_eq!(ty, init.ty(), "register's type must match init type");
         }
+        scoped_name.0.assert_is_name_id();
         Self {
             name: scoped_name,
             source_location,
@@ -94,7 +95,7 @@ impl<T: Type, R: ResetType> Reg<T, R> {
         self.containing_module_name_id().0
     }
     pub fn containing_module_name_id(&self) -> NameId {
-        self.name.0
+        self.name.0.unwrap_name_id()
     }
     pub fn name(&self) -> Interned<str> {
         self.name_id().0

crates/fayalite/src/sim.rs

@@ -6,26 +6,29 @@
 use crate::{
     bundle::{BundleField, BundleType},
     expr::{
-        Flow,
+        ExprEnum, Flow,
+        ops::SimIoForGlobal,
         target::{
-            GetTarget, Target, TargetPathArrayElement, TargetPathBundleField, TargetPathElement,
+            GetTarget, Target, TargetBase, TargetChild, TargetPathArrayElement,
-            TargetPathTraceAsStringInner,
+            TargetPathBundleField, TargetPathElement, TargetPathTraceAsStringInner,
         },
     },
+    formal::FormalInput,
     int::BoolOrIntType,
     intern::{
-        Intern, InternSlice, Interned, InternedCompare, PtrEqWithTypeId, SupportsPtrEqWithTypeId,
+        Intern, InternSlice, Interned, InternedCompare, InternedSliceIter, Memoize,
+        PtrEqWithTypeId, SupportsPtrEqWithTypeId,
     },
     module::{
-        ModuleIO,
+        ModuleIO, StmtFormal,
         transform::visit::{Fold, Folder, Visit, Visitor},
     },
     prelude::*,
     reset::ResetType,
     sim::{
         compiler::{
-            Compiled, CompiledBundleField, CompiledExternModule, CompiledTypeLayoutBody,
+            Compiled, CompiledAssert, CompiledBundleField, CompiledExternModule,
-            CompiledValue, ExternModuleClockForPast,
+            CompiledTypeLayoutBody, CompiledValue, ExternModuleClockForPast,
         },
         interpreter::{
             BreakAction, BreakpointsSet, RunResult, SmallUInt, State,
@@ -50,7 +53,7 @@ use std::{
     any::Any,
     cell::{Cell, RefCell},
     collections::{BTreeMap, BTreeSet},
-    fmt,
+    fmt::{self, Write},
     future::{Future, IntoFuture},
     hash::Hash,
     mem,
@@ -315,6 +318,14 @@ impl_trace_decl! {
             ty: CanonicalType,
             flow: Flow,
         }),
+        FormalInput(TraceFormalInput {
+            fn children(self) -> _ {
+                [*self.child].intern_slice()
+            }
+            name: Interned<str>,
+            child: Interned<TraceDecl>,
+            formal_input: FormalInput,
+        }),
         Bundle(TraceBundle {
             fn children(self) -> _ {
                 self.fields
@@ -1288,9 +1299,14 @@ impl SimulationModuleState {
     #[track_caller]
     fn get_io(
         &self,
-        mut target: Target,
+        target: &mut Interned<Target>,
-        which_module: WhichModule,
+        which_module: WhichModule<'_>,
     ) -> CompiledValue<CanonicalType> {
+        match which_module {
+            WhichModule::Main { global_io } => *target = global_io.to_sim_io_target(*target),
+            WhichModule::Extern { .. } => {}
+        }
+        let mut target = **target;
         assert!(
             target.canonical_ty().is_passive(),
             "simulator read/write expression must have a passive type \
@@ -1317,9 +1333,9 @@ impl SimulationModuleState {
             };
         }
         match which_module {
-            WhichModule::Main => panic!(
+            WhichModule::Main { .. } => panic!(
                 "simulator read/write expression must be \
-                an array element/field of `Simulation::io()`"
+                an array element/field of `Simulation::io()` or `Simulation::global_io()`"
             ),
             WhichModule::Extern { .. } => panic!(
                 "simulator read/write expression must be \
@@ -1329,18 +1345,18 @@ impl SimulationModuleState {
         }
     }
     #[track_caller]
-    fn is_reset_async(&self, io: Expr<CanonicalType>, which_module: WhichModule) -> bool {
+    fn is_reset_async(&self, io: Expr<CanonicalType>, which_module: WhichModule<'_>) -> bool {
-        let Some(target) = io.target() else {
+        let Some(mut target) = io.target() else {
             match which_module {
-                WhichModule::Main => panic!(
+                WhichModule::Main { .. } => panic!(
-                    "can't read from an expression that's not a field/element of `Simulation::io()`"
+                    "can't read from an expression that's not a field/element of `Simulation::io()` or `Simulation::global_io()`"
                 ),
                 WhichModule::Extern { .. } => panic!(
                     "can't read from an expression that's not based on one of this module's inputs/outputs"
                 ),
             }
         };
-        match self.get_io(*target, which_module).layout.ty {
+        match self.get_io(&mut target, which_module).layout.ty {
             CanonicalType::UInt(_)
             | CanonicalType::SInt(_)
             | CanonicalType::Bool(_)
@@ -1360,24 +1376,24 @@ impl SimulationModuleState {
     fn read_helper_current(
         &self,
         io: Expr<CanonicalType>,
-        which_module: WhichModule,
+        which_module: WhichModule<'_>,
     ) -> MaybeNeedsSettle<CompiledValue<CanonicalType>> {
-        let Some(target) = io.target() else {
+        let Some(mut target) = io.target() else {
             match which_module {
-                WhichModule::Main => panic!(
+                WhichModule::Main { .. } => panic!(
-                    "can't read from an expression that's not a field/element of `Simulation::io()`"
+                    "can't read from an expression that's not a field/element of `Simulation::io()` or `Simulation::global_io()`"
                 ),
                 WhichModule::Extern { .. } => panic!(
                     "can't read from an expression that's not based on one of this module's inputs/outputs"
                 ),
             }
         };
-        let compiled_value = self.get_io(*target, which_module);
+        let compiled_value = self.get_io(&mut target, which_module);
         match target.flow() {
             Flow::Source => {
                 if !self.uninitialized_ios.is_empty() {
                     match which_module {
-                        WhichModule::Main => {
+                        WhichModule::Main { .. } => {
                             panic!(
                                 "can't read from an output before initializing all inputs\nuninitialized_ios={:#?}",
                                 SortedSetDebug(&self.uninitialized_ios),
@@ -1396,7 +1412,9 @@ impl SimulationModuleState {
             Flow::Sink => {
                 if self.uninitialized_ios.contains_key(&*target) {
                     match which_module {
-                        WhichModule::Main => panic!("can't read from an uninitialized input"),
+                        WhichModule::Main { .. } => {
+                            panic!("can't read from an uninitialized input")
+                        }
                         WhichModule::Extern { .. } => {
                             panic!("can't read from an uninitialized output");
                         }
@@ -1412,7 +1430,7 @@ impl SimulationModuleState {
         &self,
         io: Expr<CanonicalType>,
         read_time: ReadTime,
-        which_module: WhichModule,
+        which_module: WhichModule<'_>,
     ) -> MaybeNeedsSettle<CompiledValue<CanonicalType>> {
         match read_time {
             ReadTime::Current => self.read_helper_current(io, which_module),
@@ -1438,22 +1456,22 @@ impl SimulationModuleState {
     fn write_helper(
         &mut self,
         io: Expr<CanonicalType>,
-        which_module: WhichModule,
+        which_module: WhichModule<'_>,
     ) -> CompiledValue<CanonicalType> {
-        let Some(target) = io.target() else {
+        let Some(mut target) = io.target() else {
             match which_module {
-                WhichModule::Main => panic!(
+                WhichModule::Main { .. } => panic!(
-                    "can't write to an expression that's not a field/element of `Simulation::io()`"
+                    "can't write to an expression that's not a field/element of `Simulation::io()` or `Simulation::global_io()`"
                 ),
                 WhichModule::Extern { .. } => panic!(
                     "can't write to an expression that's not based on one of this module's outputs"
                 ),
             }
         };
-        let compiled_value = self.get_io(*target, which_module);
+        let compiled_value = self.get_io(&mut target, which_module);
         match target.flow() {
             Flow::Source => match which_module {
-                WhichModule::Main => panic!("can't write to an output"),
+                WhichModule::Main { .. } => panic!("can't write to an output"),
                 WhichModule::Extern { .. } => panic!("can't write to an input"),
             },
             Flow::Sink => {}
@@ -1573,9 +1591,9 @@ impl fmt::Debug for SimulationExternModuleState {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone)]
-enum WhichModule {
+enum WhichModule<'a> {
-    Main,
+    Main { global_io: &'a SimulationGlobalIo },
     Extern { module_index: usize },
 }
 
@@ -1986,6 +2004,7 @@ impl SensitivitySet {
 struct SimulationImpl {
     state: interpreter::State,
     io: Expr<Bundle>,
+    global_io: SimulationGlobalIo,
     main_module: SimulationModuleState,
     extern_modules: Box<[SimulationExternModuleState]>,
     trace_decls: TraceModule,
@@ -2005,6 +2024,7 @@ struct SimulationImpl {
     >,
     waiting_sensitivity_sets_by_address: HashMap<*const SensitivitySet, Rc<SensitivitySet>>,
     trace_as_string_buf: String,
+    asserts: Interned<[CompiledAssert]>,
 }
 
 impl fmt::Debug for SimulationImpl {
@@ -2082,6 +2102,7 @@ impl SimulationImpl {
         let Self {
             state,
             io: self_io,
+            global_io,
             main_module,
             extern_modules,
             trace_decls,
@@ -2095,10 +2116,15 @@ impl SimulationImpl {
             waiting_sensitivity_sets_by_compiled_value,
             waiting_sensitivity_sets_by_address,
             trace_as_string_buf: _,
+            asserts,
         } = self;
         f.debug_struct("Simulation")
             .field("state", state)
             .field("io", io.unwrap_or(self_io))
+            .field(
+                "global_io",
+                &fmt::from_fn(|f| f.debug_map().entries(global_io.global_io).finish()),
+            )
             .field("main_module", main_module)
             .field("extern_modules", extern_modules)
             .field("trace_decls", trace_decls)
@@ -2118,6 +2144,7 @@ impl SimulationImpl {
                 "waiting_sensitivity_sets_by_compiled_value",
                 &DebugSensitivitySetsByCompiledValue(waiting_sensitivity_sets_by_compiled_value),
             )
+            .field("asserts", asserts)
             .finish_non_exhaustive()
     }
     fn new(compiled: Compiled<Bundle>) -> Self {
@@ -2160,22 +2187,29 @@ impl SimulationImpl {
         Self {
             state: State::new(compiled.insns),
             io: compiled.io.to_expr(),
+            global_io: SimulationGlobalIo::new(compiled.global_io),
             main_module: SimulationModuleState::new(
                 compiled
-                    .io
+                    .global_io
-                    .ty()
+                    .iter()
-                    .fields()
+                    .map(|&(global_io, value)| (global_io.into(), value))
-                    .into_iter()
+                    .chain(
-                    .zip(compiled.base_module.module_io)
+                        compiled
-                    .map(|(BundleField { name, .. }, value)| {
+                            .io
-                        (
+                            .ty()
-                            io_target.join(
+                            .fields()
-                                TargetPathElement::from(TargetPathBundleField { name })
+                            .into_iter()
-                                    .intern_sized(),
+                            .zip(compiled.base_module.module_io)
-                            ),
+                            .map(|(BundleField { name, .. }, value)| {
-                            value,
+                                (
-                        )
+                                    io_target.join(
-                    }),
+                                        TargetPathElement::from(TargetPathBundleField { name })
+                                            .intern_sized(),
+                                    ),
+                                    value,
+                                )
+                            }),
+                    ),
                 &[],
             ),
             extern_modules,
@@ -2202,6 +2236,7 @@ impl SimulationImpl {
             waiting_sensitivity_sets_by_compiled_value: HashMap::default(),
             waiting_sensitivity_sets_by_address: HashMap::default(),
             trace_as_string_buf: String::with_capacity(256),
+            asserts: compiled.asserts,
         }
     }
     fn write_traces<const ONLY_IF_CHANGED: bool>(
@@ -2729,6 +2764,50 @@ impl SimulationImpl {
             self.cancel_wake_after_change(&sensitivity_set);
         }
     }
+    #[track_caller]
+    #[cold]
+    fn handle_failed_asserts(&mut self, assert_failed_log: Vec<usize>) -> ! {
+        let mut message = format!(
+            "Assertions/Assumptions failed at time {:?}:\n",
+            self.event_queue.lock().instant,
+        );
+        for assert_failed_index in assert_failed_log {
+            let CompiledAssert {
+                instantiated_module,
+                stmt_formal:
+                    StmtFormal {
+                        kind,
+                        clk: _,
+                        pred: _,
+                        en: _,
+                        text,
+                        source_location,
+                    },
+            } = self.asserts[assert_failed_index];
+            writeln!(
+                message,
+                "at {source_location}: in {instantiated_module:?}: {} failed: {text}",
+                kind.as_str()
+            )
+            .unwrap();
+        }
+        panic!("{message}")
+    }
+    #[track_caller]
+    fn check_for_failed_asserts(&mut self) {
+        if self.state.assert_failed_log.is_empty() {
+            return;
+        }
+        if let Some(Event {
+            instant: _,
+            kind: EventKind::State,
+        }) = self.event_queue.peek_first_event_for_now()
+        {
+            return;
+        }
+        let assert_failed_log = mem::take(&mut self.state.assert_failed_log);
+        self.handle_failed_asserts(assert_failed_log);
+    }
     fn write_traces_after_event(&mut self) {
         if let Some(Event {
             instant: _,
@@ -2831,6 +2910,7 @@ impl SimulationImpl {
                     }
                 }
                 this.write_traces_after_event();
+                this.check_for_failed_asserts();
                 this.check_waiting_sensitivity_sets();
             } else {
                 event_queue = first_entry.into_event_queue_lock();
@@ -2852,18 +2932,23 @@ impl SimulationImpl {
     fn settle(this_ref: &Rc<RefCell<Self>>) {
         Self::run_until(this_ref, &mut Some);
     }
-    fn get_module(&self, which_module: WhichModule) -> &SimulationModuleState {
+    fn get_module(&self, which_module: WhichModule<'_>) -> &SimulationModuleState {
         match which_module {
-            WhichModule::Main => &self.main_module,
+            WhichModule::Main { .. } => &self.main_module,
             WhichModule::Extern { module_index } => &self.extern_modules[module_index].module_state,
         }
     }
-    fn get_module_mut(&mut self, which_module: WhichModule) -> &mut SimulationModuleState {
+    fn get_module_mut_and_which_module(
+        &mut self,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
+    ) -> (&mut SimulationModuleState, WhichModule<'_>) {
+        let which_module = which_module(&self.global_io);
         match which_module {
-            WhichModule::Main => &mut self.main_module,
+            WhichModule::Main { .. } => (&mut self.main_module, which_module),
-            WhichModule::Extern { module_index } => {
+            WhichModule::Extern { module_index } => (
-                &mut self.extern_modules[module_index].module_state
+                &mut self.extern_modules[module_index].module_state,
-            }
+                which_module,
+            ),
         }
     }
     #[track_caller]
@@ -2871,18 +2956,23 @@ impl SimulationImpl {
         &mut self,
         io: Expr<CanonicalType>,
         read_time: ReadTime,
-        which_module: WhichModule,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
     ) -> MaybeNeedsSettle<ReadBitFn, bool> {
+        let which_module = which_module(&self.global_io);
         self.get_module(which_module)
             .read_helper(Expr::canonical(io), read_time, which_module)
             .map(|compiled_value| ReadBitFn { compiled_value })
             .apply_no_settle(&mut self.state)
     }
     #[track_caller]
-    fn write_bit(&mut self, io: Expr<CanonicalType>, value: bool, which_module: WhichModule) {
+    fn write_bit(
-        let compiled_value = self
+        &mut self,
-            .get_module_mut(which_module)
+        io: Expr<CanonicalType>,
-            .write_helper(io, which_module);
+        value: bool,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
+    ) {
+        let (module, which_module) = self.get_module_mut_and_which_module(which_module);
+        let compiled_value = module.write_helper(io, which_module);
         self.event_queue.add_event_for_now(EventKind::State);
         match compiled_value.range.len().as_single() {
             Some(TypeLenSingle::SmallSlot) => {
@@ -2900,8 +2990,9 @@ impl SimulationImpl {
         &mut self,
         io: Expr<I>,
         read_time: ReadTime,
-        which_module: WhichModule,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
     ) -> MaybeNeedsSettle<ReadBoolOrIntFn<I>, I::Value> {
+        let which_module = which_module(&self.global_io);
         self.get_module(which_module)
             .read_helper(Expr::canonical(io), read_time, which_module)
             .map(|compiled_value| ReadBoolOrIntFn { compiled_value, io })
@@ -2912,11 +3003,10 @@ impl SimulationImpl {
         &mut self,
         io: Expr<I>,
         value: I::Value,
-        which_module: WhichModule,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
     ) {
-        let compiled_value = self
+        let (module, which_module) = self.get_module_mut_and_which_module(which_module);
-            .get_module_mut(which_module)
+        let compiled_value = module.write_helper(Expr::canonical(io), which_module);
-            .write_helper(Expr::canonical(io), which_module);
         self.event_queue.add_event_for_now(EventKind::State);
         let value: BigInt = value.into();
         match compiled_value.range.len().as_single() {
@@ -3148,7 +3238,12 @@ impl SimulationImpl {
         any_change.get()
     }
     #[track_caller]
-    fn is_reset_async(&self, io: Expr<CanonicalType>, which_module: WhichModule) -> bool {
+    fn is_reset_async(
+        &self,
+        io: Expr<CanonicalType>,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
+    ) -> bool {
+        let which_module = which_module(&self.global_io);
         self.get_module(which_module)
             .is_reset_async(io, which_module)
     }
@@ -3157,11 +3252,12 @@ impl SimulationImpl {
         &mut self,
         io: Expr<CanonicalType>,
         read_time: ReadTime,
-        which_module: WhichModule,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
     ) -> (
         CompiledValue<CanonicalType>,
         MaybeNeedsSettle<ReadFn, SimValue<CanonicalType>>,
     ) {
+        let which_module = which_module(&self.global_io);
         let compiled_value = self
             .get_module(which_module)
             .read_helper(io, read_time, which_module);
@@ -3189,11 +3285,10 @@ impl SimulationImpl {
         &mut self,
         io: Expr<CanonicalType>,
         value: &SimValue<CanonicalType>,
-        which_module: WhichModule,
+        which_module: impl for<'a> Fn(&'a SimulationGlobalIo) -> WhichModule<'a>,
     ) {
-        let compiled_value = self
+        let (module, which_module) = self.get_module_mut_and_which_module(which_module);
-            .get_module_mut(which_module)
+        let compiled_value = module.write_helper(io, which_module);
-            .write_helper(io, which_module);
         self.event_queue.add_event_for_now(EventKind::State);
         assert_eq!(io.ty(), value.ty());
         Self::read_write_sim_value_helper(
@@ -3370,6 +3465,318 @@ impl Drop for SimulationImpl {
     }
 }
 
+#[derive(Clone)]
+pub struct SimulationGlobalIo {
+    global_io: Interned<[(SimIoForGlobal, CompiledValue<CanonicalType>)]>,
+    global_io_map: Rc<HashMap<SimIoForGlobal, usize>>,
+}
+
+impl Default for SimulationGlobalIo {
+    fn default() -> Self {
+        Self {
+            global_io: Interned::default(),
+            global_io_map: Rc::default(),
+        }
+    }
+}
+
+impl fmt::Debug for SimulationGlobalIo {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_map().entries(self.global_io).finish()
+    }
+}
+
+impl SimulationGlobalIo {
+    fn new(global_io: Interned<[(SimIoForGlobal, CompiledValue<CanonicalType>)]>) -> Self {
+        Self {
+            global_io,
+            global_io_map: Rc::new(HashMap::from_iter(
+                global_io
+                    .iter()
+                    .enumerate()
+                    .map(|(index, &(global, _))| (global, index)),
+            )),
+        }
+    }
+    #[must_use]
+    pub fn iter(&self) -> SimulationGlobalIoIter {
+        SimulationGlobalIoIter {
+            global_io: self.global_io.into_iter(),
+        }
+    }
+    #[must_use]
+    pub fn globals(&self) -> SimulationGlobalIoGlobalsIter {
+        SimulationGlobalIoGlobalsIter {
+            global_io: self.global_io.into_iter(),
+        }
+    }
+    #[must_use]
+    pub fn exprs(&self) -> SimulationGlobalIoExprsIter {
+        SimulationGlobalIoExprsIter {
+            global_io: self.global_io.into_iter(),
+        }
+    }
+    #[must_use]
+    pub fn len(&self) -> usize {
+        self.global_io.len()
+    }
+    #[must_use]
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+    #[must_use]
+    pub fn contains(&self, global: FormalInput) -> bool {
+        self.global_io_map
+            .contains_key(&SimIoForGlobal::new(global))
+    }
+    #[must_use]
+    pub fn get(&self, global: FormalInput) -> Option<Expr<CanonicalType>> {
+        self.contains(global)
+            .then(|| SimIoForGlobal::new(global).to_expr())
+    }
+    #[must_use]
+    pub fn expr_to_global(&self, expr: Expr<CanonicalType>) -> Option<FormalInput> {
+        let global = match *Expr::expr_enum(expr) {
+            ExprEnum::FormalInput(global) => global,
+            ExprEnum::SimIoForGlobal(expr) => expr.global(),
+            _ => return None,
+        };
+        self.global_io_map
+            .contains_key(&SimIoForGlobal::new(global))
+            .then_some(global)
+    }
+    #[must_use]
+    fn to_sim_io_target(&self, target: Interned<Target>) -> Interned<Target> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct FormalInputExprToSimIoExpr;
+        impl Memoize for FormalInputExprToSimIoExpr {
+            type Input = Interned<Target>;
+            type InputOwned = Interned<Target>;
+            type Output = Interned<Target>;
+
+            fn inner(self, input: &Self::Input) -> Self::Output {
+                match **input {
+                    Target::Base(base) => match *base {
+                        TargetBase::ModuleIO(_)
+                        | TargetBase::MemPort(_)
+                        | TargetBase::Reg(_)
+                        | TargetBase::RegSync(_)
+                        | TargetBase::RegAsync(_)
+                        | TargetBase::Wire(_)
+                        | TargetBase::Instance(_)
+                        | TargetBase::SimIoForGlobal(_) => *input,
+                        TargetBase::FormalInput(global) => {
+                            Target::from(SimIoForGlobal::new(global)).intern()
+                        }
+                    },
+                    Target::Child(child) => Target::Child(TargetChild::new(
+                        self.get_owned(child.parent()),
+                        child.path_element(),
+                    ))
+                    .intern_sized(),
+                }
+            }
+        }
+        match *target.base() {
+            TargetBase::ModuleIO(_)
+            | TargetBase::MemPort(_)
+            | TargetBase::Reg(_)
+            | TargetBase::RegSync(_)
+            | TargetBase::RegAsync(_)
+            | TargetBase::Wire(_)
+            | TargetBase::Instance(_)
+            | TargetBase::SimIoForGlobal(_) => target,
+            TargetBase::FormalInput(global) => {
+                if self.contains(global) {
+                    FormalInputExprToSimIoExpr.get_owned(target)
+                } else {
+                    target
+                }
+            }
+        }
+    }
+}
+
+impl IntoIterator for SimulationGlobalIo {
+    type Item = (FormalInput, Expr<CanonicalType>);
+    type IntoIter = SimulationGlobalIoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl IntoIterator for &'_ SimulationGlobalIo {
+    type Item = (FormalInput, Expr<CanonicalType>);
+    type IntoIter = SimulationGlobalIoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl IntoIterator for &'_ mut SimulationGlobalIo {
+    type Item = (FormalInput, Expr<CanonicalType>);
+    type IntoIter = SimulationGlobalIoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+macro_rules! make_simulation_global_io_iter {
+    (
+        impl $SimulationGlobalIoIter:ident {
+            fn $global_io_to_item:ident(
+                $global_io_to_item_arg:ident: (SimIoForGlobal, CompiledValue<CanonicalType>),
+            ) -> $item_ty:ty
+            $global_io_to_item_block:block
+        }
+    ) => {
+        #[derive(Clone, Default)]
+        pub struct $SimulationGlobalIoIter {
+            global_io: InternedSliceIter<(SimIoForGlobal, CompiledValue<CanonicalType>)>,
+        }
+
+        impl $SimulationGlobalIoIter {
+            fn $global_io_to_item(
+                $global_io_to_item_arg: (SimIoForGlobal, CompiledValue<CanonicalType>),
+            ) -> $item_ty
+            $global_io_to_item_block
+        }
+
+        impl Iterator for $SimulationGlobalIoIter {
+            type Item = $item_ty;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                self.global_io.next().map(Self::global_io_to_item)
+            }
+
+            fn size_hint(&self) -> (usize, Option<usize>) {
+                self.global_io.size_hint()
+            }
+
+            fn count(self) -> usize {
+                self.global_io.count()
+            }
+
+            fn last(mut self) -> Option<Self::Item> {
+                self.next_back()
+            }
+
+            fn nth(&mut self, n: usize) -> Option<Self::Item> {
+                self.global_io.nth(n).map(Self::global_io_to_item)
+            }
+
+            fn fold<B, F>(self, init: B, f: F) -> B
+            where
+                F: FnMut(B, Self::Item) -> B,
+            {
+                self.global_io.map(Self::global_io_to_item).fold(init, f)
+            }
+        }
+
+        impl std::iter::FusedIterator for $SimulationGlobalIoIter {}
+
+        impl DoubleEndedIterator for $SimulationGlobalIoIter {
+            fn next_back(&mut self) -> Option<Self::Item> {
+                self.global_io.next_back().map(Self::global_io_to_item)
+            }
+
+            fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+                self.global_io.nth_back(n).map(Self::global_io_to_item)
+            }
+
+            fn rfold<B, F>(self, init: B, f: F) -> B
+            where
+                F: FnMut(B, Self::Item) -> B,
+            {
+                self.global_io.map(Self::global_io_to_item).rfold(init, f)
+            }
+        }
+
+        impl ExactSizeIterator for $SimulationGlobalIoIter {}
+    };
+}
+
+make_simulation_global_io_iter! {
+    impl SimulationGlobalIoIter {
+        fn global_io_to_item(
+            v: (SimIoForGlobal, CompiledValue<CanonicalType>),
+        ) -> (FormalInput, Expr<CanonicalType>) {
+            let (global, _) = v;
+            (global.global(), global.to_expr())
+        }
+    }
+}
+
+impl SimulationGlobalIoIter {
+    #[must_use]
+    pub fn globals(self) -> SimulationGlobalIoGlobalsIter {
+        SimulationGlobalIoGlobalsIter {
+            global_io: self.global_io,
+        }
+    }
+    #[must_use]
+    pub fn exprs(self) -> SimulationGlobalIoExprsIter {
+        SimulationGlobalIoExprsIter {
+            global_io: self.global_io,
+        }
+    }
+}
+
+impl fmt::Debug for SimulationGlobalIoIter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("SimulationGlobalIoIter")
+            .field(&fmt::from_fn(|f| {
+                f.debug_map().entries(self.clone()).finish()
+            }))
+            .finish()
+    }
+}
+
+make_simulation_global_io_iter! {
+    impl SimulationGlobalIoGlobalsIter {
+        fn global_io_to_item(
+            v: (SimIoForGlobal, CompiledValue<CanonicalType>),
+        ) -> FormalInput {
+            let (global, _) = v;
+            global.global()
+        }
+    }
+}
+
+impl fmt::Debug for SimulationGlobalIoGlobalsIter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("SimulationGlobalIoGlobalsIter")
+            .field(&fmt::from_fn(|f| {
+                f.debug_set().entries(self.clone()).finish()
+            }))
+            .finish()
+    }
+}
+
+make_simulation_global_io_iter! {
+    impl SimulationGlobalIoExprsIter {
+        fn global_io_to_item(
+            v: (SimIoForGlobal, CompiledValue<CanonicalType>),
+        ) -> Expr<CanonicalType> {
+            let (global, _) = v;
+            global.to_expr()
+        }
+    }
+}
+
+impl fmt::Debug for SimulationGlobalIoExprsIter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("SimulationGlobalIoExprsIter")
+            .field(&fmt::from_fn(|f| {
+                f.debug_set().entries(self.clone()).finish()
+            }))
+            .finish()
+    }
+}
+
 pub struct Simulation<T: BundleType> {
     sim_impl: Rc<RefCell<SimulationImpl>>,
     io: Expr<T>,
@@ -3444,14 +3851,15 @@ macro_rules! impl_simulation_methods {
     (
         async_await = ($($async:tt, $await:tt)?),
         track_caller = ($(#[$track_caller:tt])?),
-        which_module = |$self:ident| $which_module:expr,
+        which_module = |$self:ident, $global_io:ident| $which_module:expr,
     ) => {
         $(#[$track_caller])?
         pub $($async)? fn read_bool_or_int<I: BoolOrIntType>(&mut $self, io: Expr<I>) -> I::Value {
-            let retval = $self
+            let retval = $self.sim_impl.borrow_mut().read_bool_or_int(
-                .sim_impl
+                io,
-                .borrow_mut()
+                ReadTime::Current,
-                .read_bool_or_int(io, ReadTime::Current, $which_module);
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
             $self.settle_if_needed(retval)$(.$await)?
         }
         $(#[$track_caller])?
@@ -3464,64 +3872,74 @@ macro_rules! impl_simulation_methods {
             $self.sim_impl.borrow_mut().write_bool_or_int(
                 io,
                 SimValue::into_value(value),
-                $which_module,
+                |$global_io: &SimulationGlobalIo| $which_module,
             );
         }
         $(#[$track_caller])?
         pub $($async)? fn write_clock(&mut $self, io: Expr<Clock>, value: bool) {
-            $self.sim_impl
+            $self.sim_impl.borrow_mut().write_bit(
-                .borrow_mut()
+                Expr::canonical(io),
-                .write_bit(Expr::canonical(io), value, $which_module);
+                value,
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
         }
         $(#[$track_caller])?
         pub $($async)? fn read_clock(&mut $self, io: Expr<Clock>) -> bool {
-            let retval = $self
+            let retval = $self.sim_impl.borrow_mut().read_bit(
-                .sim_impl
+                Expr::canonical(io),
-                .borrow_mut()
+                ReadTime::Current,
-                .read_bit(Expr::canonical(io), ReadTime::Current, $which_module);
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
             $self.settle_if_needed(retval)$(.$await)?
         }
         $(#[$track_caller])?
         pub $($async)? fn write_bool(&mut $self, io: Expr<Bool>, value: bool) {
-            $self.sim_impl
+            $self.sim_impl.borrow_mut().write_bit(
-                .borrow_mut()
+                Expr::canonical(io),
-                .write_bit(Expr::canonical(io), value, $which_module);
+                value,
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
         }
         $(#[$track_caller])?
         pub $($async)? fn read_bool(&mut $self, io: Expr<Bool>) -> bool {
-            let retval = $self
+            let retval = $self.sim_impl.borrow_mut().read_bit(
-                .sim_impl
+                Expr::canonical(io),
-                .borrow_mut()
+                ReadTime::Current,
-                .read_bit(Expr::canonical(io), ReadTime::Current, $which_module);
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
             $self.settle_if_needed(retval)$(.$await)?
         }
         $(#[$track_caller])?
         pub $($async)? fn write_reset<R: ResetType>(&mut $self, io: Expr<R>, value: bool) {
-            $self.sim_impl
+            $self.sim_impl.borrow_mut().write_bit(
-                .borrow_mut()
+                Expr::canonical(io),
-                .write_bit(Expr::canonical(io), value, $which_module);
+                value,
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
         }
         $(#[$track_caller])?
         pub $($async)? fn read_reset<R: ResetType>(&mut $self, io: Expr<R>) -> bool {
-            let retval = $self
+            let retval = $self.sim_impl.borrow_mut().read_bit(
-                .sim_impl
+                Expr::canonical(io),
-                .borrow_mut()
+                ReadTime::Current,
-                .read_bit(Expr::canonical(io), ReadTime::Current, $which_module);
+                |$global_io: &SimulationGlobalIo| $which_module,
+            );
             $self.settle_if_needed(retval)$(.$await)?
         }
         #[track_caller]
         pub fn is_reset_async<R: ResetType>(&$self, io: Expr<R>) -> bool {
-            $self
+            $self.sim_impl.borrow().is_reset_async(
-                .sim_impl
+                Expr::canonical(io),
-                .borrow_mut()
+                |$global_io: &SimulationGlobalIo| $which_module,
-                .is_reset_async(Expr::canonical(io), $which_module)
+            )
         }
         $(#[$track_caller])?
         pub $($async)? fn read<IO: Type>(&mut $self, io: Expr<IO>) -> SimValue<IO> {
-            let retval = $self
+            let retval = $self.sim_impl.borrow_mut().read(
-                .sim_impl
+                Expr::canonical(io),
-                .borrow_mut()
+                ReadTime::Current,
-                .read(Expr::canonical(io), ReadTime::Current, $which_module).1;
+                |$global_io: &SimulationGlobalIo| $which_module,
+            ).1;
             SimValue::from_canonical($self.settle_if_needed(retval)$(.$await)?)
         }
         $(#[$track_caller])?
@@ -3529,7 +3947,7 @@ macro_rules! impl_simulation_methods {
             $self.sim_impl.borrow_mut().write(
                 Expr::canonical(io),
                 &SimValue::into_canonical(value.into_sim_value_with_type(io.ty())),
-                $which_module,
+                |$global_io: &SimulationGlobalIo| $which_module,
             );
         }
     };
@@ -3568,6 +3986,9 @@ impl<T: BundleType> Simulation<T> {
     pub fn io(&self) -> Expr<T> {
         self.io.to_expr()
     }
+    pub fn global_io(&self) -> SimulationGlobalIo {
+        self.sim_impl.borrow().global_io.clone()
+    }
     pub fn from_compiled(compiled: Compiled<T>) -> Self {
         let sim_impl = SimulationImpl::new(compiled.canonical());
         Self {
@@ -3593,7 +4014,7 @@ impl<T: BundleType> Simulation<T> {
     impl_simulation_methods!(
         async_await = (),
         track_caller = (#[track_caller]),
-        which_module = |self| WhichModule::Main,
+        which_module = |self, global_io| WhichModule::Main { global_io },
     );
     #[doc(hidden)]
     /// This is explicitly unstable and may be changed/removed at any time
@@ -3662,7 +4083,7 @@ impl ExternModuleSimulationState {
             let (key, value) = self
                 .sim_impl
                 .borrow_mut()
-                .read(io, ReadTime::Current, which_module);
+                .read(io, ReadTime::Current, |_| which_module);
             let value = self.settle_if_needed(value).await;
             let key = Rc::new(key);
             if sensitivity_set.compiled_values.insert(key.clone()) {
@@ -3934,7 +4355,7 @@ impl ExternModuleSimulationState {
         let retval = self.sim_impl.borrow_mut().read_bool_or_int(
             io,
             ReadTime::Past { clock_for_past },
-            WhichModule::Extern {
+            |_| WhichModule::Extern {
                 module_index: self.module_index,
             },
         );
@@ -3950,7 +4371,7 @@ impl ExternModuleSimulationState {
         let retval = self.sim_impl.borrow_mut().read_bit(
             Expr::canonical(io),
             ReadTime::Past { clock_for_past },
-            WhichModule::Extern {
+            |_| WhichModule::Extern {
                 module_index: self.module_index,
             },
         );
@@ -3966,7 +4387,7 @@ impl ExternModuleSimulationState {
         let retval = self.sim_impl.borrow_mut().read_bit(
             Expr::canonical(io),
             ReadTime::Past { clock_for_past },
-            WhichModule::Extern {
+            |_| WhichModule::Extern {
                 module_index: self.module_index,
             },
         );
@@ -3986,7 +4407,7 @@ impl ExternModuleSimulationState {
         let retval = self.sim_impl.borrow_mut().read_bit(
             Expr::canonical(io),
             ReadTime::Past { clock_for_past },
-            WhichModule::Extern {
+            |_| WhichModule::Extern {
                 module_index: self.module_index,
             },
         );
@@ -4009,7 +4430,7 @@ impl ExternModuleSimulationState {
             .read(
                 Expr::canonical(io),
                 ReadTime::Past { clock_for_past },
-                WhichModule::Extern {
+                |_| WhichModule::Extern {
                     module_index: self.module_index,
                 },
             )
@@ -4019,7 +4440,7 @@ impl ExternModuleSimulationState {
     impl_simulation_methods!(
         async_await = (async, await),
         track_caller = (),
-        which_module = |self| WhichModule::Extern { module_index: self.module_index },
+        which_module = |self, _global_io| WhichModule::Extern { module_index: self.module_index },
     );
 }
 

crates/fayalite/src/sim/interpreter.rs

@@ -980,6 +980,7 @@ macro_rules! make_state {
             pub(crate) insns: Interned<Insns<InsnsBuildingDone>>,
             pub(crate) pc: usize,
             pub(crate) memory_write_log: Vec<(StatePartIndex<StatePartKindMemories>, usize)>,
+            pub(crate) assert_failed_log: Vec<usize>,
             $(pub(crate) $state_plural_field: StatePart<$state_kind>,)*
             $(pub(crate) $type_plural_field: StatePart<$type_kind>,)*
         }
@@ -990,6 +991,7 @@ macro_rules! make_state {
                     insns: _,
                     pc,
                     memory_write_log,
+                    assert_failed_log,
                     $($state_plural_field,)*
                     $($type_plural_field,)*
                 } = self;
@@ -997,6 +999,7 @@ macro_rules! make_state {
                     .field("insns", &InsnsOfState(self))
                     .field("pc", pc)
                     .field("memory_write_log", memory_write_log)
+                    .field("assert_failed_log", assert_failed_log)
                     $(.field(stringify!($state_plural_field), $state_plural_field))*
                     $(.field(stringify!($type_plural_field), $type_plural_field))*
                     .finish()
@@ -1009,6 +1012,7 @@ macro_rules! make_state {
                     insns,
                     pc: 0,
                     memory_write_log: Vec::with_capacity(32),
+                    assert_failed_log: Vec::new(),
                     $($state_plural_field: StatePart::new(&insns.state_layout.$state_plural_field.layout_data),)*
                     $($type_plural_field: StatePart::new(&insns.state_layout.ty.$type_plural_field.layout_data),)*
                 }
@@ -1020,6 +1024,7 @@ macro_rules! make_state {
                     pc: self.pc,
                     orig_pc: &mut self.pc,
                     memory_write_log: &mut self.memory_write_log,
+                    assert_failed_log: &mut self.assert_failed_log,
                     $($state_plural_field: self.$state_plural_field.borrow(),)*
                     $($type_plural_field: self.$type_plural_field.borrow(),)*
                 }
@@ -1042,6 +1047,7 @@ macro_rules! make_state {
             pub(crate) orig_pc: &'a mut usize,
             pub(crate) pc: usize,
             pub(crate) memory_write_log: &'a mut Vec<(StatePartIndex<StatePartKindMemories>, usize)>,
+            pub(crate) assert_failed_log: &'a mut Vec<usize>,
             $(pub(crate) $state_plural_field: BorrowedStatePart<'a, $state_kind>,)*
             $(pub(crate) $type_plural_field: BorrowedStatePart<'a, $type_kind>,)*
         }
@@ -1299,6 +1305,7 @@ impl State {
             insns: _,
             pc,
             memory_write_log: _,
+            assert_failed_log: _,
             memories: _,
             small_slots: _,
             big_slots: _,
@@ -1338,6 +1345,10 @@ impl BorrowedState<'_> {
             self.memory_write_log.push(log_entry);
         }
     }
+    #[cold]
+    fn assert_failed(&mut self, assert_index: usize) {
+        self.assert_failed_log.push(assert_index);
+    }
 }
 
 fn bigint_pow2(width: usize) -> Interned<BigInt> {
@@ -2105,6 +2116,19 @@ impl_insns! {
         state.log_memory_write(memory, addr);
         next!();
     }
+    Assert {
+        #[kind = Input]
+        clk_triggered: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Input]
+        pred: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Immediate]
+        assert_index: usize,
+    } => {
+        if state.small_slots[clk_triggered] != 0 && state.small_slots[pred] == 0 {
+            state.assert_failed(assert_index);
+        }
+        next!();
+    }
     Return => {
         break RunResult::Return(());
     }

crates/fayalite/src/sim/value.rs

@@ -1508,6 +1508,8 @@ impl<T: SimOnlyValueTrait> ToSimValue for SimOnlyValue<T> {
 }
 
 impl HdlPartialEqImpl<Self> for DynSimOnly {
+    const TRY_STRUCTURAL_EQ: bool = false;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,
@@ -1527,6 +1529,8 @@ impl HdlPartialEqImpl<Self> for DynSimOnly {
 impl<L: SimOnlyValueTrait + PartialEq<R>, R: SimOnlyValueTrait> HdlPartialEqImpl<SimOnly<R>>
     for SimOnly<L>
 {
+    const TRY_STRUCTURAL_EQ: bool = false;
+
     #[track_caller]
     fn cmp_value_eq(
         _lhs: Self,

crates/fayalite/src/sim/vcd.rs

@@ -9,11 +9,11 @@ use crate::{
     prelude::PhantomConst,
     sim::{
         TraceArray, TraceAsyncReset, TraceBool, TraceBundle, TraceClock, TraceDecl,
-        TraceEnumDiscriminant, TraceEnumWithFields, TraceFieldlessEnum, TraceInstance,
+        TraceEnumDiscriminant, TraceEnumWithFields, TraceFieldlessEnum, TraceFormalInput,
-        TraceLocation, TraceMem, TraceMemPort, TraceMemoryId, TraceMemoryLocation, TraceModule,
+        TraceInstance, TraceLocation, TraceMem, TraceMemPort, TraceMemoryId, TraceMemoryLocation,
-        TraceModuleIO, TracePhantomConst, TraceReg, TraceSInt, TraceScalar, TraceScalarId,
+        TraceModule, TraceModuleIO, TracePhantomConst, TraceReg, TraceSInt, TraceScalar,
-        TraceScope, TraceSimOnly, TraceSyncReset, TraceTraceAsString, TraceUInt, TraceWire,
+        TraceScalarId, TraceScope, TraceSimOnly, TraceSyncReset, TraceTraceAsString, TraceUInt,
-        TraceWriter, TraceWriterDecls,
+        TraceWire, TraceWriter, TraceWriterDecls,
         time::{SimDuration, SimInstant},
         value::DynSimOnlyValue,
     },
@@ -766,6 +766,7 @@ impl WriteTrace for TraceScope {
             Self::Wire(v) => v.write_trace(writer, arg),
             Self::Reg(v) => v.write_trace(writer, arg),
             Self::ModuleIO(v) => v.write_trace(writer, arg),
+            Self::FormalInput(v) => v.write_trace(writer, arg),
             Self::Bundle(v) => v.write_trace(writer, arg),
             Self::Array(v) => v.write_trace(writer, arg),
             Self::EnumWithFields(v) => v.write_trace(writer, arg),
@@ -963,6 +964,27 @@ impl WriteTrace for TraceModuleIO {
     }
 }
 
+impl WriteTrace for TraceFormalInput {
+    fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
+        let ArgModuleBody { properties, scope } = arg.module_body();
+        let Self {
+            name: _,
+            child,
+            formal_input: _,
+        } = self;
+        child.write_trace(
+            writer,
+            ArgInType {
+                source_var_type: "wire",
+                sink_var_type: "wire",
+                duplex_var_type: "wire",
+                properties,
+                scope: Some(scope),
+            },
+        )
+    }
+}
+
 impl WriteTrace for TraceBundle {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
         let ArgInType {

crates/fayalite/src/testing.rs

@@ -12,11 +12,13 @@ use crate::{
     bundle::BundleType,
     firrtl::ExportOptions,
     module::Module,
-    util::HashMap,
+    sim::{Simulation, vcd::VcdWriterDecls},
+    util::{HashMap, RcWriter},
 };
 use serde::{Deserialize, Serialize};
 use std::{
     fmt::{self, Write},
+    panic::Location,
     path::{Path, PathBuf},
     process::Command,
     sync::{Mutex, OnceLock},
@@ -222,3 +224,190 @@ pub fn assert_formal<M: AsRef<Module<T>>, T: BundleType>(
     )
     .expect("testing::assert_formal() failed");
 }
+
+pub struct CheckedVcdOutput {
+    writer: Option<RcWriter>,
+    expected_path: PathBuf,
+    expected_contents: Result<String, (Option<PathBuf>, std::io::Error)>,
+    location: &'static Location<'static>,
+}
+
+impl CheckedVcdOutput {
+    #[must_use]
+    #[track_caller]
+    pub fn new<T: BundleType>(sim: &mut Simulation<T>, expected_path: PathBuf) -> Self {
+        let writer = RcWriter::default();
+        sim.add_trace_writer(VcdWriterDecls::new(writer.clone()));
+        Self {
+            writer: Some(writer),
+            expected_contents: std::fs::read_to_string(&expected_path).map_err(|e| {
+                eprintln!(
+                    "error: failed to read expected VCD from: {}",
+                    expected_path.display(),
+                );
+                (std::env::current_dir().ok(), e)
+            }),
+            expected_path,
+            location: Location::caller(),
+        }
+    }
+    #[must_use]
+    #[track_caller]
+    #[doc(hidden)]
+    pub fn __checked_vcd_output_macro_helper<T: BundleType>(
+        sim: &mut Simulation<T>,
+        cargo_manifest_dir: &'static str,
+        path: &'static str,
+    ) -> Self {
+        Self::new(sim, Path::new(cargo_manifest_dir).join(path))
+    }
+    pub fn with_vcd_output<R>(&self, f: impl FnOnce(&str) -> R) -> R {
+        let Some(writer) = &self.writer else {
+            unreachable!();
+        };
+        writer.clone().borrow(|output| {
+            let Ok(output) = str::from_utf8(output) else {
+                unreachable!("VcdWriter writes valid UTF-8");
+            };
+            f(output)
+        })
+    }
+    #[track_caller]
+    pub fn finish(mut self) {
+        let Ok(()) = self.finish_impl(|msg| panic!("{msg}"));
+    }
+    fn finish_impl<E>(
+        &mut self,
+        error: impl FnOnce(std::fmt::Arguments<'_>) -> E,
+    ) -> Result<(), E> {
+        let Self {
+            writer: Some(writer),
+            expected_path,
+            expected_contents,
+            location,
+        } = self
+        else {
+            // already finished
+            return Ok(());
+        };
+        let Ok(vcd) = String::from_utf8(writer.take()) else {
+            unreachable!("VcdWriter writes valid UTF-8");
+        };
+        let expected_path_d = expected_path.display();
+        if expected_contents
+            .as_ref()
+            .is_ok_and(|expected_contents| *expected_contents == vcd)
+        {
+            // avoid written output from being split from threads interleaving writes to stdout
+            let _stdout = std::io::stderr().lock();
+            // use println to get output captured by tests
+            println!("\n{location}: generated VCD matches the expected VCD in {expected_path_d}");
+            return Ok(());
+        }
+        // avoid written output from being split from threads interleaving writes to stderr
+        let _stderr = std::io::stderr().lock();
+        let error = |msg: std::fmt::Arguments<'_>| {
+            // print msg at both beginning and end so it's easier to find when the vcd is huge
+            Err(error(format_args!(
+                "\n{msg}####### VCD:\n{vcd}\n#######\n{msg}"
+            )))
+        };
+        let error = |msg: std::fmt::Arguments<'_>| match &*expected_contents {
+            Ok(_) => error(format_args!(
+                "{location}: generated VCD doesn't match the expected VCD in {expected_path_d}\n\
+                {msg}",
+            )),
+            Err((Some(current_dir), e)) => error(format_args!(
+                "{location}: generated VCD doesn't match the expected VCD in {expected_path_d}\n\
+                error: failed to read: {e}\n\
+                current dir: {current_dir}\n\
+                {msg}",
+                current_dir = current_dir.display(),
+            )),
+            Err((None, e)) => error(format_args!(
+                "{location}: generated VCD doesn't match the expected VCD in {expected_path_d}\n\
+                error: failed to read: {e}\n\
+                {msg}",
+            )),
+        };
+        const OVERWRITE_VAR_NAME: &str = "OVERWRITE_EXPECTED_VCD";
+        const OVERWRITE_VAR_VALUE: &str = "overwrite";
+        match std::env::var_os(OVERWRITE_VAR_NAME) {
+            Some(v) if v == OVERWRITE_VAR_VALUE => match std::fs::write(&expected_path, &vcd) {
+                Ok(()) => error(format_args!(
+                    "warning: since `{OVERWRITE_VAR_NAME}={OVERWRITE_VAR_VALUE}` is set -- writing the generated VCD to {expected_path_d}\n"
+                )),
+                Err(e) => error(format_args!(
+                    "error: since `{OVERWRITE_VAR_NAME}={OVERWRITE_VAR_VALUE}` is set -- tried to write the generated VCD to {expected_path_d}\n\
+                    error: failed to write: {e}"
+                )),
+            },
+            _ => error(format_args!(
+                "note: rerun the test with the environment variable `{OVERWRITE_VAR_NAME}={OVERWRITE_VAR_VALUE}`\n\
+                to update the expected output to match the generated output.\n"
+            )),
+        }
+    }
+}
+
+impl Drop for CheckedVcdOutput {
+    #[track_caller]
+    fn drop(&mut self) {
+        let _ = self.finish_impl(|msg| {
+            if std::thread::panicking() {
+                eprintln!("{msg}"); // use eprintln to get output captured by tests
+            } else {
+                panic!("{msg}");
+            }
+        });
+    }
+}
+
+#[macro_export]
+/// Use in tests to check that [`Simulation`] generates the expected VCD traces, by comparing to a `.vcd` file containing the expected traces.
+///
+/// Use like so:
+/// ```
+/// # use fayalite::prelude::*;
+/// #
+/// # #[hdl_module]
+/// # fn my_module() {
+/// #     #[hdl]
+/// #     let a: UInt<8> = m.input();
+/// #     #[hdl]
+/// #     let b: UInt<8> = m.output();
+/// #     connect(b, 0u8);
+/// #     #[hdl]
+/// #     if a.cmp_eq(100u8) {
+/// #         connect(b, 42u8);
+/// #     }
+/// # }
+/// // inside your #[test] fn my_test():
+///
+/// // get the module to simulate:
+/// let m = my_module();
+/// // create a simulation of the module:
+/// let mut sim = Simulation::new(m);
+/// // set up the expected VCD traces, the given .vcd path is relative to env!("CARGO_MANIFEST_DIR")
+/// let _checked_vcd_output = checked_vcd_output!(
+///     &mut sim,
+///     "tests/expected/my_test.vcd",
+/// );
+/// // now run the simulation like normal:
+/// sim.write(sim.io().a, 0u8);
+/// assert_eq!(sim.read(sim.io().b).as_int(), 0);
+/// sim.advance_time(SimDuration::from_micros(1));
+/// sim.write(sim.io().a, 100u8);
+/// assert_eq!(sim.read(sim.io().b).as_int(), 42);
+/// ```
+macro_rules! checked_vcd_output {
+    ($sim:expr, $path_relative_to_manifest_dir:expr $(,)?) => {
+        $crate::testing::CheckedVcdOutput::__checked_vcd_output_macro_helper(
+            $sim,
+            $crate::__std::env!("CARGO_MANIFEST_DIR"),
+            $crate::__std::concat!($path_relative_to_manifest_dir),
+        )
+    };
+}
+
+pub use checked_vcd_output;

crates/fayalite/src/ty.rs

@@ -354,6 +354,39 @@ impl CanonicalType {
         }
         MyMemoize.get_owned((self, other))
     }
+    pub fn contains_sim_only(self) -> bool {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize;
+        impl Memoize for MyMemoize {
+            type Input = CanonicalType;
+            type InputOwned = CanonicalType;
+            type Output = bool;
+
+            fn inner(self, input: &Self::Input) -> Self::Output {
+                match input {
+                    CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_) => {
+                        false
+                    }
+                    CanonicalType::Array(ty) => ty.element().contains_sim_only(),
+                    CanonicalType::Enum(ty) => ty
+                        .variants()
+                        .iter()
+                        .any(|v| v.ty.is_some_and(CanonicalType::contains_sim_only)),
+                    CanonicalType::Bundle(ty) => {
+                        ty.fields().iter().any(|v| v.ty.contains_sim_only())
+                    }
+                    CanonicalType::AsyncReset(_)
+                    | CanonicalType::SyncReset(_)
+                    | CanonicalType::Reset(_)
+                    | CanonicalType::Clock(_)
+                    | CanonicalType::PhantomConst(_) => false,
+                    CanonicalType::DynSimOnly(_) => true,
+                    CanonicalType::TraceAsString(ty) => ty.inner_ty().contains_sim_only(),
+                }
+            }
+        }
+        MyMemoize.get_owned(self)
+    }
 }
 
 pub trait MatchVariantAndInactiveScope: Sized {
@@ -1309,16 +1342,49 @@ trait TraceAsStringTrait: fmt::Debug + 'static + Send + Sync + SupportsPtrEqWith
     fn can_substitute_type(&self, new_type: CanonicalType) -> bool;
 }
 
-impl<T: Type> TraceAsStringTrait for T {
+#[derive(Clone, PartialEq, Eq, Hash)]
+struct TraceAsStringState<T: Type> {
+    ty: Interned<T>,
+    canonical_ty: CanonicalType,
+}
+
+impl<T: Type> TraceAsStringState<T> {
+    fn new(ty: Interned<T>) -> Interned<Self> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize<T: Type>(PhantomData<T>);
+        impl<T: Type> Memoize for MyMemoize<T> {
+            type Input = Interned<T>;
+            type InputOwned = Interned<T>;
+            type Output = Interned<TraceAsStringState<T>>;
+
+            fn inner(self, input: &Self::Input) -> Self::Output {
+                TraceAsStringState {
+                    ty: *input,
+                    canonical_ty: input.canonical(),
+                }
+                .intern_sized()
+            }
+        }
+        MyMemoize(PhantomData).get_owned(ty)
+    }
+}
+
+impl<T: Type> fmt::Debug for TraceAsStringState<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.ty.fmt(f)
+    }
+}
+
+impl<T: Type> TraceAsStringTrait for TraceAsStringState<T> {
     fn trace_fmt(
         &self,
         opaque: OpaqueSimValueSlice<'_>,
         f: &mut fmt::Formatter<'_>,
     ) -> fmt::Result {
-        fmt::Debug::fmt(&Type::sim_value_from_opaque(self, opaque), f)
+        fmt::Debug::fmt(&Type::sim_value_from_opaque(&*self.ty, opaque), f)
     }
     fn can_substitute_type(&self, new_type: CanonicalType) -> bool {
-        self.canonical().is_layout_equivalent(new_type)
+        self.canonical_ty.is_layout_equivalent(new_type)
     }
 }
 
@@ -1374,7 +1440,7 @@ impl<T: Type> TraceAsString<T> {
         Self {
             inner_ty: LazyInterned::Interned(inner_ty),
             trace_as_string: LazyInterned::Interned(Interned::cast_unchecked(
-                inner_ty,
+                TraceAsStringState::new(inner_ty),
                 |v| -> &dyn TraceAsStringTrait { v },
             )),
         }
@@ -1548,7 +1614,10 @@ impl<T: StaticType> Default for TraceAsStringStaticTypeHelper<T> {
 
 impl<T: StaticType> From<TraceAsStringStaticTypeHelper<T>> for Interned<dyn TraceAsStringTrait> {
     fn from(_value: TraceAsStringStaticTypeHelper<T>) -> Self {
-        Interned::cast_unchecked(T::TYPE.intern_sized(), |v| -> &dyn TraceAsStringTrait { v })
+        Interned::cast_unchecked(
+            TraceAsStringState::new(T::TYPE.intern_sized()),
+            |v| -> &dyn TraceAsStringTrait { v },
+        )
     }
 }
 
@@ -1846,6 +1915,8 @@ fn trace_as_string_cow_into_inner_value<T: Type>(
 }
 
 impl<T: HdlPartialEqImpl<U>, U: Type> HdlPartialEqImpl<TraceAsString<U>> for TraceAsString<T> {
+    const TRY_STRUCTURAL_EQ: bool = <T as HdlPartialEqImpl<U>>::TRY_STRUCTURAL_EQ;
+
     #[track_caller]
     fn cmp_value_eq(
         lhs: Self,

crates/fayalite/src/util.rs

@@ -16,8 +16,8 @@ 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 HashMap<K, V, H = DefaultBuildHasher> = hashbrown::HashMap<K, V, H>;
-pub(crate) type HashSet<T> = hashbrown::HashSet<T, DefaultBuildHasher>;
+pub(crate) type HashSet<T, H = DefaultBuildHasher> = hashbrown::HashSet<T, H>;
 
 #[doc(inline)]
 pub use const_bool::{ConstBool, ConstBoolDispatch, ConstBoolDispatchTag, GenericConstBool};
@@ -43,7 +43,11 @@ pub use misc::{
 };
 pub(crate) use misc::{InternedStrCompareAsStr, chain, copy_le_bytes_to_bitslice};
 
+pub mod bool_fixed_point_solver;
+pub(crate) mod indented_print;
 pub mod job_server;
+pub mod map_trait;
 pub mod prefix_sum;
 pub mod ready_valid;
 pub(crate) mod serde_by_id;
+pub mod union_find_map;

crates/fayalite/src/util/bool_fixed_point_solver.rs

@@ -0,0 +1,711 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use petgraph::unionfind::UnionFind;
+use std::{collections::BTreeSet, fmt};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Variable(usize);
+
+impl Variable {
+    pub fn index(self) -> usize {
+        self.0
+    }
+}
+
+impl fmt::Debug for Variable {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Variable {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "v{}", self.0)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum Constraint {
+    /// `variable` is constrained to be [`!solver.unconstrained_variables_value()`](BoolFixedPointSolver::unconstrained_variables_value())
+    MaximallyConstrained { variable: Variable },
+    /// the constraint is `dest == src`
+    Equal { dest: Variable, src: Variable },
+    /// the constraint is `dest == dest & src`
+    And { dest: Variable, src: Variable },
+    /// the constraint is `dest == dest | src`
+    Or { dest: Variable, src: Variable },
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+/// the constraint is `dest == dest & src`
+struct AndConstraint {
+    dest: Variable,
+    src: Variable,
+}
+
+impl AndConstraint {
+    fn from_or_constraint(or_constraint_dest: Variable, or_constraint_src: Variable) -> Self {
+        // `a == a | b` is equivalent to `b == b & a`
+        Self {
+            dest: or_constraint_src,
+            src: or_constraint_dest,
+        }
+    }
+}
+
+impl fmt::Debug for AndConstraint {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self { dest, src } = *self;
+        write!(f, "{dest} == {dest} & {src}")
+    }
+}
+
+#[derive(Clone)]
+pub struct BoolFixedPointSolver {
+    variables_union_find: UnionFind<usize>,
+    variables_value: Vec<bool>,
+    maximally_constrained: Vec<bool>,
+    unconstrained_variables_value: bool,
+    solved: bool,
+    and_constraints: BTreeSet<AndConstraint>,
+}
+
+impl fmt::Debug for BoolFixedPointSolver {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self {
+            variables_union_find,
+            variables_value,
+            maximally_constrained,
+            unconstrained_variables_value,
+            solved,
+            and_constraints,
+        } = self;
+        f.debug_struct("BoolFixedPointSolver")
+            .field(
+                "variables_union_find",
+                &fmt::from_fn(|f| {
+                    f.debug_map()
+                        .entries(
+                            (0..variables_union_find.len())
+                                .map(|i| (Variable(i), Variable(variables_union_find.find(i)))),
+                        )
+                        .finish()
+                }),
+            )
+            .field(
+                "variables_value",
+                &fmt::from_fn(|f| {
+                    let mut debug_map = f.debug_map();
+                    for (i, v) in variables_value.iter().enumerate() {
+                        if variables_union_find.find(i) == i {
+                            debug_map.entry(&Variable(i), v);
+                        }
+                    }
+                    debug_map.finish()
+                }),
+            )
+            .field(
+                "maximally_constrained",
+                &fmt::from_fn(|f| {
+                    let mut debug_map = f.debug_map();
+                    for (i, v) in maximally_constrained.iter().enumerate() {
+                        if variables_union_find.find(i) == i {
+                            debug_map.entry(&Variable(i), v);
+                        }
+                    }
+                    debug_map.finish()
+                }),
+            )
+            .field(
+                "unconstrained_variables_value",
+                unconstrained_variables_value,
+            )
+            .field("solved", solved)
+            .field("and_constraints", and_constraints)
+            .finish()
+    }
+}
+
+impl BoolFixedPointSolver {
+    pub const fn new(unconstrained_variables_value: bool) -> Self {
+        Self {
+            variables_union_find: UnionFind::new_empty(),
+            variables_value: Vec::new(),
+            maximally_constrained: Vec::new(),
+            unconstrained_variables_value,
+            solved: false,
+            and_constraints: BTreeSet::new(),
+        }
+    }
+    pub fn unconstrained_variables_value(&self) -> bool {
+        self.unconstrained_variables_value
+    }
+    pub fn new_variable(&mut self) -> Variable {
+        let index = self.variables_union_find.new_set();
+        self.variables_value
+            .push(self.unconstrained_variables_value);
+        self.maximally_constrained.push(false);
+        self.solved = false;
+        Variable(index)
+    }
+    pub fn variable_count(&self) -> usize {
+        self.variables_union_find.len()
+    }
+    #[track_caller]
+    fn assert_variable_in_range(&self, variable: Variable) {
+        if variable.0 >= self.variable_count() {
+            panic!("invalid variable {variable:?}");
+        }
+    }
+    #[track_caller]
+    pub fn add_constraint(&mut self, constraint: Constraint) {
+        self.solved = false;
+        match constraint {
+            Constraint::MaximallyConstrained { variable } => {
+                self.assert_variable_in_range(variable);
+                self.maximally_constrained[self.variables_union_find.find_mut(variable.0)] = true;
+                return;
+            }
+            Constraint::Equal { dest, src } => {
+                self.assert_variable_in_range(dest);
+                self.assert_variable_in_range(src);
+                let maximally_constrained = self.maximally_constrained
+                    [self.variables_union_find.find_mut(dest.0)]
+                    | self.maximally_constrained[self.variables_union_find.find_mut(src.0)];
+                self.variables_union_find.union(dest.0, src.0);
+                let merged_index = self.variables_union_find.find_mut(dest.0);
+                self.maximally_constrained[merged_index] = maximally_constrained;
+            }
+            Constraint::And { dest, src } => {
+                self.assert_variable_in_range(src);
+                self.assert_variable_in_range(dest);
+                if src != dest {
+                    self.and_constraints.insert(AndConstraint { dest, src });
+                }
+            }
+            Constraint::Or { dest, src } => {
+                self.assert_variable_in_range(src);
+                self.assert_variable_in_range(dest);
+                if src != dest {
+                    self.and_constraints
+                        .insert(AndConstraint::from_or_constraint(dest, src));
+                }
+            }
+        }
+    }
+    pub fn solve(&mut self) {
+        for (value, maximally_constrained) in self
+            .variables_value
+            .iter_mut()
+            .zip(&self.maximally_constrained)
+        {
+            *value = self.unconstrained_variables_value ^ *maximally_constrained;
+        }
+        let mut variables_to_constraints_map: Vec<Vec<AndConstraint>> =
+            vec![Vec::new(); self.variable_count()];
+        for &AndConstraint { mut dest, mut src } in &self.and_constraints {
+            dest.0 = self.variables_union_find.find_mut(dest.0);
+            src.0 = self.variables_union_find.find_mut(src.0);
+            if dest == src {
+                continue;
+            }
+            let constraint = AndConstraint { dest, src };
+            variables_to_constraints_map[dest.0].push(constraint);
+            variables_to_constraints_map[src.0].push(constraint);
+        }
+        let mut worklist: Vec<Variable> = (0..self.variable_count())
+            .filter(|&index| self.variables_union_find.find_mut(index) == index)
+            .map(Variable)
+            .collect();
+        while let Some(variable) = worklist.pop() {
+            for &AndConstraint { dest, src } in &variables_to_constraints_map[variable.0] {
+                let dest_value = self.variables_value[dest.0];
+                let src_value = self.variables_value[src.0];
+                // equivalent to `dest_value != dest_value & src_value`:
+                let is_unsatisfied = dest_value && !src_value;
+                if is_unsatisfied {
+                    if self.unconstrained_variables_value {
+                        self.variables_value[dest.0] = false;
+                        worklist.push(dest);
+                    } else {
+                        self.variables_value[src.0] = true;
+                        worklist.push(src);
+                    }
+                }
+            }
+        }
+        self.solved = true;
+    }
+    #[track_caller]
+    pub fn value(&mut self, variable: Variable) -> bool {
+        #[cold]
+        fn solve_cold(this: &mut BoolFixedPointSolver) {
+            this.solve();
+        }
+        self.assert_variable_in_range(variable);
+        if !self.solved {
+            solve_cold(self);
+        }
+        self.variables_value[self.variables_union_find.find_mut(variable.0)]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::num::NonZero;
+
+    struct TestCase<'a, C, Vars, Vals> {
+        variable_count: usize,
+        expected_values: Option<&'a [bool]>,
+        constraints: C,
+        variables: Vars,
+        values: Vals,
+        solver: BoolFixedPointSolver,
+    }
+
+    impl<'a, C: FnOnce(&[Variable]) -> I, I: IntoIterator<Item = Constraint>> TestCase<'a, C, (), ()> {
+        fn new_expected(
+            unconstrained_variables_value: bool,
+            expected_values: &'a [bool],
+            constraints: C,
+        ) -> Self {
+            Self {
+                variable_count: expected_values.len(),
+                expected_values: Some(expected_values),
+                constraints,
+                variables: (),
+                values: (),
+                solver: BoolFixedPointSolver::new(unconstrained_variables_value),
+            }
+        }
+        #[track_caller]
+        fn get_constraints_and_variables(
+            self,
+        ) -> TestCase<'a, Vec<Constraint>, Vec<Variable>, [bool; 0]> {
+            let Self {
+                variable_count,
+                expected_values,
+                constraints,
+                variables: (),
+                values: (),
+                mut solver,
+            } = self;
+            assert_eq!(
+                expected_values.map_or(variable_count, |v| v.len()),
+                variable_count,
+            );
+            let variables = Vec::from_iter((0..variable_count).map(|_| solver.new_variable()));
+            let constraints = Vec::from_iter(constraints(&variables));
+            TestCase {
+                variable_count,
+                expected_values,
+                constraints,
+                variables,
+                values: [],
+                solver,
+            }
+        }
+    }
+
+    impl<'a> TestCase<'a, Vec<Constraint>, Vec<Variable>, [bool; 0]> {
+        #[track_caller]
+        fn add_and_check_constraints(&mut self) {
+            if let Some(expected_values) = self.expected_values {
+                self.check_constraints("expected values", expected_values);
+            }
+            for &constraint in &self.constraints {
+                self.solver.add_constraint(constraint);
+            }
+        }
+        #[track_caller]
+        fn get_values(self) -> TestCase<'a, Vec<Constraint>, Vec<Variable>, Vec<bool>> {
+            let Self {
+                variable_count,
+                expected_values,
+                constraints,
+                variables,
+                values: [],
+                mut solver,
+            } = self;
+            let values = Vec::from_iter(variables.iter().map(|&v| solver.value(v)));
+            TestCase {
+                variable_count,
+                expected_values,
+                constraints,
+                variables,
+                values,
+                solver,
+            }
+        }
+    }
+
+    impl<'a> TestCase<'a, Vec<Constraint>, Vec<Variable>, Vec<bool>> {
+        #[track_caller]
+        fn check_values(&self) {
+            let Self {
+                variable_count: _,
+                expected_values,
+                constraints: _,
+                variables,
+                values,
+                solver: _,
+            } = self;
+            if let Some(expected_values) = expected_values {
+                for ((&expected_value, &variable), &value) in
+                    expected_values.iter().zip(variables).zip(values)
+                {
+                    if expected_value != value {
+                        self.error(format_args!(
+                            "solver output for {variable} of {value:?} doesn't \
+                            match expected value of {expected_value:?}",
+                        ));
+                    }
+                }
+            }
+            self.check_constraints("solved values", values);
+        }
+    }
+
+    impl<'a, Vals: AsRef<[bool]>> TestCase<'a, Vec<Constraint>, Vec<Variable>, Vals> {
+        #[track_caller]
+        fn check_constraints(&self, values_name: &str, values: &[bool]) {
+            let unconstrained_variables_value = self.solver.unconstrained_variables_value();
+            let v = |variable: Variable| values[variable.index()];
+            for &constraint in &self.constraints {
+                let satisfied = match constraint {
+                    Constraint::MaximallyConstrained { variable } => {
+                        v(variable) != unconstrained_variables_value
+                    }
+                    Constraint::Equal { dest, src } => v(dest) == v(src),
+                    Constraint::And { dest, src } => v(dest) == v(dest) & v(src),
+                    Constraint::Or { dest, src } => v(dest) == v(dest) | v(src),
+                };
+                if !satisfied {
+                    self.error(format_args!(
+                        "{values_name} don't satisfy constraint: {constraint:#?}"
+                    ));
+                }
+            }
+        }
+        #[track_caller]
+        fn error(&self, msg: fmt::Arguments<'_>) -> ! {
+            let Self {
+                variable_count,
+                expected_values,
+                ref constraints,
+                ref variables,
+                ref values,
+                ref solver,
+            } = *self;
+            let values = values.as_ref();
+            panic!(
+                "{msg}\n\
+                values={values:#?}\n\
+                constraints={constraints:#?}\n\
+                solver={solver:#?}",
+                values = fmt::from_fn(|f| {
+                    let mut debug_map = f.debug_map();
+                    for i in 0..variable_count {
+                        debug_map.key(&variables[i]);
+                        if let Some(value) = values.get(i) {
+                            if let Some(expected_values) = expected_values {
+                                debug_map.value(&format_args!(
+                                    "{value:?} (expected: {:?})",
+                                    expected_values[i],
+                                ));
+                            } else {
+                                debug_map.value(value);
+                            }
+                        } else if let Some(expected_values) = expected_values {
+                            debug_map.value(&format_args!("(expected: {:?})", expected_values[i]));
+                        } else {
+                            debug_map.value(&format_args!("None"));
+                        }
+                    }
+                    debug_map.finish()
+                }),
+            );
+        }
+    }
+
+    #[track_caller]
+    fn test_case<I: IntoIterator<Item = Constraint>>(
+        test_case: TestCase<'_, impl FnOnce(&[Variable]) -> I, (), ()>,
+    ) {
+        let mut test_case = test_case.get_constraints_and_variables();
+        test_case.add_and_check_constraints();
+        let test_case = test_case.get_values();
+        test_case.check_values();
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_simple() {
+        test_case(TestCase::new_expected(false, &[], |_| []));
+        test_case(TestCase::new_expected(true, &[], |_| []));
+        test_case(TestCase::new_expected(false, &[false], |_| []));
+        test_case(TestCase::new_expected(true, &[true], |_| []));
+        test_case(TestCase::new_expected(false, &[true], |v| {
+            [Constraint::MaximallyConstrained { variable: v[0] }]
+        }));
+        test_case(TestCase::new_expected(true, &[false], |v| {
+            [Constraint::MaximallyConstrained { variable: v[0] }]
+        }));
+        test_case(TestCase::new_expected(false, &[true, true], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Equal {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(true, &[false, false], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Equal {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(false, &[true, false], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::And {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(true, &[false, false], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::And {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(false, &[true, true], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::And {
+                    dest: v[0],
+                    src: v[1],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(true, &[false, true], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::And {
+                    dest: v[0],
+                    src: v[1],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(false, &[true, true], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Or {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(true, &[false, true], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Or {
+                    dest: v[1],
+                    src: v[0],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(false, &[true, false], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Or {
+                    dest: v[0],
+                    src: v[1],
+                },
+            ]
+        }));
+        test_case(TestCase::new_expected(true, &[false, false], |v| {
+            [
+                Constraint::MaximallyConstrained { variable: v[0] },
+                Constraint::Or {
+                    dest: v[0],
+                    src: v[1],
+                },
+            ]
+        }));
+    }
+
+    #[derive(Debug)]
+    struct Rng {
+        state: u64,
+    }
+
+    impl Rng {
+        fn new(test_case_index: u32) -> Self {
+            Self {
+                state: (test_case_index as u64) << 32,
+            }
+        }
+        fn next_u64(&mut self) -> u64 {
+            self.state += 1;
+            // 4 random primes and 4 random rotate amounts
+            self.state
+                .wrapping_mul(0xA3C7_8807_EA6D_A4F9)
+                .rotate_left(43)
+                .wrapping_mul(0x1CCA_797A_6BF8_8C63)
+                .rotate_left(8)
+                .wrapping_mul(0xCC50_AA59_7C41_946F)
+                .rotate_left(12)
+                .wrapping_mul(0xFB2A_0137_F878_C4B5)
+                .rotate_left(58)
+        }
+        #[track_caller]
+        fn next_u64_in_range(&mut self, range: std::ops::Range<u64>) -> u64 {
+            let Some(len) = range.end.checked_sub(range.start).and_then(NonZero::new) else {
+                panic!("empty range: {range:?}");
+            };
+            let max_quotient = u64::MAX / len;
+            loop {
+                let next_u64 = self.next_u64();
+                let quotient = next_u64 / len;
+                let remainder = next_u64 % len;
+                if quotient < max_quotient {
+                    return remainder + range.start;
+                }
+            }
+        }
+        #[track_caller]
+        fn next_usize_in_range(&mut self, range: std::ops::Range<usize>) -> usize {
+            self.next_u64_in_range(range.start as u64..range.end as u64) as usize
+        }
+        #[track_caller]
+        fn next_from_slice<'a, T>(&mut self, slice: &'a [T]) -> &'a T {
+            assert!(!slice.is_empty());
+            &slice[self.next_usize_in_range(0..slice.len())]
+        }
+        fn next_bool(&mut self) -> bool {
+            (self.next_u64() & 1) != 0
+        }
+    }
+
+    #[track_caller]
+    fn test_bool_fixed_point_solver_random_case(test_case_index: u32) {
+        println!("test_bool_fixed_point_solver_random_case({test_case_index})");
+        let mut rng = Rng::new(test_case_index);
+        // bias towards smaller problems to make them easier to debug
+        let variable_count = rng
+            .next_u64_in_range(1..1_000_000)
+            .pow(2)
+            .div_ceil(1_000_000_000) as usize;
+        let constraint_count =
+            rng.next_usize_in_range(0..(variable_count * variable_count).clamp(0, 10000));
+        let solver = BoolFixedPointSolver::new(rng.next_bool());
+        test_case(TestCase {
+            variable_count,
+            expected_values: None,
+            constraints: |variables: &[Variable]| {
+                Vec::from_iter(
+                    (0..constraint_count).map(|_| match rng.next_usize_in_range(0..4) {
+                        0 => Constraint::MaximallyConstrained {
+                            variable: *rng.next_from_slice(variables),
+                        },
+                        1 => Constraint::Equal {
+                            dest: *rng.next_from_slice(variables),
+                            src: *rng.next_from_slice(variables),
+                        },
+                        2 => Constraint::And {
+                            dest: *rng.next_from_slice(variables),
+                            src: *rng.next_from_slice(variables),
+                        },
+                        3 => Constraint::Or {
+                            dest: *rng.next_from_slice(variables),
+                            src: *rng.next_from_slice(variables),
+                        },
+                        4.. => unreachable!(),
+                    }),
+                )
+            },
+            variables: (),
+            values: (),
+            solver,
+        });
+    }
+
+    const CASES_FULL_RANGE: std::ops::Range<u32> = 0..100_000;
+
+    fn mul_div(v: u32, factor: u32, divisor: u32) -> u32 {
+        ((v as u64 * factor as u64) / divisor as u64) as u32
+    }
+
+    #[track_caller]
+    fn test_bool_fixed_point_solver_random_cases(split_index: u32) {
+        assert!(split_index < CASES_SPLIT_COUNT);
+        let full_range_len = CASES_FULL_RANGE.end - CASES_FULL_RANGE.start;
+        let start = mul_div(split_index, full_range_len, CASES_SPLIT_COUNT);
+        let end = mul_div(split_index + 1, full_range_len, CASES_SPLIT_COUNT);
+        for test_case_index in start..end {
+            test_bool_fixed_point_solver_random_case(test_case_index)
+        }
+    }
+
+    const CASES_SPLIT_COUNT: u32 = 10;
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_0() {
+        test_bool_fixed_point_solver_random_cases(0);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_1() {
+        test_bool_fixed_point_solver_random_cases(1);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_2() {
+        test_bool_fixed_point_solver_random_cases(2);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_3() {
+        test_bool_fixed_point_solver_random_cases(3);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_4() {
+        test_bool_fixed_point_solver_random_cases(4);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_5() {
+        test_bool_fixed_point_solver_random_cases(5);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_6() {
+        test_bool_fixed_point_solver_random_cases(6);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_7() {
+        test_bool_fixed_point_solver_random_cases(7);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_8() {
+        test_bool_fixed_point_solver_random_cases(8);
+    }
+
+    #[test]
+    fn test_bool_fixed_point_solver_random_cases_9() {
+        test_bool_fixed_point_solver_random_cases(9);
+    }
+}

crates/fayalite/src/util/indented_print.rs

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use std::{
+    fmt::{self, Write as _},
+    marker::PhantomData,
+};
+
+struct IndentState {
+    indent: usize,
+    need_indent: bool,
+    buf: String,
+}
+
+thread_local! {
+    static INDENT_STATE: std::cell::RefCell<IndentState>  = const {
+        std::cell::RefCell::new(IndentState {
+            indent: 0,
+            need_indent: true,
+            buf: String::new(),
+        })
+    };
+}
+
+struct IndentedOut;
+
+impl fmt::Write for IndentedOut {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        INDENT_STATE.with_borrow_mut(|state| {
+            let IndentState {
+                indent,
+                need_indent,
+                buf,
+            } = state;
+            buf.clear();
+            for ch in s.chars() {
+                if ch == '\n' {
+                    *need_indent = true;
+                } else {
+                    if *need_indent {
+                        *need_indent = false;
+                        for _ in 0..*indent {
+                            buf.push_str("    ");
+                        }
+                    }
+                }
+                buf.push(ch)
+            }
+            std::print!("{buf}");
+        });
+        Ok(())
+    }
+}
+
+#[allow(unused)]
+pub(crate) struct PushIndent(PhantomData<*const ()>);
+
+impl Drop for PushIndent {
+    fn drop(&mut self) {
+        let _ = INDENT_STATE.try_with(|state| state.borrow_mut().indent -= 1);
+    }
+}
+
+impl PushIndent {
+    #[allow(unused)]
+    pub(crate) fn new() -> Self {
+        INDENT_STATE.with_borrow_mut(|state| state.indent += 1);
+        Self(PhantomData)
+    }
+}
+
+#[allow(unused)]
+pub(crate) fn indented_print_fmt<const LN: bool>(args: fmt::Arguments<'_>) {
+    if LN {
+        writeln!(IndentedOut, "{args}").expect("writing can't fail")
+    } else {
+        IndentedOut.write_fmt(args).expect("writing can't fail")
+    }
+}
+
+#[allow(unused)]
+macro_rules! indented_print {
+    ($($args:tt)*) => {
+        $crate::util::indented_print::indented_print_fmt::<false>($crate::__std::format_args!($($args)*))
+    };
+}
+
+#[allow(unused)]
+pub(crate) use indented_print;
+
+#[allow(unused)]
+macro_rules! indented_println {
+    ($($args:tt)*) => {
+        $crate::util::indented_print::indented_print_fmt::<true>($crate::__std::format_args!($($args)*))
+    };
+}
+
+#[allow(unused)]
+pub(crate) use indented_println;
+
+#[allow(unused)]
+macro_rules! indented_dbg {
+    ($expr:expr) => {{
+        let v = $expr;
+        $crate::util::indented_print::indented_println!(
+            "[{}:{}:{}] {} = {v:#?}",
+            file!(),
+            line!(),
+            column!(),
+            stringify!($expr),
+        );
+        v
+    }};
+}
+
+#[allow(unused)]
+pub(crate) use indented_dbg;

crates/fayalite/src/util/map_trait.rs

@@ -0,0 +1,463 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use std::fmt;
+
+pub enum Entry<'a, M: Map + 'a> {
+    Vacant(M::VacantEntry<'a>),
+    Occupied(M::OccupiedEntry<'a>),
+}
+
+impl<'a, M: Map + 'a> Entry<'a, M> {
+    pub fn and_modify<F: FnOnce(&mut M::Value)>(mut self, f: F) -> Self {
+        if let Self::Occupied(entry) = &mut self {
+            f(entry.get_mut());
+        }
+        self
+    }
+    pub fn insert_entry(self, v: M::Value) -> M::OccupiedEntry<'a> {
+        match self {
+            Self::Vacant(entry) => entry.insert_entry(v),
+            Self::Occupied(mut entry) => {
+                entry.insert(v);
+                entry
+            }
+        }
+    }
+    pub fn key(&self) -> &M::Key {
+        match self {
+            Self::Vacant(entry) => entry.key(),
+            Self::Occupied(entry) => entry.key(),
+        }
+    }
+    pub fn or_default(self) -> &'a mut M::Value
+    where
+        M::Value: Default,
+    {
+        self.or_insert_with(Default::default)
+    }
+    pub fn or_insert(self, v: M::Value) -> &'a mut M::Value {
+        match self {
+            Self::Vacant(entry) => entry.insert(v),
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+    pub fn or_insert_with<F: FnOnce() -> M::Value>(self, f: F) -> &'a mut M::Value {
+        match self {
+            Self::Vacant(entry) => entry.insert(f()),
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+    pub fn or_insert_with_key<F: FnOnce(&M::Key) -> M::Value>(self, f: F) -> &'a mut M::Value {
+        match self {
+            Self::Vacant(entry) => {
+                let v = f(entry.key());
+                entry.insert(v)
+            }
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+}
+
+impl<'a, M: Map<OccupiedEntry<'a>: fmt::Debug, VacantEntry<'a>: fmt::Debug> + 'a> fmt::Debug
+    for Entry<'a, M>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Vacant(v) => f.debug_tuple("Vacant").field(v).finish(),
+            Self::Occupied(v) => f.debug_tuple("Occupied").field(v).finish(),
+        }
+    }
+}
+
+pub trait VacantEntry<'a>: Sized {
+    type Map: Map<VacantEntry<'a> = Self> + 'a;
+    fn insert(self, v: <Self::Map as Map>::Value) -> &'a mut <Self::Map as Map>::Value;
+    fn insert_entry(self, v: <Self::Map as Map>::Value) -> <Self::Map as Map>::OccupiedEntry<'a>;
+    fn into_key(self) -> <Self::Map as Map>::Key;
+    fn key(&self) -> &<Self::Map as Map>::Key;
+}
+
+pub trait OccupiedEntry<'a>: Sized {
+    type Map: Map<OccupiedEntry<'a> = Self> + 'a;
+    fn get(&self) -> &<Self::Map as Map>::Value;
+    fn get_mut(&mut self) -> &mut <Self::Map as Map>::Value;
+    fn insert(&mut self, v: <Self::Map as Map>::Value) -> <Self::Map as Map>::Value;
+    fn into_mut(self) -> &'a mut <Self::Map as Map>::Value;
+    fn key(&self) -> &<Self::Map as Map>::Key;
+    fn remove(self) -> <Self::Map as Map>::Value;
+    fn remove_entry(self) -> (<Self::Map as Map>::Key, <Self::Map as Map>::Value);
+}
+
+pub trait Map:
+    Sized
+    + IntoIterator<Item = (<Self as Map>::Key, <Self as Map>::Value)>
+    + Extend<(<Self as Map>::Key, <Self as Map>::Value)>
+    + FromIterator<(<Self as Map>::Key, <Self as Map>::Value)>
+{
+    type Key;
+    type Value;
+    type IntoKeys: Iterator<Item = Self::Key>;
+    type IntoValues: Iterator<Item = Self::Value>;
+    type Iter<'a>: Iterator<Item = (&'a Self::Key, &'a Self::Value)>
+    where
+        Self: 'a,
+        Self::Key: 'a,
+        Self::Value: 'a;
+    type IterMut<'a>: Iterator<Item = (&'a Self::Key, &'a mut Self::Value)>
+    where
+        Self: 'a,
+        Self::Key: 'a,
+        Self::Value: 'a;
+    type Keys<'a>: Iterator<Item = &'a Self::Key>
+    where
+        Self: 'a,
+        Self::Key: 'a;
+    type Values<'a>: Iterator<Item = &'a Self::Value>
+    where
+        Self: 'a,
+        Self::Value: 'a;
+    type ValuesMut<'a>: Iterator<Item = &'a mut Self::Value>
+    where
+        Self: 'a,
+        Self::Value: 'a;
+    type OccupiedEntry<'a>: OccupiedEntry<'a, Map = Self>
+    where
+        Self: 'a;
+    type VacantEntry<'a>: VacantEntry<'a, Map = Self>
+    where
+        Self: 'a;
+    fn clear(&mut self);
+    fn entry(&mut self, k: Self::Key) -> Entry<'_, Self>;
+    fn insert(&mut self, k: Self::Key, v: Self::Value) -> Option<Self::Value>;
+    fn into_keys(self) -> Self::IntoKeys;
+    fn into_values(self) -> Self::IntoValues;
+    fn is_empty(&self) -> bool;
+    fn iter(&self) -> Self::Iter<'_>;
+    fn iter_mut(&mut self) -> Self::IterMut<'_>;
+    fn keys(&self) -> Self::Keys<'_>;
+    fn len(&self) -> usize;
+    fn retain<F: FnMut(&Self::Key, &mut Self::Value) -> bool>(&mut self, f: F);
+    fn values(&self) -> Self::Values<'_>;
+    fn values_mut(&mut self) -> Self::ValuesMut<'_>;
+}
+
+pub trait MapGet<Q: ?Sized>: Map {
+    fn contains_key(&self, k: &Q) -> bool;
+    fn get(&self, k: &Q) -> Option<&Self::Value>;
+    fn get_mut(&mut self, k: &Q) -> Option<&mut Self::Value>;
+    fn remove(&mut self, k: &Q) -> Option<Self::Value>;
+    fn remove_entry(&mut self, k: &Q) -> Option<(Self::Key, Self::Value)>;
+}
+
+mod hash_map {
+    use super::*;
+    use crate::util::HashMap;
+    use hashbrown::{Equivalent, hash_map};
+    use std::hash::{BuildHasher, Hash};
+
+    impl<K: Eq + Hash, V, H: BuildHasher + Default> Map for HashMap<K, V, H> {
+        type Key = K;
+        type Value = V;
+        type IntoKeys = hash_map::IntoKeys<K, V>;
+        type IntoValues = hash_map::IntoValues<K, V>;
+        type Iter<'a>
+            = hash_map::Iter<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a,
+            Self::Value: 'a;
+        type IterMut<'a>
+            = hash_map::IterMut<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a,
+            Self::Value: 'a;
+        type Keys<'a>
+            = hash_map::Keys<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a;
+        type Values<'a>
+            = hash_map::Values<'a, K, V>
+        where
+            Self: 'a,
+            Self::Value: 'a;
+        type ValuesMut<'a>
+            = hash_map::ValuesMut<'a, K, V>
+        where
+            Self: 'a,
+            Self::Value: 'a;
+        type OccupiedEntry<'a>
+            = hash_map::OccupiedEntry<'a, K, V, H>
+        where
+            Self: 'a;
+        type VacantEntry<'a>
+            = hash_map::VacantEntry<'a, K, V, H>
+        where
+            Self: 'a;
+        fn clear(&mut self) {
+            self.clear();
+        }
+        fn entry(&mut self, k: Self::Key) -> Entry<'_, Self> {
+            use hash_map::Entry::*;
+            match self.entry(k) {
+                Occupied(entry) => Entry::Occupied(entry),
+                Vacant(entry) => Entry::Vacant(entry),
+            }
+        }
+        fn insert(&mut self, k: Self::Key, v: Self::Value) -> Option<Self::Value> {
+            self.insert(k, v)
+        }
+        fn into_keys(self) -> Self::IntoKeys {
+            self.into_keys()
+        }
+        fn into_values(self) -> Self::IntoValues {
+            self.into_values()
+        }
+        fn is_empty(&self) -> bool {
+            self.is_empty()
+        }
+        fn iter(&self) -> Self::Iter<'_> {
+            self.iter()
+        }
+        fn iter_mut(&mut self) -> Self::IterMut<'_> {
+            self.iter_mut()
+        }
+        fn keys(&self) -> Self::Keys<'_> {
+            self.keys()
+        }
+        fn len(&self) -> usize {
+            self.len()
+        }
+        fn retain<F: FnMut(&Self::Key, &mut Self::Value) -> bool>(&mut self, f: F) {
+            self.retain(f);
+        }
+        fn values(&self) -> Self::Values<'_> {
+            self.values()
+        }
+        fn values_mut(&mut self) -> Self::ValuesMut<'_> {
+            self.values_mut()
+        }
+    }
+
+    impl<K: Eq + Hash, V, H: BuildHasher + Default, Q: ?Sized + Hash + Equivalent<K>> MapGet<Q>
+        for HashMap<K, V, H>
+    {
+        fn contains_key(&self, k: &Q) -> bool {
+            self.contains_key(k)
+        }
+        fn get(&self, k: &Q) -> Option<&Self::Value> {
+            self.get(k)
+        }
+        fn get_mut(&mut self, k: &Q) -> Option<&mut Self::Value> {
+            self.get_mut(k)
+        }
+        fn remove(&mut self, k: &Q) -> Option<Self::Value> {
+            self.remove(k)
+        }
+        fn remove_entry(&mut self, k: &Q) -> Option<(Self::Key, Self::Value)> {
+            self.remove_entry(k)
+        }
+    }
+
+    impl<'a, K: Eq + Hash, V, H: BuildHasher + Default> VacantEntry<'a>
+        for hash_map::VacantEntry<'a, K, V, H>
+    {
+        type Map = HashMap<K, V, H>;
+        fn insert(self, v: <Self::Map as Map>::Value) -> &'a mut <Self::Map as Map>::Value {
+            self.insert(v)
+        }
+        fn insert_entry(
+            self,
+            v: <Self::Map as Map>::Value,
+        ) -> <Self::Map as Map>::OccupiedEntry<'a> {
+            self.insert_entry(v)
+        }
+        fn into_key(self) -> <Self::Map as Map>::Key {
+            self.into_key()
+        }
+        fn key(&self) -> &<Self::Map as Map>::Key {
+            self.key()
+        }
+    }
+
+    impl<'a, K: Eq + Hash, V, H: BuildHasher + Default> OccupiedEntry<'a>
+        for hash_map::OccupiedEntry<'a, K, V, H>
+    {
+        type Map = HashMap<K, V, H>;
+        fn get(&self) -> &<Self::Map as Map>::Value {
+            self.get()
+        }
+        fn get_mut(&mut self) -> &mut <Self::Map as Map>::Value {
+            self.get_mut()
+        }
+        fn insert(&mut self, v: <Self::Map as Map>::Value) -> <Self::Map as Map>::Value {
+            self.insert(v)
+        }
+        fn into_mut(self) -> &'a mut <Self::Map as Map>::Value {
+            self.into_mut()
+        }
+        fn key(&self) -> &<Self::Map as Map>::Key {
+            self.key()
+        }
+        fn remove(self) -> <Self::Map as Map>::Value {
+            self.remove()
+        }
+        fn remove_entry(self) -> (<Self::Map as Map>::Key, <Self::Map as Map>::Value) {
+            self.remove_entry()
+        }
+    }
+}
+
+mod btree_map {
+    use super::*;
+    use std::collections::{BTreeMap, btree_map};
+
+    impl<K: Ord, V> Map for BTreeMap<K, V> {
+        type Key = K;
+        type Value = V;
+        type IntoKeys = btree_map::IntoKeys<K, V>;
+        type IntoValues = btree_map::IntoValues<K, V>;
+        type Iter<'a>
+            = btree_map::Iter<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a,
+            Self::Value: 'a;
+        type IterMut<'a>
+            = btree_map::IterMut<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a,
+            Self::Value: 'a;
+        type Keys<'a>
+            = btree_map::Keys<'a, K, V>
+        where
+            Self: 'a,
+            Self::Key: 'a;
+        type Values<'a>
+            = btree_map::Values<'a, K, V>
+        where
+            Self: 'a,
+            Self::Value: 'a;
+        type ValuesMut<'a>
+            = btree_map::ValuesMut<'a, K, V>
+        where
+            Self: 'a,
+            Self::Value: 'a;
+        type OccupiedEntry<'a>
+            = btree_map::OccupiedEntry<'a, K, V>
+        where
+            Self: 'a;
+        type VacantEntry<'a>
+            = btree_map::VacantEntry<'a, K, V>
+        where
+            Self: 'a;
+        fn clear(&mut self) {
+            self.clear();
+        }
+        fn entry(&mut self, k: Self::Key) -> Entry<'_, Self> {
+            use btree_map::Entry::*;
+            match self.entry(k) {
+                Occupied(entry) => Entry::Occupied(entry),
+                Vacant(entry) => Entry::Vacant(entry),
+            }
+        }
+        fn insert(&mut self, k: Self::Key, v: Self::Value) -> Option<Self::Value> {
+            self.insert(k, v)
+        }
+        fn into_keys(self) -> Self::IntoKeys {
+            self.into_keys()
+        }
+        fn into_values(self) -> Self::IntoValues {
+            self.into_values()
+        }
+        fn is_empty(&self) -> bool {
+            self.is_empty()
+        }
+        fn iter(&self) -> Self::Iter<'_> {
+            self.iter()
+        }
+        fn iter_mut(&mut self) -> Self::IterMut<'_> {
+            self.iter_mut()
+        }
+        fn keys(&self) -> Self::Keys<'_> {
+            self.keys()
+        }
+        fn len(&self) -> usize {
+            self.len()
+        }
+        fn retain<F: FnMut(&Self::Key, &mut Self::Value) -> bool>(&mut self, f: F) {
+            self.retain(f);
+        }
+        fn values(&self) -> Self::Values<'_> {
+            self.values()
+        }
+        fn values_mut(&mut self) -> Self::ValuesMut<'_> {
+            self.values_mut()
+        }
+    }
+
+    impl<K: Ord + std::borrow::Borrow<Q>, V, Q: ?Sized + Ord> MapGet<Q> for BTreeMap<K, V> {
+        fn contains_key(&self, k: &Q) -> bool {
+            self.contains_key(k)
+        }
+        fn get(&self, k: &Q) -> Option<&Self::Value> {
+            self.get(k)
+        }
+        fn get_mut(&mut self, k: &Q) -> Option<&mut Self::Value> {
+            self.get_mut(k)
+        }
+        fn remove(&mut self, k: &Q) -> Option<Self::Value> {
+            self.remove(k)
+        }
+        fn remove_entry(&mut self, k: &Q) -> Option<(Self::Key, Self::Value)> {
+            self.remove_entry(k)
+        }
+    }
+
+    impl<'a, K: Ord, V> VacantEntry<'a> for btree_map::VacantEntry<'a, K, V> {
+        type Map = BTreeMap<K, V>;
+        fn insert(self, v: <Self::Map as Map>::Value) -> &'a mut <Self::Map as Map>::Value {
+            self.insert(v)
+        }
+        fn insert_entry(
+            self,
+            v: <Self::Map as Map>::Value,
+        ) -> <Self::Map as Map>::OccupiedEntry<'a> {
+            self.insert_entry(v)
+        }
+        fn into_key(self) -> <Self::Map as Map>::Key {
+            self.into_key()
+        }
+        fn key(&self) -> &<Self::Map as Map>::Key {
+            self.key()
+        }
+    }
+
+    impl<'a, K: Ord, V> OccupiedEntry<'a> for btree_map::OccupiedEntry<'a, K, V> {
+        type Map = BTreeMap<K, V>;
+        fn get(&self) -> &<Self::Map as Map>::Value {
+            self.get()
+        }
+        fn get_mut(&mut self) -> &mut <Self::Map as Map>::Value {
+            self.get_mut()
+        }
+        fn insert(&mut self, v: <Self::Map as Map>::Value) -> <Self::Map as Map>::Value {
+            self.insert(v)
+        }
+        fn into_mut(self) -> &'a mut <Self::Map as Map>::Value {
+            self.into_mut()
+        }
+        fn key(&self) -> &<Self::Map as Map>::Key {
+            self.key()
+        }
+        fn remove(self) -> <Self::Map as Map>::Value {
+            self.remove()
+        }
+        fn remove_entry(self) -> (<Self::Map as Map>::Key, <Self::Map as Map>::Value) {
+            self.remove_entry()
+        }
+    }
+}

crates/fayalite/src/util/ready_valid.rs

@@ -241,15 +241,13 @@ mod tests {
         /// 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,
+                    clk: formal_global_clock(),
                     rst: formal_reset().to_reset(),
                 },
             );
@@ -280,7 +278,7 @@ mod tests {
             #[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()), "");
+            hdl_assume(cd.clk, index_to_check.cmp_lt(capacity.get()), "");
 
             // instantiate and connect the queue
             #[hdl]
@@ -300,13 +298,13 @@ mod tests {
             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()), "");
+                hdl_assert(cd.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()), "");
+                hdl_assert(cd.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), "");
+            hdl_assert(cd.clk, expected_count_reg.cmp_eq(dut.count), "");
 
             // keep an independent write index into the FIFO's circular buffer
             #[hdl]
@@ -374,7 +372,7 @@ mod tests {
                     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), ""),
+                        HdlNone => hdl_assert(cd.clk, HdlOption::is_none(out_firing_data), ""),
                         // If we are indeed receiving some data...
                         HdlSome(data_in) => {
                             #[hdl]
@@ -382,7 +380,9 @@ mod tests {
                                 // ... 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), ""),
+                                HdlSome(data_out) => {
+                                    hdl_assert(cd.clk, data_out.cmp_eq(data_in), "")
+                                }
                                 // If we are receiving, but not transmitting,
                                 // store the received data in the holding
                                 // register.
@@ -397,11 +397,11 @@ mod tests {
                     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), ""),
+                        HdlNone => hdl_assert(cd.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), "");
+                            hdl_assert(cd.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);
@@ -417,17 +417,17 @@ mod tests {
             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), "");
+                hdl_assert(cd.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(cd.clk, inp_index_reg.cmp_eq(dut.dbg.inp_index), "");
-            hdl_assert(clk, out_index_reg.cmp_eq(dut.dbg.out_index), "");
+            hdl_assert(cd.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(cd.clk, inp_index_reg.cmp_lt(capacity.get()), "");
-            hdl_assert(clk, out_index_reg.cmp_lt(capacity.get()), "");
+            hdl_assert(cd.clk, out_index_reg.cmp_lt(capacity.get()), "");
 
             // strongly constrain the state of the holding register
             //
@@ -455,7 +455,7 @@ mod tests {
             connect(expected_stored, pending_reads.cmp_lt(dut.count));
             // sync with the state of the holding register
             hdl_assert(
-                clk,
+                cd.clk,
                 expected_stored.cmp_eq(HdlOption::is_some(stored_reg)),
                 "",
             );

crates/fayalite/src/util/union_find_map.rs

@@ -0,0 +1,352 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::util::{
+    HashMap,
+    map_trait::{self, Map, MapGet, OccupiedEntry as _, VacantEntry as _},
+};
+use petgraph::unionfind::UnionFind;
+use std::{collections::BTreeMap, fmt, marker::PhantomData};
+
+pub struct UnionFindMap<K, V, M = HashMap<K, usize>> {
+    uf: UnionFind<usize>,
+    keys_to_indexes: M,
+    values: Vec<Option<V>>,
+    _phantom: PhantomData<K>,
+}
+
+impl<K: fmt::Debug, V: fmt::Debug, M: Map<Key = K, Value = usize>> fmt::Debug
+    for UnionFindMap<K, V, M>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut indexes_to_keys = vec![None; self.len()];
+        for (k, &index) in self.keys_to_indexes.iter() {
+            indexes_to_keys[index] = Some(k);
+        }
+        let mut debug_map = f.debug_map();
+        for (index, key) in indexes_to_keys.into_iter().enumerate() {
+            if let Some(key) = key {
+                debug_map.key(key);
+            } else {
+                debug_map.key(&fmt::from_fn(|f| {
+                    f.write_str("<<there's a misbehaving key>>")
+                }));
+            }
+            let set_index = self.uf.find(index);
+            debug_map.value(&fmt::from_fn(|f| {
+                write!(f, "@{set_index} ")?;
+                if set_index == index {
+                    let Some(value) = &self.values[index] else {
+                        unreachable!();
+                    };
+                    value.fmt(f)
+                } else {
+                    Ok(())
+                }
+            }));
+        }
+        debug_map.finish()
+    }
+}
+
+impl<K, V, M: Map<Key = K, Value = usize>> UnionFindMap<K, V, M> {
+    /// returns the number of keys, not the number of sets/values
+    pub fn len(&self) -> usize {
+        self.values.len()
+    }
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+    pub fn capacity(&self) -> usize {
+        self.values.capacity()
+    }
+    #[track_caller]
+    pub fn equiv<K1: ?Sized, K2: ?Sized>(&self, k1: &K1, k2: &K2) -> bool
+    where
+        M: MapGet<K1> + MapGet<K2>,
+    {
+        self.try_equiv(k1, k2).expect("key not found")
+    }
+    pub fn try_equiv<K1: ?Sized, K2: ?Sized>(&self, k1: &K1, k2: &K2) -> Option<bool>
+    where
+        M: MapGet<K1> + MapGet<K2>,
+    {
+        let &index1 = self.keys_to_indexes.get(k1)?;
+        let &index2 = self.keys_to_indexes.get(k2)?;
+        Some(self.uf.equiv(index1, index2))
+    }
+    #[track_caller]
+    pub fn find<Q: ?Sized>(&self, k: &Q) -> &V
+    where
+        M: MapGet<Q>,
+    {
+        self.try_find(k).expect("key not found")
+    }
+    pub fn try_find<Q: ?Sized>(&self, k: &Q) -> Option<&V>
+    where
+        M: MapGet<Q>,
+    {
+        let &index = self.keys_to_indexes.get(k)?;
+        self.values[self.uf.find(index)].as_ref()
+    }
+    #[track_caller]
+    pub fn find_mut<Q: ?Sized>(&mut self, k: &Q) -> &mut V
+    where
+        M: MapGet<Q>,
+    {
+        self.try_find_mut(k).expect("key not found")
+    }
+    pub fn try_find_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
+    where
+        M: MapGet<Q>,
+    {
+        let &index = self.keys_to_indexes.get(k)?;
+        self.values[self.uf.find_mut(index)].as_mut()
+    }
+    /// inserts a new key as a new set, otherwise replaces the value for the set containing the passed-in key
+    pub fn insert(&mut self, k: K, v: V) -> Option<V> {
+        match self.entry(k) {
+            Entry::Vacant(entry) => {
+                entry.insert(v);
+                None
+            }
+            Entry::Occupied(mut entry) => Some(entry.insert(v)),
+        }
+    }
+    pub fn entry(&mut self, k: K) -> Entry<'_, K, V, M> {
+        match self.keys_to_indexes.entry(k) {
+            map_trait::Entry::Vacant(keys_to_indexes_entry) => Entry::Vacant(VacantEntry {
+                keys_to_indexes_entry,
+                uf: &mut self.uf,
+                values: &mut self.values,
+            }),
+            map_trait::Entry::Occupied(keys_to_indexes_entry) => {
+                let set_index = self.uf.find_mut(*keys_to_indexes_entry.get());
+                Entry::Occupied(OccupiedEntry {
+                    keys_to_indexes_entry,
+                    set_index,
+                    values: &mut self.values,
+                })
+            }
+        }
+    }
+    /// Unify the two sets containing `k1` and `k2`.
+    /// If the sets were the same, returns `Some((false, value))`,
+    /// otherwise calling `merge` to merge their values and returning `Some((true, value))`.
+    /// Returns `None` if either of the keys weren't found.
+    pub fn try_union<K1: ?Sized, K2: ?Sized, F>(
+        &mut self,
+        k1: &K1,
+        k2: &K2,
+        merge: F,
+    ) -> Option<(bool, &mut V)>
+    where
+        M: MapGet<K1> + MapGet<K2>,
+        F: FnOnce(&K1, V, &K2, V) -> V,
+    {
+        let &index1 = self.keys_to_indexes.get(k1)?;
+        let &index2 = self.keys_to_indexes.get(k2)?;
+        let index1 = self.uf.find_mut(index1);
+        let index2 = self.uf.find_mut(index2);
+        if index1 == index2 {
+            return Some((false, self.values[index1].as_mut()?));
+        }
+        assert!(self.uf.union(index1, index2));
+        let v1 = self.values[index1].take().expect("known to be Some");
+        let v2 = self.values[index2].take().expect("known to be Some");
+        let dest = &mut self.values[self.uf.find_mut(index1)];
+        let dest = dest.insert(merge(k1, v1, k2, v2));
+        Some((true, dest))
+    }
+    /// Unify the two sets containing `k1` and `k2`.
+    /// If the sets were the same, returns `(false, value)`,
+    /// otherwise calling `merge` to merge their values and returning `(true, value)`.
+    /// panics if either of the keys weren't found.
+    #[track_caller]
+    pub fn union<K1: ?Sized, K2: ?Sized, F>(&mut self, k1: &K1, k2: &K2, merge: F) -> (bool, &mut V)
+    where
+        M: MapGet<K1> + MapGet<K2>,
+        F: FnOnce(&K1, V, &K2, V) -> V,
+    {
+        self.try_union(k1, k2, merge).expect("key not found")
+    }
+}
+
+impl<K, V> UnionFindMap<K, V> {
+    pub fn new() -> Self {
+        Self::with_hasher(Default::default())
+    }
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self::with_capacity_and_hasher(capacity, Default::default())
+    }
+}
+
+impl<K, V> UnionFindMap<K, V, BTreeMap<K, usize>> {
+    pub const fn new_btree() -> Self {
+        Self {
+            uf: UnionFind::new_empty(),
+            keys_to_indexes: BTreeMap::new(),
+            values: Vec::new(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<K, V, H> UnionFindMap<K, V, HashMap<K, usize, H>> {
+    pub const fn with_hasher(hash_builder: H) -> Self {
+        Self {
+            uf: UnionFind::new_empty(),
+            keys_to_indexes: HashMap::with_hasher(hash_builder),
+            values: Vec::new(),
+            _phantom: PhantomData,
+        }
+    }
+    pub fn with_capacity_and_hasher(capacity: usize, hash_builder: H) -> Self {
+        Self {
+            uf: UnionFind::with_capacity(capacity),
+            keys_to_indexes: HashMap::with_capacity_and_hasher(capacity, hash_builder),
+            values: Vec::with_capacity(capacity),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<K, V, M: Default> Default for UnionFindMap<K, V, M> {
+    fn default() -> Self {
+        Self {
+            uf: UnionFind::new_empty(),
+            keys_to_indexes: M::default(),
+            values: Vec::new(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+pub struct OccupiedEntry<'a, K, V, M: Map<Key = K, Value = usize> + 'a> {
+    keys_to_indexes_entry: M::OccupiedEntry<'a>,
+    set_index: usize,
+    values: &'a mut [Option<V>],
+}
+
+impl<'a, K, V, M: Map<Key = K, Value = usize> + 'a> OccupiedEntry<'a, K, V, M> {
+    pub fn get(&self) -> &V {
+        let Some(v) = &self.values[self.set_index] else {
+            unreachable!()
+        };
+        v
+    }
+    pub fn get_mut(&mut self) -> &mut V {
+        let Some(v) = &mut self.values[self.set_index] else {
+            unreachable!()
+        };
+        v
+    }
+    /// replaces the value for this set
+    pub fn insert(&mut self, v: V) -> V {
+        std::mem::replace(self.get_mut(), v)
+    }
+    pub fn into_mut(self) -> &'a mut V {
+        let Some(v) = &mut self.values[self.set_index] else {
+            unreachable!()
+        };
+        v
+    }
+    pub fn key(&self) -> &K {
+        self.keys_to_indexes_entry.key()
+    }
+}
+
+pub struct VacantEntry<'a, K, V, M: Map<Key = K, Value = usize> + 'a> {
+    keys_to_indexes_entry: M::VacantEntry<'a>,
+    uf: &'a mut UnionFind<usize>,
+    values: &'a mut Vec<Option<V>>,
+}
+
+impl<'a, K, V, M: Map<Key = K, Value = usize> + 'a> VacantEntry<'a, K, V, M> {
+    /// inserts a new key as a new set
+    pub fn insert(self, v: V) -> &'a mut V {
+        self.insert_entry(v).into_mut()
+    }
+    /// inserts a new key as a new set
+    pub fn insert_entry(self, v: V) -> OccupiedEntry<'a, K, V, M> {
+        let Self {
+            keys_to_indexes_entry,
+            uf,
+            values,
+        } = self;
+        let set_index = uf.new_set();
+        values.push(Some(v));
+        OccupiedEntry {
+            keys_to_indexes_entry: keys_to_indexes_entry.insert_entry(set_index),
+            set_index,
+            values,
+        }
+    }
+    pub fn into_key(self) -> K {
+        self.keys_to_indexes_entry.into_key()
+    }
+    pub fn key(&self) -> &K {
+        self.keys_to_indexes_entry.key()
+    }
+}
+
+pub enum Entry<'a, K, V, M: Map<Key = K, Value = usize> + 'a> {
+    Vacant(VacantEntry<'a, K, V, M>),
+    Occupied(OccupiedEntry<'a, K, V, M>),
+}
+
+impl<'a, K, V, M: Map<Key = K, Value = usize> + 'a> Entry<'a, K, V, M> {
+    pub fn and_modify<F: FnOnce(&mut V)>(mut self, f: F) -> Self {
+        if let Self::Occupied(entry) = &mut self {
+            f(entry.get_mut());
+        }
+        self
+    }
+    /// inserts a new key as a new set, otherwise replaces the value for the set containing the passed-in key
+    pub fn insert_entry(self, v: V) -> OccupiedEntry<'a, K, V, M> {
+        match self {
+            Self::Vacant(entry) => entry.insert_entry(v),
+            Self::Occupied(mut entry) => {
+                entry.insert(v);
+                entry
+            }
+        }
+    }
+    pub fn key(&self) -> &K {
+        match self {
+            Self::Vacant(entry) => entry.key(),
+            Self::Occupied(entry) => entry.key(),
+        }
+    }
+    /// inserts a new key as a new set
+    pub fn or_default(self) -> &'a mut V
+    where
+        V: Default,
+    {
+        self.or_insert_with(V::default)
+    }
+    /// inserts a new key as a new set
+    pub fn or_insert(self, v: V) -> &'a mut V {
+        match self {
+            Self::Vacant(entry) => entry.insert(v),
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+    /// inserts a new key as a new set
+    pub fn or_insert_with<F: FnOnce() -> V>(self, f: F) -> &'a mut V {
+        match self {
+            Self::Vacant(entry) => entry.insert(f()),
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+    /// inserts a new key as a new set
+    pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, f: F) -> &'a mut V {
+        match self {
+            Self::Vacant(entry) => {
+                let v = f(entry.key());
+                entry.insert(v)
+            }
+            Self::Occupied(entry) => entry.into_mut(),
+        }
+    }
+}

crates/fayalite/src/vendor/xilinx/yosys_nextpnr_prjxray.rs

@@ -595,6 +595,9 @@ impl<W: fmt::Write> Visitor for XdcFileWriter<W> {
                         v,
                         instance.source_location(),
                     )? {},
+                    TargetBase::FormalInput(_) | TargetBase::SimIoForGlobal(_) => {
+                        unreachable!("base.is_valid_annotation_target() is known to be false")
+                    }
                 }
             }
         }

crates/fayalite/src/wire.rs

@@ -58,11 +58,13 @@ impl<T: Type> Wire<T> {
             ty: T::from_canonical(ty),
         }
     }
+    #[track_caller]
     pub fn new_unchecked(
         scoped_name: ScopedNameId,
         source_location: SourceLocation,
         ty: T,
     ) -> Self {
+        scoped_name.0.assert_is_name_id();
         Self {
             name: scoped_name,
             source_location,
@@ -76,7 +78,7 @@ impl<T: Type> Wire<T> {
         self.containing_module_name_id().0
     }
     pub fn containing_module_name_id(&self) -> NameId {
-        self.name.0
+        self.name.0.unwrap_name_id()
     }
     pub fn name(&self) -> Interned<str> {
         self.name_id().0

crates/fayalite/tests/expected/my_test.md

@@ -0,0 +1,6 @@
+<!--
+SPDX-License-Identifier: LGPL-3.0-or-later
+See Notices.txt for copyright information
+-->
+
+`my_test.vcd` is used in the doctest of `fayalite::testing::checked_vcd_output`

crates/fayalite/tests/expected/my_test.vcd

@@ -0,0 +1,13 @@
+$timescale 1 ps $end
+$scope module my_module $end
+$var wire 8 gAF7X a $end
+$var wire 8 QS=a/ b $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b0 gAF7X
+b0 QS=a/
+$end
+#1000000
+b1100100 gAF7X
+b101010 QS=a/

crates/fayalite/tests/module.rs

@@ -709,44 +709,35 @@ circuit check_enum_cmp_eq:
         input lhs: Ty0 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty0 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire _cast_enum_to_bits_expr: UInt<10>
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        match lhs:
-        match lhs: @[module-XXXXXXXXXX.rs 5:1]
             A:
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<10>(0)
-                    A:
+            B(_cast_enum_to_bits_expr_B):
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, pad(cat(_cast_enum_to_bits_expr_B, UInt<2>(1)), 10)
-                    B(_match_arm_value):
+            C(_cast_enum_to_bits_expr_C):
-                        skip
+                wire _cast_array_to_bits_expr: UInt<1>[3]
-                    C(_match_arm_value_1):
+                connect _cast_array_to_bits_expr[0], _cast_enum_to_bits_expr_C[0]
-                        skip
+                connect _cast_array_to_bits_expr[1], _cast_enum_to_bits_expr_C[1]
-            B(_match_arm_value_2):
+                connect _cast_array_to_bits_expr[2], _cast_enum_to_bits_expr_C[2]
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_to_bits_expr: UInt<3>
-                    A:
+                connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
-                        skip
+                connect _cast_enum_to_bits_expr, pad(cat(_cast_to_bits_expr, UInt<2>(2)), 10)
-                    B(_match_arm_value_3):
+        wire _cast_enum_to_bits_expr_1: UInt<10>
-                        connect TestEnum_cmp_eq, eq(_match_arm_value_2, _match_arm_value_3) @[module-XXXXXXXXXX.rs 5:1]
+        match rhs:
-                    C(_match_arm_value_4):
+            A:
-                        skip
+                connect _cast_enum_to_bits_expr_1, UInt<10>(0)
-            C(_match_arm_value_5):
+            B(_cast_enum_to_bits_expr_B_1):
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr_1, pad(cat(_cast_enum_to_bits_expr_B_1, UInt<2>(1)), 10)
-                    A:
+            C(_cast_enum_to_bits_expr_C_1):
-                        skip
+                wire _cast_array_to_bits_expr_1: UInt<1>[3]
-                    B(_match_arm_value_6):
+                connect _cast_array_to_bits_expr_1[0], _cast_enum_to_bits_expr_C_1[0]
-                        skip
+                connect _cast_array_to_bits_expr_1[1], _cast_enum_to_bits_expr_C_1[1]
-                    C(_match_arm_value_7):
+                connect _cast_array_to_bits_expr_1[2], _cast_enum_to_bits_expr_C_1[2]
-                        wire _array_literal_expr: UInt<1>[3]
+                wire _cast_to_bits_expr_1: UInt<3>
-                        connect _array_literal_expr[0], eq(_match_arm_value_5[0], _match_arm_value_7[0])
+                connect _cast_to_bits_expr_1, cat(_cast_array_to_bits_expr_1[2], cat(_cast_array_to_bits_expr_1[1], _cast_array_to_bits_expr_1[0]))
-                        connect _array_literal_expr[1], eq(_match_arm_value_5[1], _match_arm_value_7[1])
+                connect _cast_enum_to_bits_expr_1, pad(cat(_cast_to_bits_expr_1, UInt<2>(2)), 10)
-                        connect _array_literal_expr[2], eq(_match_arm_value_5[2], _match_arm_value_7[2])
+        connect eq, eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 5:1]
-                        wire _cast_array_to_bits_expr: UInt<1>[3]
-                        connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
-                        connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
-                        connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
-                        wire _cast_to_bits_expr: UInt<3>
-                        connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
-                        connect TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -764,92 +755,53 @@ circuit check_enum_cmp_eq:
         input lhs: Ty1 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty1 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        match lhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr: UInt<2>
+        match lhs.tag:
             A:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(0)
-                    A:
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-                    B:
-                        skip
-                    C:
-                        skip
             B:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(1)
-                    A:
-                        skip
-                    B:
-                        connect TestEnum_cmp_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
-                    C:
-                        skip
             C:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_enum_to_bits_expr, UInt<2>(2)
-                    A:
+        wire _cast_enum_to_bits_expr_1: UInt<2>
-                        skip
+        match rhs.tag:
-                    B:
+            A:
-                        skip
+                connect _cast_enum_to_bits_expr_1, UInt<2>(0)
-                    C:
+            B:
-                        wire _array_literal_expr: UInt<1>[3]
+                connect _cast_enum_to_bits_expr_1, UInt<2>(1)
-                        wire _cast_bits_to_array_expr: UInt<1>[3]
+            C:
-                        wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_enum_to_bits_expr_1, UInt<2>(2)
-                        connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+        when eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1): @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+            match lhs.tag: @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                A:
-                        connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                    connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                B:
-                        connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                    connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-                        wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                C:
-                        wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                    wire _cast_bits_to_array_expr: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
+                    wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                    connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
+                    connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-                        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
+                    connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
+                    connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-                        connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
+                    connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-                        connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
+                    connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-                        wire _cast_bits_to_array_expr_2: UInt<1>[3]
+                    wire _cast_bits_to_array_expr_1: UInt<1>[3]
-                        wire _cast_bits_to_array_expr_flattened_2: UInt<1>[3]
+                    wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened_2[0], bits(bits(lhs.body, 2, 0), 0, 0)
+                    connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr_2[0], _cast_bits_to_array_expr_flattened_2[0]
+                    connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-                        connect _cast_bits_to_array_expr_flattened_2[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                    connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_flattened_2[1]
+                    connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-                        connect _cast_bits_to_array_expr_flattened_2[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                    connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-                        connect _cast_bits_to_array_expr_2[2], _cast_bits_to_array_expr_flattened_2[2]
+                    connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-                        wire _cast_bits_to_array_expr_3: UInt<1>[3]
+                    wire _array_structural_eq: UInt<1>
-                        wire _cast_bits_to_array_expr_flattened_3: UInt<1>[3]
+                    connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
-                        connect _cast_bits_to_array_expr_flattened_3[0], bits(bits(rhs.body, 2, 0), 0, 0)
+                    wire _array_structural_eq_1: UInt<1>
-                        connect _cast_bits_to_array_expr_3[0], _cast_bits_to_array_expr_flattened_3[0]
+                    connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
-                        connect _cast_bits_to_array_expr_flattened_3[1], bits(bits(rhs.body, 2, 0), 1, 1)
+                    connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
-                        connect _cast_bits_to_array_expr_3[1], _cast_bits_to_array_expr_flattened_3[1]
-                        connect _cast_bits_to_array_expr_flattened_3[2], bits(bits(rhs.body, 2, 0), 2, 2)
-                        connect _cast_bits_to_array_expr_3[2], _cast_bits_to_array_expr_flattened_3[2]
-                        connect _array_literal_expr[1], eq(_cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_3[1])
-                        wire _cast_bits_to_array_expr_4: UInt<1>[3]
-                        wire _cast_bits_to_array_expr_flattened_4: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened_4[0], bits(bits(lhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr_4[0], _cast_bits_to_array_expr_flattened_4[0]
-                        connect _cast_bits_to_array_expr_flattened_4[1], bits(bits(lhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr_4[1], _cast_bits_to_array_expr_flattened_4[1]
-                        connect _cast_bits_to_array_expr_flattened_4[2], bits(bits(lhs.body, 2, 0), 2, 2)
-                        connect _cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_flattened_4[2]
-                        wire _cast_bits_to_array_expr_5: UInt<1>[3]
-                        wire _cast_bits_to_array_expr_flattened_5: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened_5[0], bits(bits(rhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr_5[0], _cast_bits_to_array_expr_flattened_5[0]
-                        connect _cast_bits_to_array_expr_flattened_5[1], bits(bits(rhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr_5[1], _cast_bits_to_array_expr_flattened_5[1]
-                        connect _cast_bits_to_array_expr_flattened_5[2], bits(bits(rhs.body, 2, 0), 2, 2)
-                        connect _cast_bits_to_array_expr_5[2], _cast_bits_to_array_expr_flattened_5[2]
-                        connect _array_literal_expr[2], eq(_cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_5[2])
-                        wire _cast_array_to_bits_expr: UInt<1>[3]
-                        connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
-                        connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
-                        connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
-                        wire _cast_to_bits_expr: UInt<3>
-                        connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
-                        connect TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -866,83 +818,36 @@ circuit check_enum_cmp_eq:
         input lhs: Ty0 @[module-XXXXXXXXXX.rs 2:1]
         input rhs: Ty0 @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        when eq(lhs.tag, rhs.tag): @[module-XXXXXXXXXX.rs 1:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+            when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                skip
+            else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
-        else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+            else:
-                skip
+                wire _cast_bits_to_array_expr: UInt<1>[3]
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                connect TestEnum_cmp_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-        else when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            skip
+                connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-        else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-            skip
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-        else:
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _array_literal_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _array_structural_eq: UInt<1>
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
-            wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                wire _array_structural_eq_1: UInt<1>
-            connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(rhs.body, 2, 0), 0, 0)
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
-            connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
-            connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
-            wire _cast_bits_to_array_expr_2: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_2: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_2[0], bits(bits(lhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_2[0], _cast_bits_to_array_expr_flattened_2[0]
-            connect _cast_bits_to_array_expr_flattened_2[1], bits(bits(lhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_flattened_2[1]
-            connect _cast_bits_to_array_expr_flattened_2[2], bits(bits(lhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_2[2], _cast_bits_to_array_expr_flattened_2[2]
-            wire _cast_bits_to_array_expr_3: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_3: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_3[0], bits(bits(rhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_3[0], _cast_bits_to_array_expr_flattened_3[0]
-            connect _cast_bits_to_array_expr_flattened_3[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_3[1], _cast_bits_to_array_expr_flattened_3[1]
-            connect _cast_bits_to_array_expr_flattened_3[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_3[2], _cast_bits_to_array_expr_flattened_3[2]
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_3[1])
-            wire _cast_bits_to_array_expr_4: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_4: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_4[0], bits(bits(lhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_4[0], _cast_bits_to_array_expr_flattened_4[0]
-            connect _cast_bits_to_array_expr_flattened_4[1], bits(bits(lhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_4[1], _cast_bits_to_array_expr_flattened_4[1]
-            connect _cast_bits_to_array_expr_flattened_4[2], bits(bits(lhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_flattened_4[2]
-            wire _cast_bits_to_array_expr_5: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_5: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_5[0], bits(bits(rhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_5[0], _cast_bits_to_array_expr_flattened_5[0]
-            connect _cast_bits_to_array_expr_flattened_5[1], bits(bits(rhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_5[1], _cast_bits_to_array_expr_flattened_5[1]
-            connect _cast_bits_to_array_expr_flattened_5[2], bits(bits(rhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_5[2], _cast_bits_to_array_expr_flattened_5[2]
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_5[2])
-            wire _cast_array_to_bits_expr: UInt<1>[3]
-            connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
-            connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
-            connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
-            wire _cast_to_bits_expr: UInt<3>
-            connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
-            connect TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -958,83 +863,36 @@ circuit check_enum_cmp_eq:
         input lhs: UInt<10> @[module-XXXXXXXXXX.rs 2:1]
         input rhs: UInt<10> @[module-XXXXXXXXXX.rs 3:1]
         output eq: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
-        wire TestEnum_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
-        when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+        when eq(bits(lhs, 1, 0), bits(rhs, 1, 0)): @[module-XXXXXXXXXX.rs 1:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
+            when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
-                skip
+            else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
-        else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect __enum_structural_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+            else:
-                skip
+                wire _cast_bits_to_array_expr: UInt<1>[3]
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                connect TestEnum_cmp_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            skip
+                connect _cast_bits_to_array_expr_flattened[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
+                connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-            skip
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
-        else:
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _array_literal_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_flattened[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
+                connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _array_structural_eq: UInt<1>
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                connect _array_structural_eq, and(eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0]), eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1]))
-            wire _cast_bits_to_array_expr_flattened_1: UInt<1>[3]
+                wire _array_structural_eq_1: UInt<1>
-            connect _cast_bits_to_array_expr_flattened_1[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
-            connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
-            connect _cast_bits_to_array_expr_flattened_1[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
-            connect _cast_bits_to_array_expr_flattened_1[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_1[2], _cast_bits_to_array_expr_flattened_1[2]
-            connect _array_literal_expr[0], eq(_cast_bits_to_array_expr[0], _cast_bits_to_array_expr_1[0])
-            wire _cast_bits_to_array_expr_2: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_2: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_2[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_2[0], _cast_bits_to_array_expr_flattened_2[0]
-            connect _cast_bits_to_array_expr_flattened_2[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_flattened_2[1]
-            connect _cast_bits_to_array_expr_flattened_2[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_2[2], _cast_bits_to_array_expr_flattened_2[2]
-            wire _cast_bits_to_array_expr_3: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_3: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_3[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_3[0], _cast_bits_to_array_expr_flattened_3[0]
-            connect _cast_bits_to_array_expr_flattened_3[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_3[1], _cast_bits_to_array_expr_flattened_3[1]
-            connect _cast_bits_to_array_expr_flattened_3[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_3[2], _cast_bits_to_array_expr_flattened_3[2]
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr_2[1], _cast_bits_to_array_expr_3[1])
-            wire _cast_bits_to_array_expr_4: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_4: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_4[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_4[0], _cast_bits_to_array_expr_flattened_4[0]
-            connect _cast_bits_to_array_expr_flattened_4[1], bits(bits(bits(lhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_4[1], _cast_bits_to_array_expr_flattened_4[1]
-            connect _cast_bits_to_array_expr_flattened_4[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_flattened_4[2]
-            wire _cast_bits_to_array_expr_5: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_5: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened_5[0], bits(bits(bits(rhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr_5[0], _cast_bits_to_array_expr_flattened_5[0]
-            connect _cast_bits_to_array_expr_flattened_5[1], bits(bits(bits(rhs, 9, 2), 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr_5[1], _cast_bits_to_array_expr_flattened_5[1]
-            connect _cast_bits_to_array_expr_flattened_5[2], bits(bits(bits(rhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr_5[2], _cast_bits_to_array_expr_flattened_5[2]
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr_4[2], _cast_bits_to_array_expr_5[2])
-            wire _cast_array_to_bits_expr: UInt<1>[3]
-            connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
-            connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
-            connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
-            wire _cast_to_bits_expr: UInt<3>
-            connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
-            connect TestEnum_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        connect eq, TestEnum_cmp_eq @[module-XXXXXXXXXX.rs 6:1]
 ",
     };
 }
@@ -3779,20 +3637,176 @@ circuit check_formal: %[[
         input pred1: UInt<1> @[module-XXXXXXXXXX.rs 6:1]
         input pred2: UInt<1> @[module-XXXXXXXXXX.rs 7:1]
         input pred3: UInt<1> @[module-XXXXXXXXXX.rs 8:1]
-        inst formal_reset of formal_reset @[formal.rs 185:24]
+        inst formal_reset of formal_reset @[builtin 1:1]
         assert(clk, pred1, and(en1, not(formal_reset.rst)), "en check 1") @[module-XXXXXXXXXX.rs 9:1]
-        inst formal_reset_1 of formal_reset @[formal.rs 185:24]
+        assume(clk, pred2, and(en2, not(formal_reset.rst)), "en check 2") @[module-XXXXXXXXXX.rs 10:1]
-        assume(clk, pred2, and(en2, not(formal_reset_1.rst)), "en check 2") @[module-XXXXXXXXXX.rs 10:1]
+        cover(clk, pred3, and(en3, not(formal_reset.rst)), "en check 3") @[module-XXXXXXXXXX.rs 11:1]
-        inst formal_reset_2 of formal_reset @[formal.rs 185:24]
+        assert(clk, pred1, and(UInt<1>(0h1), not(formal_reset.rst)), "check 1") @[module-XXXXXXXXXX.rs 12:1]
-        cover(clk, pred3, and(en3, not(formal_reset_2.rst)), "en check 3") @[module-XXXXXXXXXX.rs 11:1]
+        assume(clk, pred2, and(UInt<1>(0h1), not(formal_reset.rst)), "check 2") @[module-XXXXXXXXXX.rs 13:1]
-        inst formal_reset_3 of formal_reset @[formal.rs 185:24]
+        cover(clk, pred3, and(UInt<1>(0h1), not(formal_reset.rst)), "check 3") @[module-XXXXXXXXXX.rs 14:1]
-        assert(clk, pred1, and(UInt<1>(0h1), not(formal_reset_3.rst)), "check 1") @[module-XXXXXXXXXX.rs 12:1]
+    extmodule formal_reset: @[builtin 1:1]
-        inst formal_reset_4 of formal_reset @[formal.rs 185:24]
+        output rst: UInt<1> @[builtin 1:1]
-        assume(clk, pred2, and(UInt<1>(0h1), not(formal_reset_4.rst)), "check 2") @[module-XXXXXXXXXX.rs 13:1]
+        defname = __fayalite_formal_reset
-        inst formal_reset_5 of formal_reset @[formal.rs 185:24]
+"#,
-        cover(clk, pred3, and(UInt<1>(0h1), not(formal_reset_5.rst)), "check 3") @[module-XXXXXXXXXX.rs 14:1]
+    };
-    extmodule formal_reset: @[formal.rs 169:5]
+}
-        output rst: UInt<1> @[formal.rs 172:32]
+
+#[hdl_module(outline_generated)]
+pub fn check_formal_input() {
+    #[hdl]
+    let bool_in: Bool = m.input();
+    #[hdl]
+    let bool_out: Bool = m.output();
+    #[hdl]
+    let any_const_out1: Bool = m.output();
+    #[hdl]
+    let any_const_out2: UInt<16> = m.output();
+    #[hdl]
+    let any_const_out3: SInt<12> = m.output();
+    #[hdl]
+    let any_seq_out: UInt<10> = m.output();
+    #[hdl]
+    let all_const_out: UInt<10> = m.output();
+    #[hdl]
+    let all_seq_out: UInt<10> = m.output();
+
+    #[hdl]
+    let bool_reg = reg_builder()
+        .clock_domain(
+            #[hdl]
+            ClockDomain {
+                clk: formal_global_clock(),
+                rst: formal_reset(),
+            },
+        )
+        .reset(false);
+
+    connect(bool_reg, bool_in);
+    connect(bool_out, bool_reg);
+    connect(any_const_out1, any_const(StaticType::TYPE));
+    connect(any_const_out2, any_const(StaticType::TYPE));
+    connect(any_const_out3, any_const(StaticType::TYPE));
+    connect(any_seq_out, any_seq(StaticType::TYPE));
+    connect(all_const_out, all_const(StaticType::TYPE));
+    connect(all_seq_out, all_seq(StaticType::TYPE));
+}
+
+#[test]
+fn test_formal_input() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_formal_input();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        "/test/check_formal_input.fir": r#"FIRRTL version 3.2.0
+circuit check_formal_input: %[[
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "gclk",
+    "target": "~check_formal_input|check_formal_input>formal_global_clock"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>formal_global_clock"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "anyconst",
+    "target": "~check_formal_input|check_formal_input>any_const"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>any_const"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "anyconst",
+    "target": "~check_formal_input|check_formal_input>any_const_1"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>any_const_1"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "anyconst",
+    "target": "~check_formal_input|check_formal_input>any_const_2"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>any_const_2"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "anyseq",
+    "target": "~check_formal_input|check_formal_input>any_seq"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>any_seq"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "allconst",
+    "target": "~check_formal_input|check_formal_input>all_const"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>all_const"
+  },
+  {
+    "class": "firrtl.AttributeAnnotation",
+    "description": "allseq",
+    "target": "~check_formal_input|check_formal_input>all_seq"
+  },
+  {
+    "class": "firrtl.transforms.DontTouchAnnotation",
+    "target": "~check_formal_input|check_formal_input>all_seq"
+  },
+  {
+    "class": "firrtl.transforms.BlackBoxInlineAnno",
+    "name": "fayalite_formal_reset.v",
+    "text": "module __fayalite_formal_reset(output rst);\n    assign rst = $initstate;\nendmodule\n",
+    "target": "~check_formal_input|formal_reset"
+  }
+]]
+    type Ty0 = {clk: Clock, rst: UInt<1>}
+    type Ty1 = {rst: UInt<1>}
+    module check_formal_input: @[module-XXXXXXXXXX.rs 1:1]
+        input bool_in: UInt<1> @[module-XXXXXXXXXX.rs 2:1]
+        output bool_out: UInt<1> @[module-XXXXXXXXXX.rs 3:1]
+        output any_const_out1: UInt<1> @[module-XXXXXXXXXX.rs 4:1]
+        output any_const_out2: UInt<16> @[module-XXXXXXXXXX.rs 5:1]
+        output any_const_out3: SInt<12> @[module-XXXXXXXXXX.rs 6:1]
+        output any_seq_out: UInt<10> @[module-XXXXXXXXXX.rs 7:1]
+        output all_const_out: UInt<10> @[module-XXXXXXXXXX.rs 8:1]
+        output all_seq_out: UInt<10> @[module-XXXXXXXXXX.rs 9:1]
+        wire _bundle_literal_expr_1: Ty0
+        connect _bundle_literal_expr_1.clk, asClock(UInt<1>(0h0))
+        connect _bundle_literal_expr_1.rst, UInt<1>(0h0)
+        reg formal_global_clock: UInt<1>, _bundle_literal_expr_1.clk @[builtin 1:1]
+        inst formal_reset of formal_reset @[builtin 1:1]
+        reg any_const: UInt<1>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 13:1]
+        reg any_const_1: UInt<16>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 15:1]
+        reg any_const_2: SInt<12>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 17:1]
+        reg any_seq: UInt<10>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 19:1]
+        reg all_const: UInt<10>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 21:1]
+        reg all_seq: UInt<10>, _bundle_literal_expr_1.clk @[module-XXXXXXXXXX.rs 23:1]
+        wire _bundle_literal_expr: Ty0
+        connect _bundle_literal_expr.clk, asClock(formal_global_clock)
+        connect _bundle_literal_expr.rst, formal_reset.rst
+        regreset bool_reg: UInt<1>, _bundle_literal_expr.clk, _bundle_literal_expr.rst, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 10:1]
+        connect bool_reg, bool_in @[module-XXXXXXXXXX.rs 11:1]
+        connect bool_out, bool_reg @[module-XXXXXXXXXX.rs 12:1]
+        connect any_const_out1, any_const @[module-XXXXXXXXXX.rs 14:1]
+        connect any_const_out2, any_const_1 @[module-XXXXXXXXXX.rs 16:1]
+        connect any_const_out3, any_const_2 @[module-XXXXXXXXXX.rs 18:1]
+        connect any_seq_out, any_seq @[module-XXXXXXXXXX.rs 20:1]
+        connect all_const_out, all_const @[module-XXXXXXXXXX.rs 22:1]
+        connect all_seq_out, all_seq @[module-XXXXXXXXXX.rs 24:1]
+    extmodule formal_reset: @[builtin 1:1]
+        output rst: UInt<1> @[builtin 1:1]
         defname = __fayalite_formal_reset
 "#,
     };
@@ -3925,21 +3939,10 @@ circuit check_enum_connect_any:
                             connect __connect_variant_body_1, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 8:1]
                         HdlSome:
                             wire __connect_variant_body_2: SInt<1> @[module-XXXXXXXXXX.rs 8:1]
-                            wire _cast_bits_to_bundle_expr_1: Ty5
-                            wire _cast_bits_to_bundle_expr_flattened_1: Ty6
-                            connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(bits(i2.body, 2, 0), 0, 0)
-                            wire _cast_bits_to_enum_expr_1: Ty3
-                            when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_1.tag, 0)):
-                                connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome|}(HdlNone)
-                            else:
-                                connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome|}(HdlSome)
-                            connect _cast_bits_to_bundle_expr_1.tag, _cast_bits_to_enum_expr_1
-                            connect _cast_bits_to_bundle_expr_flattened_1.body, bits(bits(i2.body, 2, 0), 2, 1)
-                            connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
                             ; connect different types:
                             ; lhs: SInt<1>
                             ; rhs: SInt<2>
-                            connect __connect_variant_body_2, asSInt(bits(_cast_bits_to_bundle_expr_1.body, 1, 0)) @[module-XXXXXXXXXX.rs 8:1]
+                            connect __connect_variant_body_2, asSInt(bits(_cast_bits_to_bundle_expr.body, 1, 0)) @[module-XXXXXXXXXX.rs 8:1]
                             wire _bundle_literal_expr_2: Ty4
                             connect _bundle_literal_expr_2.tag, {|HdlNone, HdlSome|}(HdlSome)
                             connect _bundle_literal_expr_2.body, asUInt(__connect_variant_body_2)
@@ -3961,18 +3964,18 @@ circuit check_enum_connect_any:
                     connect o1, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 8:1]
                 C:
                     wire __connect_variant_body_3: Ty8 @[module-XXXXXXXXXX.rs 8:1]
-                    wire _cast_bits_to_bundle_expr_2: Ty8
+                    wire _cast_bits_to_bundle_expr_1: Ty8
-                    wire _cast_bits_to_bundle_expr_flattened_2: Ty9
+                    wire _cast_bits_to_bundle_expr_flattened_1: Ty9
-                    connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(bits(i2.body, 0, 0), 0, 0)
+                    connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(bits(i2.body, 0, 0), 0, 0)
-                    wire _cast_bits_to_enum_expr_2: Ty3
+                    wire _cast_bits_to_enum_expr_1: Ty3
-                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_2.tag, 0)):
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_1.tag, 0)):
-                        connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlNone)
+                        connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome|}(HdlNone)
                     else:
-                        connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlSome)
+                        connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome|}(HdlSome)
-                    connect _cast_bits_to_bundle_expr_2.tag, _cast_bits_to_enum_expr_2
+                    connect _cast_bits_to_bundle_expr_1.tag, _cast_bits_to_enum_expr_1
-                    connect _cast_bits_to_bundle_expr_flattened_2.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_flattened_1.body, UInt<0>(0)
-                    connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
+                    connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
-                    connect __connect_variant_body_3, _cast_bits_to_bundle_expr_2 @[module-XXXXXXXXXX.rs 8:1]
+                    connect __connect_variant_body_3, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 8:1]
                     wire _bundle_literal_expr_4: Ty1
                     connect _bundle_literal_expr_4.tag, {|A, B, C|}(C)
                     wire _cast_bundle_to_bits_expr_1: Ty9
@@ -4001,18 +4004,18 @@ circuit check_enum_connect_any:
                     connect o2, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 9:1]
                 B:
                     wire __connect_variant_body_5: Ty5 @[module-XXXXXXXXXX.rs 9:1]
-                    wire _cast_bits_to_bundle_expr_3: Ty4
+                    wire _cast_bits_to_bundle_expr_2: Ty4
-                    wire _cast_bits_to_bundle_expr_flattened_3: Ty7
+                    wire _cast_bits_to_bundle_expr_flattened_2: Ty7
-                    connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(bits(i1.body, 1, 0), 0, 0)
+                    connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(bits(i1.body, 1, 0), 0, 0)
-                    wire _cast_bits_to_enum_expr_3: Ty3
+                    wire _cast_bits_to_enum_expr_2: Ty3
-                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_3.tag, 0)):
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_2.tag, 0)):
-                        connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlNone)
+                        connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlNone)
                     else:
-                        connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlSome)
+                        connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlSome)
-                    connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_enum_expr_3
+                    connect _cast_bits_to_bundle_expr_2.tag, _cast_bits_to_enum_expr_2
-                    connect _cast_bits_to_bundle_expr_flattened_3.body, bits(bits(i1.body, 1, 0), 1, 1)
+                    connect _cast_bits_to_bundle_expr_flattened_2.body, bits(bits(i1.body, 1, 0), 1, 1)
-                    connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
+                    connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
-                    match _cast_bits_to_bundle_expr_3.tag: @[module-XXXXXXXXXX.rs 9:1]
+                    match _cast_bits_to_bundle_expr_2.tag: @[module-XXXXXXXXXX.rs 9:1]
                         HdlNone:
                             wire _bundle_literal_expr_6: Ty5
                             connect _bundle_literal_expr_6.tag, {|HdlNone, HdlSome|}(HdlNone)
@@ -4020,21 +4023,10 @@ circuit check_enum_connect_any:
                             connect __connect_variant_body_5, _bundle_literal_expr_6 @[module-XXXXXXXXXX.rs 9:1]
                         HdlSome:
                             wire __connect_variant_body_6: SInt<2> @[module-XXXXXXXXXX.rs 9:1]
-                            wire _cast_bits_to_bundle_expr_4: Ty4
-                            wire _cast_bits_to_bundle_expr_flattened_4: Ty7
-                            connect _cast_bits_to_bundle_expr_flattened_4.tag, bits(bits(i1.body, 1, 0), 0, 0)
-                            wire _cast_bits_to_enum_expr_4: Ty3
-                            when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_4.tag, 0)):
-                                connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome|}(HdlNone)
-                            else:
-                                connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome|}(HdlSome)
-                            connect _cast_bits_to_bundle_expr_4.tag, _cast_bits_to_enum_expr_4
-                            connect _cast_bits_to_bundle_expr_flattened_4.body, bits(bits(i1.body, 1, 0), 1, 1)
-                            connect _cast_bits_to_bundle_expr_4.body, _cast_bits_to_bundle_expr_flattened_4.body
                             ; connect different types:
                             ; lhs: SInt<2>
                             ; rhs: SInt<1>
-                            connect __connect_variant_body_6, asSInt(bits(_cast_bits_to_bundle_expr_4.body, 0, 0)) @[module-XXXXXXXXXX.rs 9:1]
+                            connect __connect_variant_body_6, asSInt(bits(_cast_bits_to_bundle_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 9:1]
                             wire _bundle_literal_expr_7: Ty5
                             connect _bundle_literal_expr_7.tag, {|HdlNone, HdlSome|}(HdlSome)
                             connect _bundle_literal_expr_7.body, asUInt(__connect_variant_body_6)
@@ -4056,18 +4048,18 @@ circuit check_enum_connect_any:
                     connect o2, _bundle_literal_expr_8 @[module-XXXXXXXXXX.rs 9:1]
                 C:
                     wire __connect_variant_body_7: Ty8 @[module-XXXXXXXXXX.rs 9:1]
-                    wire _cast_bits_to_bundle_expr_5: Ty8
+                    wire _cast_bits_to_bundle_expr_3: Ty8
-                    wire _cast_bits_to_bundle_expr_flattened_5: Ty9
+                    wire _cast_bits_to_bundle_expr_flattened_3: Ty9
-                    connect _cast_bits_to_bundle_expr_flattened_5.tag, bits(bits(i1.body, 0, 0), 0, 0)
+                    connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(bits(i1.body, 0, 0), 0, 0)
-                    wire _cast_bits_to_enum_expr_5: Ty3
+                    wire _cast_bits_to_enum_expr_3: Ty3
-                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_5.tag, 0)):
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_3.tag, 0)):
-                        connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome|}(HdlNone)
+                        connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlNone)
                     else:
-                        connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome|}(HdlSome)
+                        connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlSome)
-                    connect _cast_bits_to_bundle_expr_5.tag, _cast_bits_to_enum_expr_5
+                    connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_enum_expr_3
-                    connect _cast_bits_to_bundle_expr_flattened_5.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_flattened_3.body, UInt<0>(0)
-                    connect _cast_bits_to_bundle_expr_5.body, _cast_bits_to_bundle_expr_flattened_5.body
+                    connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
-                    connect __connect_variant_body_7, _cast_bits_to_bundle_expr_5 @[module-XXXXXXXXXX.rs 9:1]
+                    connect __connect_variant_body_7, _cast_bits_to_bundle_expr_3 @[module-XXXXXXXXXX.rs 9:1]
                     wire _bundle_literal_expr_9: Ty2
                     connect _bundle_literal_expr_9.tag, {|A, B, C|}(C)
                     wire _cast_bundle_to_bits_expr_3: Ty9
@@ -4134,16 +4126,10 @@ circuit check_enum_connect_any:
                     connect __connect_variant_body_1, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 8:1]
                 else:
                     wire __connect_variant_body_2: SInt<1> @[module-XXXXXXXXXX.rs 8:1]
-                    wire _cast_bits_to_bundle_expr_1: Ty3
-                    wire _cast_bits_to_bundle_expr_flattened_1: Ty3
-                    connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(bits(i2.body, 2, 0), 0, 0)
-                    connect _cast_bits_to_bundle_expr_1.tag, _cast_bits_to_bundle_expr_flattened_1.tag
-                    connect _cast_bits_to_bundle_expr_flattened_1.body, bits(bits(i2.body, 2, 0), 2, 1)
-                    connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
                     ; connect different types:
                     ; lhs: SInt<1>
                     ; rhs: SInt<2>
-                    connect __connect_variant_body_2, asSInt(bits(_cast_bits_to_bundle_expr_1.body, 1, 0)) @[module-XXXXXXXXXX.rs 8:1]
+                    connect __connect_variant_body_2, asSInt(bits(_cast_bits_to_bundle_expr.body, 1, 0)) @[module-XXXXXXXXXX.rs 8:1]
                     wire _bundle_literal_expr_2: Ty2
                     connect _bundle_literal_expr_2.tag, UInt<1>(0h1)
                     connect _bundle_literal_expr_2.body, asUInt(__connect_variant_body_2)
@@ -4159,13 +4145,13 @@ circuit check_enum_connect_any:
                 connect o1, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 8:1]
             else:
                 wire __connect_variant_body_3: Ty4 @[module-XXXXXXXXXX.rs 8:1]
-                wire _cast_bits_to_bundle_expr_2: Ty4
+                wire _cast_bits_to_bundle_expr_1: Ty4
-                wire _cast_bits_to_bundle_expr_flattened_2: Ty4
+                wire _cast_bits_to_bundle_expr_flattened_1: Ty4
-                connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(bits(i2.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(bits(i2.body, 0, 0), 0, 0)
-                connect _cast_bits_to_bundle_expr_2.tag, _cast_bits_to_bundle_expr_flattened_2.tag
+                connect _cast_bits_to_bundle_expr_1.tag, _cast_bits_to_bundle_expr_flattened_1.tag
-                connect _cast_bits_to_bundle_expr_flattened_2.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_flattened_1.body, UInt<0>(0)
-                connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
+                connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
-                connect __connect_variant_body_3, _cast_bits_to_bundle_expr_2 @[module-XXXXXXXXXX.rs 8:1]
+                connect __connect_variant_body_3, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 8:1]
                 wire _bundle_literal_expr_4: Ty0
                 connect _bundle_literal_expr_4.tag, UInt<2>(0h2)
                 wire _cast_bundle_to_bits_expr_1: Ty4
@@ -4187,29 +4173,23 @@ circuit check_enum_connect_any:
                 connect o2, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 9:1]
             else when eq(i1.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 9:1]
                 wire __connect_variant_body_5: Ty3 @[module-XXXXXXXXXX.rs 9:1]
-                wire _cast_bits_to_bundle_expr_3: Ty2
+                wire _cast_bits_to_bundle_expr_2: Ty2
-                wire _cast_bits_to_bundle_expr_flattened_3: Ty2
+                wire _cast_bits_to_bundle_expr_flattened_2: Ty2
-                connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(bits(i1.body, 1, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(bits(i1.body, 1, 0), 0, 0)
-                connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_bundle_expr_flattened_3.tag
+                connect _cast_bits_to_bundle_expr_2.tag, _cast_bits_to_bundle_expr_flattened_2.tag
-                connect _cast_bits_to_bundle_expr_flattened_3.body, bits(bits(i1.body, 1, 0), 1, 1)
+                connect _cast_bits_to_bundle_expr_flattened_2.body, bits(bits(i1.body, 1, 0), 1, 1)
-                connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
+                connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
-                when eq(_cast_bits_to_bundle_expr_3.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 9:1]
+                when eq(_cast_bits_to_bundle_expr_2.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 9:1]
                     wire _bundle_literal_expr_6: Ty3
                     connect _bundle_literal_expr_6.tag, UInt<1>(0h0)
                     connect _bundle_literal_expr_6.body, UInt<2>(0h0)
                     connect __connect_variant_body_5, _bundle_literal_expr_6 @[module-XXXXXXXXXX.rs 9:1]
                 else:
                     wire __connect_variant_body_6: SInt<2> @[module-XXXXXXXXXX.rs 9:1]
-                    wire _cast_bits_to_bundle_expr_4: Ty2
-                    wire _cast_bits_to_bundle_expr_flattened_4: Ty2
-                    connect _cast_bits_to_bundle_expr_flattened_4.tag, bits(bits(i1.body, 1, 0), 0, 0)
-                    connect _cast_bits_to_bundle_expr_4.tag, _cast_bits_to_bundle_expr_flattened_4.tag
-                    connect _cast_bits_to_bundle_expr_flattened_4.body, bits(bits(i1.body, 1, 0), 1, 1)
-                    connect _cast_bits_to_bundle_expr_4.body, _cast_bits_to_bundle_expr_flattened_4.body
                     ; connect different types:
                     ; lhs: SInt<2>
                     ; rhs: SInt<1>
-                    connect __connect_variant_body_6, asSInt(bits(_cast_bits_to_bundle_expr_4.body, 0, 0)) @[module-XXXXXXXXXX.rs 9:1]
+                    connect __connect_variant_body_6, asSInt(bits(_cast_bits_to_bundle_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 9:1]
                     wire _bundle_literal_expr_7: Ty3
                     connect _bundle_literal_expr_7.tag, UInt<1>(0h1)
                     connect _bundle_literal_expr_7.body, asUInt(__connect_variant_body_6)
@@ -4225,13 +4205,13 @@ circuit check_enum_connect_any:
                 connect o2, _bundle_literal_expr_8 @[module-XXXXXXXXXX.rs 9:1]
             else:
                 wire __connect_variant_body_7: Ty4 @[module-XXXXXXXXXX.rs 9:1]
-                wire _cast_bits_to_bundle_expr_5: Ty4
+                wire _cast_bits_to_bundle_expr_3: Ty4
-                wire _cast_bits_to_bundle_expr_flattened_5: Ty4
+                wire _cast_bits_to_bundle_expr_flattened_3: Ty4
-                connect _cast_bits_to_bundle_expr_flattened_5.tag, bits(bits(i1.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(bits(i1.body, 0, 0), 0, 0)
-                connect _cast_bits_to_bundle_expr_5.tag, _cast_bits_to_bundle_expr_flattened_5.tag
+                connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_bundle_expr_flattened_3.tag
-                connect _cast_bits_to_bundle_expr_flattened_5.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_flattened_3.body, UInt<0>(0)
-                connect _cast_bits_to_bundle_expr_5.body, _cast_bits_to_bundle_expr_flattened_5.body
+                connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
-                connect __connect_variant_body_7, _cast_bits_to_bundle_expr_5 @[module-XXXXXXXXXX.rs 9:1]
+                connect __connect_variant_body_7, _cast_bits_to_bundle_expr_3 @[module-XXXXXXXXXX.rs 9:1]
                 wire _bundle_literal_expr_9: Ty1
                 connect _bundle_literal_expr_9.tag, UInt<2>(0h2)
                 wire _cast_bundle_to_bits_expr_3: Ty4
@@ -4883,34 +4863,20 @@ circuit check_struct_cmp_eq:
         input test_struct_3_rhs: Ty3 @[module-XXXXXXXXXX.rs 21:1]
         output test_struct_3_cmp_eq: UInt<1> @[module-XXXXXXXXXX.rs 22:1]
         output test_struct_3_cmp_ne: UInt<1> @[module-XXXXXXXXXX.rs 24:1]
-        wire _array_literal_expr: UInt<1>[3]
+        wire _bundle_structural_eq: UInt<1>
-        connect _array_literal_expr[0], eq(tuple_lhs.`0`, tuple_rhs.`0`)
+        connect _bundle_structural_eq, and(eq(tuple_lhs.`0`, tuple_rhs.`0`), eq(tuple_lhs.`1`, tuple_rhs.`1`))
-        connect _array_literal_expr[1], eq(tuple_lhs.`1`, tuple_rhs.`1`)
+        wire _bundle_structural_eq_1: UInt<1>
-        connect _array_literal_expr[2], eq(tuple_lhs.`2`, tuple_rhs.`2`)
+        connect _bundle_structural_eq_1, and(_bundle_structural_eq, eq(tuple_lhs.`2`, tuple_rhs.`2`))
-        wire _cast_array_to_bits_expr: UInt<1>[3]
+        connect tuple_cmp_eq, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 5:1]
-        connect _cast_array_to_bits_expr[0], _array_literal_expr[0]
+        connect tuple_cmp_ne, not(_bundle_structural_eq_1) @[module-XXXXXXXXXX.rs 7:1]
-        connect _cast_array_to_bits_expr[1], _array_literal_expr[1]
+        wire _bundle_structural_eq_2: UInt<1>
-        connect _cast_array_to_bits_expr[2], _array_literal_expr[2]
+        connect _bundle_structural_eq_2, and(eq(test_struct_lhs.a, test_struct_rhs.a), eq(test_struct_lhs.b, test_struct_rhs.b))
-        wire _cast_to_bits_expr: UInt<3>
+        connect test_struct_cmp_eq, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 11:1]
-        connect _cast_to_bits_expr, cat(_cast_array_to_bits_expr[2], cat(_cast_array_to_bits_expr[1], _cast_array_to_bits_expr[0]))
+        connect test_struct_cmp_ne, not(_bundle_structural_eq_2) @[module-XXXXXXXXXX.rs 13:1]
-        connect tuple_cmp_eq, andr(_cast_to_bits_expr) @[module-XXXXXXXXXX.rs 5:1]
-        wire _array_literal_expr_1: UInt<1>[3]
-        connect _array_literal_expr_1[0], neq(tuple_lhs.`0`, tuple_rhs.`0`)
-        connect _array_literal_expr_1[1], neq(tuple_lhs.`1`, tuple_rhs.`1`)
-        connect _array_literal_expr_1[2], neq(tuple_lhs.`2`, tuple_rhs.`2`)
-        wire _cast_array_to_bits_expr_1: UInt<1>[3]
-        connect _cast_array_to_bits_expr_1[0], _array_literal_expr_1[0]
-        connect _cast_array_to_bits_expr_1[1], _array_literal_expr_1[1]
-        connect _cast_array_to_bits_expr_1[2], _array_literal_expr_1[2]
-        wire _cast_to_bits_expr_1: UInt<3>
-        connect _cast_to_bits_expr_1, cat(_cast_array_to_bits_expr_1[2], cat(_cast_array_to_bits_expr_1[1], _cast_array_to_bits_expr_1[0]))
-        connect tuple_cmp_ne, orr(_cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 7:1]
-        connect test_struct_cmp_eq, and(eq(test_struct_lhs.a, test_struct_rhs.a), eq(test_struct_lhs.b, test_struct_rhs.b)) @[module-XXXXXXXXXX.rs 11:1]
-        connect test_struct_cmp_ne, or(neq(test_struct_lhs.a, test_struct_rhs.a), neq(test_struct_lhs.b, test_struct_rhs.b)) @[module-XXXXXXXXXX.rs 13:1]
         connect test_struct_2_cmp_eq, eq(test_struct_2_lhs.v, test_struct_2_rhs.v) @[module-XXXXXXXXXX.rs 17:1]
-        connect test_struct_2_cmp_ne, neq(test_struct_2_lhs.v, test_struct_2_rhs.v) @[module-XXXXXXXXXX.rs 19:1]
+        connect test_struct_2_cmp_ne, not(eq(test_struct_2_lhs.v, test_struct_2_rhs.v)) @[module-XXXXXXXXXX.rs 19:1]
         connect test_struct_3_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 23:1]
-        connect test_struct_3_cmp_ne, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 25:1]
+        connect test_struct_3_cmp_ne, not(UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 25:1]
 ",
     };
 }

crates/fayalite/tests/sim.rs

@@ -5,6 +5,7 @@ use bitvec::{order::Lsb0, view::BitView};
 use fayalite::{
     assert_export_firrtl,
     firrtl::ExportOptions,
+    formal::FormalInputKind,
     memory::{ReadStruct, ReadWriteStruct, WriteStruct, splat_mask},
     module::{
         instance_with_loc, memory_with_init_and_loc, reg_builder_with_loc,
@@ -16,7 +17,12 @@ use fayalite::{
     ty::SimValueDebug,
     util::{RcWriter, ready_valid::queue},
 };
-use std::{collections::BTreeMap, num::NonZeroUsize, rc::Rc};
+use std::{
+    collections::BTreeMap,
+    num::NonZeroUsize,
+    panic::{AssertUnwindSafe, catch_unwind, resume_unwind},
+    rc::Rc,
+};
 
 #[hdl_module(outline_generated)]
 pub fn connect_const() {
@@ -3610,3 +3616,200 @@ circuit sim_trace_as_string: %[[
 ",
     };
 }
+
+#[hdl_module(outline_generated)]
+pub fn formal_counter(count_modulus: u8, asserted_max_count: u8) {
+    #[hdl]
+    let cd = wire();
+    connect(
+        cd,
+        #[hdl]
+        ClockDomain {
+            clk: formal_global_clock(),
+            rst: formal_reset(),
+        },
+    );
+    #[hdl]
+    let count_reg: UInt<8> = reg_builder().clock_domain(cd).reset(0u8);
+    let next_count = count_reg + 1u8;
+    #[hdl]
+    if next_count.cmp_lt(count_modulus) {
+        connect_any(count_reg, next_count);
+    } else {
+        connect(count_reg, 0u8);
+    }
+    #[hdl]
+    let count: UInt<8> = m.output();
+    connect(count, count_reg);
+    #[hdl]
+    let enable_assert: Bool = m.input();
+    #[hdl]
+    if enable_assert {
+        hdl_assert(cd.clk, count_reg.cmp_le(asserted_max_count), "");
+    }
+    #[hdl]
+    let any_seq_out: UInt<16> = m.output();
+    connect(any_seq_out, any_seq(any_seq_out.ty()));
+}
+
+#[hdl]
+#[test]
+fn test_formal_counter() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let mut sim = Simulation::new(formal_counter(10, 10));
+    let _checked_vcd_output =
+        checked_vcd_output!(&mut sim, "tests/sim/expected/test_formal_counter.vcd");
+    let Some((_, any_seq_in)) = sim
+        .global_io()
+        .into_iter()
+        .find(|(global, _)| global.kind() == FormalInputKind::AnySeq)
+    else {
+        panic!("can't find any_seq");
+    };
+    let any_seq_in = Expr::<UInt<16>>::from_canonical(any_seq_in);
+    sim.write_clock(formal_global_clock(), false);
+    sim.write_reset(formal_reset(), true);
+    sim.write(any_seq_in, 0u16);
+    sim.write(sim.io().enable_assert, true);
+    sim.advance_time(SimDuration::from_micros(1));
+    assert_eq!(sim.read(sim.io().any_seq_out).as_int(), 0u16);
+    sim.write_clock(formal_global_clock(), true);
+    sim.write(any_seq_in, 1234u16);
+    assert_eq!(sim.read(sim.io().any_seq_out).as_int(), 1234u16);
+    assert_eq!(sim.read(sim.io().count).as_int(), 0);
+    sim.write_reset(formal_reset(), false);
+    sim.advance_time(SimDuration::from_micros(1));
+    for i in 0..32u8 {
+        assert_eq!(i % 10, sim.read(sim.io().count).as_int());
+        sim.write_clock(formal_global_clock(), false);
+        sim.advance_time(SimDuration::from_micros(1));
+        sim.write_clock(formal_global_clock(), true);
+        sim.advance_time(SimDuration::from_micros(1));
+    }
+    let sim_debug = format!("{sim:#?}");
+    println!("#######\n{sim_debug}\n#######");
+    if sim_debug != include_str!("sim/expected/test_formal_counter.txt") {
+        panic!();
+    }
+}
+
+#[cfg(panic = "unwind")]
+#[hdl]
+#[test]
+fn test_formal_counter_assert() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let mut sim = Simulation::new(formal_counter(10, 8));
+    let _checked_vcd_output = checked_vcd_output!(
+        &mut sim,
+        "tests/sim/expected/test_formal_counter_assert.vcd"
+    );
+    let Some((_, any_seq_in)) = sim
+        .global_io()
+        .into_iter()
+        .find(|(global, _)| global.kind() == FormalInputKind::AnySeq)
+    else {
+        panic!("can't find any_seq");
+    };
+    let any_seq_in = Expr::<UInt<16>>::from_canonical(any_seq_in);
+    let half_us = SimDuration::from_nanos(500);
+    sim.write_clock(formal_global_clock(), false);
+    sim.write_reset(formal_reset(), true);
+    sim.write(any_seq_in, 0u16);
+    sim.write(sim.io().enable_assert, false);
+    sim.advance_time(half_us);
+    assert_eq!(sim.read(sim.io().any_seq_out).as_int(), 0u16);
+    sim.write_clock(formal_global_clock(), true);
+    sim.write(any_seq_in, 1234u16);
+    assert_eq!(sim.read(sim.io().any_seq_out).as_int(), 1234u16);
+    assert_eq!(sim.read(sim.io().count).as_int(), 0);
+    sim.write_reset(formal_reset(), false);
+    sim.advance_time(half_us);
+    const PANIC_MSG: &str = "Assertions/Assumptions failed at time 20.500000000000 \u{3bc}s:\n\
+at module-XXXXXXXXXX.rs:12:1: in InstantiatedModule(formal_counter: formal_counter): assert failed: \n";
+    const EXPECTED_FAILURE_CYCLE: u8 = 19;
+    for i in 0.. {
+        dbg!(i);
+        assert_eq!(i % 10, sim.read(sim.io().count).as_int());
+        sim.write(sim.io().enable_assert, i > 15);
+        sim.write_clock(formal_global_clock(), false);
+        sim.advance_time(half_us);
+        match catch_unwind(AssertUnwindSafe(|| {
+            sim.write_clock(formal_global_clock(), true);
+            sim.advance_time(half_us);
+        })) {
+            Ok(()) => assert!(i < EXPECTED_FAILURE_CYCLE),
+            Err(e) => match e.downcast::<String>() {
+                Ok(e) if *e == PANIC_MSG => {
+                    assert_eq!(i, EXPECTED_FAILURE_CYCLE);
+                    break;
+                }
+                Ok(e) => resume_unwind(e),
+                Err(e) => resume_unwind(e),
+            },
+        }
+    }
+}
+
+#[hdl_module(outline_generated)]
+pub fn enum_structural_eq() {
+    #[hdl]
+    let a: HdlOption<UInt<2>> = m.input();
+    #[hdl]
+    let b: HdlOption<UInt<2>> = m.input();
+    #[hdl]
+    let eq: Bool = m.output();
+    #[hdl]
+    let structural_eq: Bool = m.output();
+    #[hdl]
+    let bit_eq: Bool = m.output();
+
+    connect(eq, a.cmp_eq(b));
+    // explicitly use StructuralEq (though cmp_eq also uses it above)
+    connect(
+        structural_eq,
+        fayalite::expr::ops::StructuralEq::new(Expr::canonical(a), Expr::canonical(b)),
+    );
+    connect(bit_eq, a.cast_to_bits().cmp_eq(b.cast_to_bits()));
+}
+
+#[test]
+fn test_enum_structural_eq() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let mut sim = Simulation::new(enum_structural_eq());
+    let _checked_vcd_output =
+        checked_vcd_output!(&mut sim, "tests/sim/expected/test_enum_structural_eq.vcd");
+    for a in 0..8u8 {
+        for b in 0..8u8 {
+            dbg!(a);
+            dbg!(b);
+            let a_sim_value = a.cast_to(UInt[3]).cast_bits_to(sim.io().a.ty());
+            let b_sim_value = b.cast_to(UInt[3]).cast_bits_to(sim.io().b.ty());
+            dbg!(&a_sim_value);
+            dbg!(&b_sim_value);
+            sim.write(sim.io().a, a_sim_value);
+            sim.write(sim.io().b, b_sim_value);
+            let a_with_zeroed_padding = if (a & 1) != 0 { a } else { 0 };
+            let b_with_zeroed_padding = if (b & 1) != 0 { b } else { 0 };
+            dbg!(a_with_zeroed_padding);
+            dbg!(b_with_zeroed_padding);
+            let expected_eq = a_with_zeroed_padding == b_with_zeroed_padding;
+            let expected_structural_eq = a_with_zeroed_padding == b_with_zeroed_padding;
+            let expected_bit_eq = a == b;
+            dbg!(expected_eq);
+            dbg!(expected_structural_eq);
+            dbg!(expected_bit_eq);
+            sim.advance_time(SimDuration::from_micros(1));
+            assert_eq!(sim.read_bool(sim.io().eq), expected_eq);
+            assert_eq!(
+                sim.read_bool(sim.io().structural_eq),
+                expected_structural_eq
+            );
+            assert_eq!(sim.read_bool(sim.io().bit_eq), expected_bit_eq);
+        }
+    }
+    let sim_debug = format!("{sim:#?}");
+    println!("#######\n{sim_debug}\n#######");
+    if sim_debug != include_str!("sim/expected/test_enum_structural_eq.txt") {
+        panic!();
+    }
+}

crates/fayalite/tests/sim/expected/array_rw.txt

@@ -419,6 +419,7 @@ Simulation {
         },
         pc: 38,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -497,6 +498,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1759,5 +1761,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/conditional_assignment_last.txt

@@ -76,6 +76,7 @@ Simulation {
         },
         pc: 5,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -101,6 +102,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -186,5 +188,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/connect_const.txt

@@ -54,6 +54,7 @@ Simulation {
         },
         pc: 2,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -77,6 +78,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -138,5 +140,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/connect_const_reset.txt

@@ -80,6 +80,7 @@ Simulation {
         },
         pc: 5,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -106,6 +107,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -206,5 +208,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/counter_async.txt

@@ -180,6 +180,7 @@ Simulation {
         },
         pc: 19,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -216,6 +217,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -385,5 +387,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/counter_sync.txt

@@ -162,6 +162,7 @@ Simulation {
         },
         pc: 16,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -197,6 +198,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -366,5 +368,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/duplicate_names.txt

@@ -72,6 +72,7 @@ Simulation {
         },
         pc: 4,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -97,6 +98,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [],
         uninitialized_ios: {},
@@ -169,5 +171,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/enum_with_simple_body.txt

@@ -409,6 +409,7 @@ Simulation {
         },
         pc: 45,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -465,6 +466,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -745,5 +747,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/enums.txt

@@ -1184,6 +1184,7 @@ Simulation {
         },
         pc: 133,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -1324,6 +1325,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1955,5 +1957,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/extern_module.txt

@@ -44,6 +44,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -67,6 +68,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -261,5 +263,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/extern_module2.txt

@@ -48,6 +48,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -72,6 +73,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -416,5 +418,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/last_connect.txt

@@ -407,6 +407,7 @@ Simulation {
         },
         pc: 44,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -464,6 +465,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -705,5 +707,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/many_memories.txt

@@ -2728,6 +2728,7 @@ Simulation {
         },
         pc: 256,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -3183,6 +3184,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -7927,5 +7929,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/memories.txt

@@ -494,6 +494,7 @@ Simulation {
         },
         pc: 41,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -579,6 +580,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1650,5 +1652,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/memories2.txt

@@ -526,6 +526,7 @@ Simulation {
         },
         pc: 52,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -607,6 +608,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1285,5 +1287,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/memories3.txt

@@ -1336,6 +1336,7 @@ Simulation {
         },
         pc: 129,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1495,6 +1496,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -3345,5 +3347,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/mod1.txt

@@ -187,6 +187,7 @@ Simulation {
         },
         pc: 17,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -225,6 +226,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -577,5 +579,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/phantom_const.txt

@@ -172,6 +172,7 @@ Simulation {
         },
         pc: 16,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -215,6 +216,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -527,5 +529,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_1_false_false.txt

@@ -1083,6 +1083,7 @@ Simulation {
         },
         pc: 134,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1201,6 +1202,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2160,5 +2162,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_1_false_true.txt

@@ -1064,6 +1064,7 @@ Simulation {
         },
         pc: 132,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1180,6 +1181,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2139,5 +2141,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_1_true_false.txt

@@ -1093,6 +1093,7 @@ Simulation {
         },
         pc: 136,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1211,6 +1212,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2170,5 +2172,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_1_true_true.txt

@@ -1074,6 +1074,7 @@ Simulation {
         },
         pc: 134,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1190,6 +1191,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2149,5 +2151,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_2_false_false.txt

@@ -1098,6 +1098,7 @@ Simulation {
         },
         pc: 135,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1219,6 +1220,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2178,5 +2180,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_2_false_true.txt

@@ -1079,6 +1079,7 @@ Simulation {
         },
         pc: 133,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1198,6 +1199,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2157,5 +2159,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_2_true_false.txt

@@ -1108,6 +1108,7 @@ Simulation {
         },
         pc: 137,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1229,6 +1230,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2188,5 +2190,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_2_true_true.txt

@@ -1089,6 +1089,7 @@ Simulation {
         },
         pc: 135,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1208,6 +1209,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2167,5 +2169,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_3_false_false.txt

@@ -1125,6 +1125,7 @@ Simulation {
         },
         pc: 139,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1248,6 +1249,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2187,5 +2189,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_3_false_true.txt

@@ -1106,6 +1106,7 @@ Simulation {
         },
         pc: 137,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1227,6 +1228,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2166,5 +2168,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_3_true_false.txt

@@ -1135,6 +1135,7 @@ Simulation {
         },
         pc: 141,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1258,6 +1259,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2197,5 +2199,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_3_true_true.txt

@@ -1116,6 +1116,7 @@ Simulation {
         },
         pc: 139,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1237,6 +1238,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2176,5 +2178,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_4_false_false.txt

@@ -1104,6 +1104,7 @@ Simulation {
         },
         pc: 135,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1227,6 +1228,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2186,5 +2188,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_4_false_true.txt

@@ -1085,6 +1085,7 @@ Simulation {
         },
         pc: 133,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1206,6 +1207,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2165,5 +2167,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_4_true_false.txt

@@ -1114,6 +1114,7 @@ Simulation {
         },
         pc: 137,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1237,6 +1238,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2196,5 +2198,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/queue_4_true_true.txt

@@ -1095,6 +1095,7 @@ Simulation {
         },
         pc: 135,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -1216,6 +1217,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2175,5 +2177,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/ripple_counter.txt

@@ -636,6 +636,7 @@ Simulation {
         },
         pc: 69,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -725,6 +726,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1790,5 +1792,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/shift_register.txt

@@ -254,6 +254,7 @@ Simulation {
         },
         pc: 34,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -293,6 +294,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -545,5 +547,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_fork_join.txt

@@ -60,6 +60,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -87,6 +88,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -521,5 +523,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_fork_join_scope.txt

@@ -60,6 +60,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -87,6 +88,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -521,5 +523,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_only_connects.txt

@@ -375,6 +375,7 @@ Simulation {
         },
         pc: 41,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -475,6 +476,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -1768,5 +1770,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_read_past.txt

@@ -512,6 +512,7 @@ Simulation {
         },
         pc: 57,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -591,6 +592,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -9726,5 +9728,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_resettable_counter_async.txt

@@ -48,6 +48,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -72,6 +73,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -539,5 +541,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_resettable_counter_async_immediate_reset.txt

@@ -48,6 +48,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -72,6 +73,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -539,5 +541,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_resettable_counter_sync.txt

@@ -48,6 +48,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -72,6 +73,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -497,5 +499,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_resettable_counter_sync_immediate_reset.txt

@@ -48,6 +48,7 @@ Simulation {
         },
         pc: 0,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [],
         },
@@ -72,6 +73,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -497,5 +499,6 @@ Simulation {
             },
         ),
     },
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/sim_trace_as_string.txt

@@ -494,6 +494,7 @@ Simulation {
         },
         pc: 43,
         memory_write_log: [],
+        assert_failed_log: [],
         memories: StatePart {
             value: [
                 MemoryData {
@@ -570,6 +571,7 @@ Simulation {
             ..
         },
     },
+    global_io: {},
     main_module: SimulationModuleState {
         base_targets: [
             Instance {
@@ -2250,5 +2252,6 @@ Simulation {
     }),
     waiting_sensitivity_sets_by_address: {},
     waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
     ..
 }

crates/fayalite/tests/sim/expected/test_enum_structural_eq.txt

@@ -0,0 +1,522 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 2,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "",
+                                ty: Enum {
+                                    HdlNone,
+                                    HdlSome,
+                                },
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Enum {
+                                    HdlNone,
+                                    HdlSome,
+                                },
+                            },
+                        ],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 13,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::a",
+                                ty: Enum {
+                                    HdlNone,
+                                    HdlSome(UInt<2>),
+                                },
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<3>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::b",
+                                ty: Enum {
+                                    HdlNone,
+                                    HdlSome(UInt<2>),
+                                },
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<3>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<2>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::eq",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::structural_eq",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::bit_eq",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(10), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    value: 0x1,
+                },
+                1: Const {
+                    dest: StatePartIndex<BigSlots>(9), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    value: 0x0,
+                },
+                2: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                    src: StatePartIndex<BigSlots>(3), // (0x7) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::b", ty: Enum {HdlNone, HdlSome(UInt<2>)} },
+                },
+                3: SliceInt {
+                    dest: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<2> },
+                    src: StatePartIndex<BigSlots>(4), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                    start: 1,
+                    len: 2,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                4: AndBigWithSmallImmediate {
+                    dest: StatePartIndex<SmallSlots>(1), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    lhs: StatePartIndex<BigSlots>(3), // (0x7) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::b", ty: Enum {HdlNone, HdlSome(UInt<2>)} },
+                    rhs: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                5: Copy {
+                    dest: StatePartIndex<BigSlots>(1), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                    src: StatePartIndex<BigSlots>(0), // (0x7) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::a", ty: Enum {HdlNone, HdlSome(UInt<2>)} },
+                },
+                6: SliceInt {
+                    dest: StatePartIndex<BigSlots>(2), // (0x3) SlotDebugData { name: "", ty: UInt<2> },
+                    src: StatePartIndex<BigSlots>(1), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                    start: 1,
+                    len: 2,
+                },
+                7: CmpEq {
+                    dest: StatePartIndex<BigSlots>(11), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(2), // (0x3) SlotDebugData { name: "", ty: UInt<2> },
+                    rhs: StatePartIndex<BigSlots>(5), // (0x3) SlotDebugData { name: "", ty: UInt<2> },
+                },
+                8: CmpEq {
+                    dest: StatePartIndex<BigSlots>(12), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(1), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                    rhs: StatePartIndex<BigSlots>(4), // (0x7) SlotDebugData { name: "", ty: UInt<3> },
+                },
+                // at: module-XXXXXXXXXX.rs:9:1
+                9: Copy {
+                    dest: StatePartIndex<BigSlots>(8), // (0x1) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::bit_eq", ty: Bool },
+                    src: StatePartIndex<BigSlots>(12), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:2:1
+                10: AndBigWithSmallImmediate {
+                    dest: StatePartIndex<SmallSlots>(0), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    lhs: StatePartIndex<BigSlots>(0), // (0x7) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::a", ty: Enum {HdlNone, HdlSome(UInt<2>)} },
+                    rhs: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                11: BranchIfSmallNeImmediate {
+                    target: 14,
+                    lhs: StatePartIndex<SmallSlots>(0), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    rhs: 0x0,
+                },
+                12: BranchIfSmallNeImmediate {
+                    target: 14,
+                    lhs: StatePartIndex<SmallSlots>(1), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    rhs: 0x0,
+                },
+                13: Copy {
+                    dest: StatePartIndex<BigSlots>(9), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(10), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                14: BranchIfSmallNeImmediate {
+                    target: 17,
+                    lhs: StatePartIndex<SmallSlots>(0), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    rhs: 0x1,
+                },
+                15: BranchIfSmallNeImmediate {
+                    target: 17,
+                    lhs: StatePartIndex<SmallSlots>(1), // (0x1 1) SlotDebugData { name: "", ty: Enum {HdlNone, HdlSome} },
+                    rhs: 0x1,
+                },
+                16: Copy {
+                    dest: StatePartIndex<BigSlots>(9), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(11), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:7:1
+                17: Copy {
+                    dest: StatePartIndex<BigSlots>(6), // (0x1) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::eq", ty: Bool },
+                    src: StatePartIndex<BigSlots>(9), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:8:1
+                18: Copy {
+                    dest: StatePartIndex<BigSlots>(7), // (0x1) SlotDebugData { name: "InstantiatedModule(enum_structural_eq: enum_structural_eq).enum_structural_eq::structural_eq", ty: Bool },
+                    src: StatePartIndex<BigSlots>(9), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                19: Return,
+            ],
+            ..
+        },
+        pc: 19,
+        memory_write_log: [],
+        assert_failed_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [
+                1,
+                1,
+            ],
+        },
+        big_slots: StatePart {
+            value: [
+                7,
+                7,
+                3,
+                7,
+                7,
+                3,
+                1,
+                1,
+                1,
+                1,
+                1,
+                1,
+                1,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::enum_structural_eq,
+        instantiated: Module {
+            name: enum_structural_eq,
+            ..
+        },
+    },
+    global_io: {},
+    main_module: SimulationModuleState {
+        base_targets: [
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.a,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.b,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.eq,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.structural_eq,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.bit_eq,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.a,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.b,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.bit_eq,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.eq,
+            Instance {
+                name: <simulator>::enum_structural_eq,
+                instantiated: Module {
+                    name: enum_structural_eq,
+                    ..
+                },
+            }.structural_eq,
+        },
+        did_initial_settle: true,
+        clocks_for_past: {},
+    },
+    extern_modules: [],
+    trace_decls: TraceModule {
+        name: "enum_structural_eq",
+        children: [
+            TraceModuleIO {
+                name: "a",
+                child: TraceEnumWithFields {
+                    name: "a",
+                    discriminant: TraceEnumDiscriminant {
+                        location: TraceScalarId(0),
+                        name: "$tag",
+                        ty: Enum {
+                            HdlNone,
+                            HdlSome(UInt<2>),
+                        },
+                        flow: Source,
+                    },
+                    non_empty_fields: [
+                        TraceUInt {
+                            location: TraceScalarId(1),
+                            name: "HdlSome",
+                            ty: UInt<2>,
+                            flow: Source,
+                        },
+                    ],
+                    ty: Enum {
+                        HdlNone,
+                        HdlSome(UInt<2>),
+                    },
+                    flow: Source,
+                },
+                ty: Enum {
+                    HdlNone,
+                    HdlSome(UInt<2>),
+                },
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "b",
+                child: TraceEnumWithFields {
+                    name: "b",
+                    discriminant: TraceEnumDiscriminant {
+                        location: TraceScalarId(2),
+                        name: "$tag",
+                        ty: Enum {
+                            HdlNone,
+                            HdlSome(UInt<2>),
+                        },
+                        flow: Source,
+                    },
+                    non_empty_fields: [
+                        TraceUInt {
+                            location: TraceScalarId(3),
+                            name: "HdlSome",
+                            ty: UInt<2>,
+                            flow: Source,
+                        },
+                    ],
+                    ty: Enum {
+                        HdlNone,
+                        HdlSome(UInt<2>),
+                    },
+                    flow: Source,
+                },
+                ty: Enum {
+                    HdlNone,
+                    HdlSome(UInt<2>),
+                },
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "eq",
+                child: TraceBool {
+                    location: TraceScalarId(4),
+                    name: "eq",
+                    flow: Sink,
+                },
+                ty: Bool,
+                flow: Sink,
+            },
+            TraceModuleIO {
+                name: "structural_eq",
+                child: TraceBool {
+                    location: TraceScalarId(5),
+                    name: "structural_eq",
+                    flow: Sink,
+                },
+                ty: Bool,
+                flow: Sink,
+            },
+            TraceModuleIO {
+                name: "bit_eq",
+                child: TraceBool {
+                    location: TraceScalarId(6),
+                    name: "bit_eq",
+                    flow: Sink,
+                },
+                ty: Bool,
+                flow: Sink,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: EnumDiscriminant {
+                index: StatePartIndex<SmallSlots>(0),
+                ty: Enum {
+                    HdlNone,
+                    HdlSome(UInt<2>),
+                },
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<2>,
+            },
+            maybe_changed: true,
+            state: 0x3,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: EnumDiscriminant {
+                index: StatePartIndex<SmallSlots>(1),
+                ty: Enum {
+                    HdlNone,
+                    HdlSome(UInt<2>),
+                },
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(3),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(5),
+                ty: UInt<2>,
+            },
+            maybe_changed: true,
+            state: 0x3,
+            last_state: 0x3,
+        },
+        SimTrace {
+            id: TraceScalarId(4),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(6),
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(5),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(7),
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(6),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(8),
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    clocks_triggered: [],
+    event_queue: EventQueue(EventQueueData {
+        instant: 64 μs,
+        events: {},
+    }),
+    waiting_sensitivity_sets_by_address: {},
+    waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [],
+    ..
+}

crates/fayalite/tests/sim/expected/test_enum_structural_eq.vcd

@@ -0,0 +1,282 @@
+$timescale 1 ps $end
+$scope module enum_structural_eq $end
+$scope struct a $end
+$var string 1 +LxwI \$tag $end
+$var wire 2 {bf!u HdlSome $end
+$upscope $end
+$scope struct b $end
+$var string 1 O%@#" \$tag $end
+$var wire 2 ]xpB, HdlSome $end
+$upscope $end
+$var wire 1 Yp4xI eq $end
+$var wire 1 >R/<6 structural_eq $end
+$var wire 1 ,}=e] bit_eq $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+sHdlNone\x20(0) +LxwI
+b0 {bf!u
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+1Yp4xI
+1>R/<6
+1,}=e]
+$end
+#1000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+0,}=e]
+#2000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+1Yp4xI
+1>R/<6
+#3000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#4000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+1Yp4xI
+1>R/<6
+#5000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#6000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+1Yp4xI
+1>R/<6
+#7000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#8000000
+sHdlSome\x20(1) +LxwI
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+#9000000
+sHdlSome\x20(1) O%@#"
+1Yp4xI
+1>R/<6
+1,}=e]
+#10000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+0Yp4xI
+0>R/<6
+0,}=e]
+#11000000
+sHdlSome\x20(1) O%@#"
+#12000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+#13000000
+sHdlSome\x20(1) O%@#"
+#14000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+#15000000
+sHdlSome\x20(1) O%@#"
+#16000000
+sHdlNone\x20(0) +LxwI
+b1 {bf!u
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+1Yp4xI
+1>R/<6
+#17000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#18000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+1Yp4xI
+1>R/<6
+1,}=e]
+#19000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+0,}=e]
+#20000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+1Yp4xI
+1>R/<6
+#21000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#22000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+1Yp4xI
+1>R/<6
+#23000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#24000000
+sHdlSome\x20(1) +LxwI
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+#25000000
+sHdlSome\x20(1) O%@#"
+#26000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+#27000000
+sHdlSome\x20(1) O%@#"
+1Yp4xI
+1>R/<6
+1,}=e]
+#28000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+0Yp4xI
+0>R/<6
+0,}=e]
+#29000000
+sHdlSome\x20(1) O%@#"
+#30000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+#31000000
+sHdlSome\x20(1) O%@#"
+#32000000
+sHdlNone\x20(0) +LxwI
+b10 {bf!u
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+1Yp4xI
+1>R/<6
+#33000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#34000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+1Yp4xI
+1>R/<6
+#35000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#36000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+1Yp4xI
+1>R/<6
+1,}=e]
+#37000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+0,}=e]
+#38000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+1Yp4xI
+1>R/<6
+#39000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#40000000
+sHdlSome\x20(1) +LxwI
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+#41000000
+sHdlSome\x20(1) O%@#"
+#42000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+#43000000
+sHdlSome\x20(1) O%@#"
+#44000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+#45000000
+sHdlSome\x20(1) O%@#"
+1Yp4xI
+1>R/<6
+1,}=e]
+#46000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+0Yp4xI
+0>R/<6
+0,}=e]
+#47000000
+sHdlSome\x20(1) O%@#"
+#48000000
+sHdlNone\x20(0) +LxwI
+b11 {bf!u
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+1Yp4xI
+1>R/<6
+#49000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#50000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+1Yp4xI
+1>R/<6
+#51000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#52000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+1Yp4xI
+1>R/<6
+#53000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+#54000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+1Yp4xI
+1>R/<6
+1,}=e]
+#55000000
+sHdlSome\x20(1) O%@#"
+0Yp4xI
+0>R/<6
+0,}=e]
+#56000000
+sHdlSome\x20(1) +LxwI
+sHdlNone\x20(0) O%@#"
+b0 ]xpB,
+#57000000
+sHdlSome\x20(1) O%@#"
+#58000000
+sHdlNone\x20(0) O%@#"
+b1 ]xpB,
+#59000000
+sHdlSome\x20(1) O%@#"
+#60000000
+sHdlNone\x20(0) O%@#"
+b10 ]xpB,
+#61000000
+sHdlSome\x20(1) O%@#"
+#62000000
+sHdlNone\x20(0) O%@#"
+b11 ]xpB,
+#63000000
+sHdlSome\x20(1) O%@#"
+1Yp4xI
+1>R/<6
+1,}=e]
+#64000000

crates/fayalite/tests/sim/expected/test_formal_counter.txt

@@ -0,0 +1,855 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 5,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                        ],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 26,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::enable_assert",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::any_seq_out",
+                                ty: UInt<16>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.clk",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.rst",
+                                ty: SyncReset,
+                            },
+                            SlotDebugData {
+                                name: ".clk",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: ".rst",
+                                ty: SyncReset,
+                            },
+                            SlotDebugData {
+                                name: "<<Global>>::formal_global_clock",
+                                ty: Clock,
+                            },
+                            SlotDebugData {
+                                name: "<<Global>>::formal_reset",
+                                ty: SyncReset,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg$next",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<9>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: Bool,
+                            },
+                            SlotDebugData {
+                                name: "<<Global>>::any_seq",
+                                ty: UInt<16>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:15:1
+                0: Copy {
+                    dest: StatePartIndex<BigSlots>(2), // (0x4d2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::any_seq_out", ty: UInt<16> },
+                    src: StatePartIndex<BigSlots>(25), // (0x4d2) SlotDebugData { name: "<<Global>>::any_seq", ty: UInt<16> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(19), // (0x0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(8), // (0x0) SlotDebugData { name: "<<Global>>::formal_reset", ty: SyncReset },
+                },
+                2: NotU {
+                    dest: StatePartIndex<BigSlots>(20), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(19), // (0x0) SlotDebugData { name: "", ty: Bool },
+                    width: 1,
+                },
+                3: Const {
+                    dest: StatePartIndex<BigSlots>(18), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    value: 0x1,
+                },
+                4: And {
+                    dest: StatePartIndex<BigSlots>(21), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(18), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    rhs: StatePartIndex<BigSlots>(20), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                5: NotU {
+                    dest: StatePartIndex<BigSlots>(22), // (0x0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(21), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    width: 1,
+                },
+                // at: module-XXXXXXXXXX.rs:12:1
+                6: Copy {
+                    dest: StatePartIndex<BigSlots>(24), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(18), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:9:1
+                7: Copy {
+                    dest: StatePartIndex<BigSlots>(0), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                8: Const {
+                    dest: StatePartIndex<BigSlots>(14), // (0xa) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0xa,
+                },
+                9: CmpLe {
+                    dest: StatePartIndex<BigSlots>(17), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                    rhs: StatePartIndex<BigSlots>(14), // (0xa) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                10: Or {
+                    dest: StatePartIndex<BigSlots>(23), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(17), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    rhs: StatePartIndex<BigSlots>(22), // (0x0) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:11:1
+                11: BranchIfZero {
+                    target: 13,
+                    value: StatePartIndex<BigSlots>(1), // (0x1) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::enable_assert", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:12:1
+                12: Copy {
+                    dest: StatePartIndex<BigSlots>(24), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(23), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                13: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(4), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(24), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                14: Const {
+                    dest: StatePartIndex<BigSlots>(12), // (0x1) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x1,
+                },
+                15: Add {
+                    dest: StatePartIndex<BigSlots>(13), // (0x3) SlotDebugData { name: "", ty: UInt<9> },
+                    lhs: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                    rhs: StatePartIndex<BigSlots>(12), // (0x1) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                16: CmpLt {
+                    dest: StatePartIndex<BigSlots>(15), // (0x1) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<BigSlots>(13), // (0x3) SlotDebugData { name: "", ty: UInt<9> },
+                    rhs: StatePartIndex<BigSlots>(14), // (0xa) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                17: CastToUInt {
+                    dest: StatePartIndex<BigSlots>(16), // (0x3) SlotDebugData { name: "", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(13), // (0x3) SlotDebugData { name: "", ty: UInt<9> },
+                    dest_width: 8,
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                18: Copy {
+                    dest: StatePartIndex<BigSlots>(10), // (0x3) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg$next", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                19: BranchIfZero {
+                    target: 21,
+                    value: StatePartIndex<BigSlots>(15), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:6:1
+                20: Copy {
+                    dest: StatePartIndex<BigSlots>(10), // (0x3) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg$next", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(16), // (0x3) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                21: Const {
+                    dest: StatePartIndex<BigSlots>(11), // (0x0) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x0,
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                22: BranchIfNonZero {
+                    target: 24,
+                    value: StatePartIndex<BigSlots>(15), // (0x1) SlotDebugData { name: "", ty: Bool },
+                },
+                // at: module-XXXXXXXXXX.rs:7:1
+                23: Copy {
+                    dest: StatePartIndex<BigSlots>(10), // (0x3) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg$next", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(11), // (0x0) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                24: Copy {
+                    dest: StatePartIndex<BigSlots>(5), // (0x1) SlotDebugData { name: ".clk", ty: Clock },
+                    src: StatePartIndex<BigSlots>(7), // (0x1) SlotDebugData { name: "<<Global>>::formal_global_clock", ty: Clock },
+                },
+                25: Copy {
+                    dest: StatePartIndex<BigSlots>(6), // (0x0) SlotDebugData { name: ".rst", ty: SyncReset },
+                    src: StatePartIndex<BigSlots>(8), // (0x0) SlotDebugData { name: "<<Global>>::formal_reset", ty: SyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                26: Copy {
+                    dest: StatePartIndex<BigSlots>(3), // (0x1) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.clk", ty: Clock },
+                    src: StatePartIndex<BigSlots>(5), // (0x1) SlotDebugData { name: ".clk", ty: Clock },
+                },
+                27: Copy {
+                    dest: StatePartIndex<BigSlots>(4), // (0x0) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.rst", ty: SyncReset },
+                    src: StatePartIndex<BigSlots>(6), // (0x0) SlotDebugData { name: ".rst", ty: SyncReset },
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                28: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(3), // (0x1) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.clk", ty: Clock },
+                },
+                29: AndSmall {
+                    dest: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                30: IsNonZeroDestIsSmall {
+                    dest: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    src: StatePartIndex<BigSlots>(4), // (0x0) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::cd.rst", ty: SyncReset },
+                },
+                31: BranchIfSmallZero {
+                    target: 36,
+                    value: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                32: BranchIfSmallNonZero {
+                    target: 35,
+                    value: StatePartIndex<SmallSlots>(3), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                },
+                33: Copy {
+                    dest: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(10), // (0x3) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg$next", ty: UInt<8> },
+                },
+                34: Branch {
+                    target: 36,
+                },
+                35: Copy {
+                    dest: StatePartIndex<BigSlots>(9), // (0x2) SlotDebugData { name: "InstantiatedModule(formal_counter: formal_counter).formal_counter::count_reg", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(11), // (0x0) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:12:1
+                36: Assert {
+                    clk_triggered: StatePartIndex<SmallSlots>(1), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    pred: StatePartIndex<SmallSlots>(4), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    assert_index: 0,
+                },
+                // at: module-XXXXXXXXXX.rs:4:1
+                37: XorSmallImmediate {
+                    dest: StatePartIndex<SmallSlots>(0), // (0x0 0) SlotDebugData { name: "", ty: Bool },
+                    lhs: StatePartIndex<SmallSlots>(2), // (0x1 1) SlotDebugData { name: "", ty: Bool },
+                    rhs: 0x1,
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                38: Return,
+            ],
+            ..
+        },
+        pc: 38,
+        memory_write_log: [],
+        assert_failed_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [
+                0,
+                0,
+                1,
+                0,
+                1,
+            ],
+        },
+        big_slots: StatePart {
+            value: [
+                2,
+                1,
+                1234,
+                1,
+                0,
+                1,
+                0,
+                1,
+                0,
+                2,
+                3,
+                0,
+                1,
+                3,
+                10,
+                1,
+                3,
+                1,
+                1,
+                0,
+                1,
+                1,
+                0,
+                1,
+                1,
+                1234,
+            ],
+        },
+        sim_only_slots: StatePart {
+            value: [],
+        },
+    },
+    io: Instance {
+        name: <simulator>::formal_counter,
+        instantiated: Module {
+            name: formal_counter,
+            ..
+        },
+    },
+    global_io: {
+        SimIoForGlobal(
+            formal_global_clock,
+        ): CompiledValue {
+            layout: CompiledTypeLayout {
+                ty: Clock,
+                layout: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 1,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "<<Global>>::formal_global_clock",
+                                ty: Clock,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                body: Scalar,
+            },
+            range: TypeIndexRange {
+                small_slots: StatePartIndexRange<SmallSlots> { start: 0, len: 0 },
+                big_slots: StatePartIndexRange<BigSlots> { start: 7, len: 1 },
+                sim_only_slots: StatePartIndexRange<SimOnlySlots> { start: 0, len: 0 },
+            },
+            write: None,
+        },
+        SimIoForGlobal(
+            formal_reset,
+        ): CompiledValue {
+            layout: CompiledTypeLayout {
+                ty: SyncReset,
+                layout: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 1,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "<<Global>>::formal_reset",
+                                ty: SyncReset,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                body: Scalar,
+            },
+            range: TypeIndexRange {
+                small_slots: StatePartIndexRange<SmallSlots> { start: 0, len: 0 },
+                big_slots: StatePartIndexRange<BigSlots> { start: 8, len: 1 },
+                sim_only_slots: StatePartIndexRange<SimOnlySlots> { start: 0, len: 0 },
+            },
+            write: None,
+        },
+        SimIoForGlobal(
+            any_seq(
+                UInt<16>,
+            ),
+        ): CompiledValue {
+            layout: CompiledTypeLayout {
+                ty: UInt<16>,
+                layout: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 1,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "<<Global>>::any_seq",
+                                ty: UInt<16>,
+                            },
+                        ],
+                        ..
+                    },
+                    sim_only_slots: StatePartLayout<SimOnlySlots> {
+                        len: 0,
+                        debug_data: [],
+                        layout_data: [],
+                        ..
+                    },
+                },
+                body: Scalar,
+            },
+            range: TypeIndexRange {
+                small_slots: StatePartIndexRange<SmallSlots> { start: 5, len: 0 },
+                big_slots: StatePartIndexRange<BigSlots> { start: 25, len: 1 },
+                sim_only_slots: StatePartIndexRange<SimOnlySlots> { start: 0, len: 0 },
+            },
+            write: None,
+        },
+    },
+    main_module: SimulationModuleState {
+        base_targets: [
+            SimIoForGlobal(
+                formal_global_clock,
+            ),
+            SimIoForGlobal(
+                formal_reset,
+            ),
+            SimIoForGlobal(
+                any_seq(
+                    UInt<16>,
+                ),
+            ),
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.count,
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.enable_assert,
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.any_seq_out,
+        ],
+        uninitialized_ios: {},
+        io_targets: {
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.any_seq_out,
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.count,
+            Instance {
+                name: <simulator>::formal_counter,
+                instantiated: Module {
+                    name: formal_counter,
+                    ..
+                },
+            }.enable_assert,
+            SimIoForGlobal(
+                any_seq(
+                    UInt<16>,
+                ),
+            ),
+            SimIoForGlobal(
+                formal_global_clock,
+            ),
+            SimIoForGlobal(
+                formal_reset,
+            ),
+        },
+        did_initial_settle: true,
+        clocks_for_past: {},
+    },
+    extern_modules: [],
+    trace_decls: TraceModule {
+        name: "formal_counter",
+        children: [
+            TraceFormalInput {
+                name: "formal_global_clock",
+                child: TraceClock {
+                    location: TraceScalarId(5),
+                    name: "formal_global_clock",
+                    flow: Source,
+                },
+                formal_input: formal_global_clock,
+            },
+            TraceFormalInput {
+                name: "formal_reset",
+                child: TraceSyncReset {
+                    location: TraceScalarId(6),
+                    name: "formal_reset",
+                    flow: Source,
+                },
+                formal_input: formal_reset,
+            },
+            TraceFormalInput {
+                name: "any_seq",
+                child: TraceUInt {
+                    location: TraceScalarId(8),
+                    name: "any_seq",
+                    ty: UInt<16>,
+                    flow: Source,
+                },
+                formal_input: any_seq(
+                    UInt<16>,
+                ),
+            },
+            TraceModuleIO {
+                name: "count",
+                child: TraceUInt {
+                    location: TraceScalarId(0),
+                    name: "count",
+                    ty: UInt<8>,
+                    flow: Sink,
+                },
+                ty: UInt<8>,
+                flow: Sink,
+            },
+            TraceModuleIO {
+                name: "enable_assert",
+                child: TraceBool {
+                    location: TraceScalarId(1),
+                    name: "enable_assert",
+                    flow: Source,
+                },
+                ty: Bool,
+                flow: Source,
+            },
+            TraceModuleIO {
+                name: "any_seq_out",
+                child: TraceUInt {
+                    location: TraceScalarId(2),
+                    name: "any_seq_out",
+                    ty: UInt<16>,
+                    flow: Sink,
+                },
+                ty: UInt<16>,
+                flow: Sink,
+            },
+            TraceWire {
+                name: "cd",
+                child: TraceBundle {
+                    name: "cd",
+                    fields: [
+                        TraceClock {
+                            location: TraceScalarId(3),
+                            name: "clk",
+                            flow: Duplex,
+                        },
+                        TraceSyncReset {
+                            location: TraceScalarId(4),
+                            name: "rst",
+                            flow: Duplex,
+                        },
+                    ],
+                    ty: Bundle {
+                        /* offset = 0 */
+                        clk: Clock,
+                        /* offset = 1 */
+                        rst: SyncReset,
+                    },
+                    flow: Duplex,
+                },
+                ty: Bundle {
+                    /* offset = 0 */
+                    clk: Clock,
+                    /* offset = 1 */
+                    rst: SyncReset,
+                },
+            },
+            TraceReg {
+                name: "count_reg",
+                child: TraceUInt {
+                    location: TraceScalarId(7),
+                    name: "count_reg",
+                    ty: UInt<8>,
+                    flow: Duplex,
+                },
+                ty: UInt<8>,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(0),
+                ty: UInt<8>,
+            },
+            maybe_changed: true,
+            state: 0x02,
+            last_state: 0x01,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigBool {
+                index: StatePartIndex<BigSlots>(1),
+            },
+            maybe_changed: false,
+            state: 0x1,
+            last_state: 0x1,
+        },
+        SimTrace {
+            id: TraceScalarId(2),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<16>,
+            },
+            maybe_changed: true,
+            state: 0x04d2,
+            last_state: 0x04d2,
+        },
+        SimTrace {
+            id: TraceScalarId(3),
+            kind: BigClock {
+                index: StatePartIndex<BigSlots>(3),
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(4),
+            kind: BigSyncReset {
+                index: StatePartIndex<BigSlots>(4),
+            },
+            maybe_changed: true,
+            state: 0x0,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(5),
+            kind: BigClock {
+                index: StatePartIndex<BigSlots>(7),
+            },
+            maybe_changed: true,
+            state: 0x1,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(6),
+            kind: BigSyncReset {
+                index: StatePartIndex<BigSlots>(8),
+            },
+            maybe_changed: true,
+            state: 0x0,
+            last_state: 0x0,
+        },
+        SimTrace {
+            id: TraceScalarId(7),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(9),
+                ty: UInt<8>,
+            },
+            maybe_changed: true,
+            state: 0x02,
+            last_state: 0x01,
+        },
+        SimTrace {
+            id: TraceScalarId(8),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(25),
+                ty: UInt<16>,
+            },
+            maybe_changed: true,
+            state: 0x04d2,
+            last_state: 0x04d2,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    clocks_triggered: [
+        StatePartIndex<SmallSlots>(1),
+    ],
+    event_queue: EventQueue(EventQueueData {
+        instant: 66 μs,
+        events: {},
+    }),
+    waiting_sensitivity_sets_by_address: {},
+    waiting_sensitivity_sets_by_compiled_value: {},
+    asserts: [
+        CompiledAssert {
+            instantiated_module: InstantiatedModule(formal_counter: formal_counter),
+            stmt_formal: assert {
+                clk: Wire(formal_counter::cd: Bundle {
+                    /* offset = 0 */
+                    clk: Clock,
+                    /* offset = 1 */
+                    rst: SyncReset,
+                }).clk,
+                pred: CmpLeU {
+                    lhs: Reg {
+                        name: formal_counter::count_reg,
+                        ty: UInt<8>,
+                        clock_domain: Wire(formal_counter::cd: Bundle {
+                            /* offset = 0 */
+                            clk: Clock,
+                            /* offset = 1 */
+                            rst: SyncReset,
+                        }),
+                        init: Some(
+                            0x0_u8,
+                        ),
+                        ..
+                    },
+                    rhs: 0xA_u8,
+                    literal_bits: Err(
+                        NotALiteralExpr,
+                    ),
+                },
+                en: BitAndB {
+                    lhs: true,
+                    rhs: NotB {
+                        arg: CastSyncResetToBool {
+                            arg: formal_reset,
+                            literal_bits: Err(
+                                NotALiteralExpr,
+                            ),
+                        },
+                        literal_bits: Err(
+                            NotALiteralExpr,
+                        ),
+                    },
+                    literal_bits: Err(
+                        NotALiteralExpr,
+                    ),
+                },
+                text: "",
+                ..
+            },
+        },
+    ],
+    ..
+}

crates/fayalite/tests/sim/expected/test_formal_counter.vcd

@@ -0,0 +1,290 @@
+$timescale 1 ps $end
+$scope module formal_counter $end
+$var wire 1 ekAK2 formal_global_clock $end
+$var wire 1 qTY9h formal_reset $end
+$var wire 16 /roOY any_seq $end
+$var wire 8 }eN0d count $end
+$var wire 1 2f=;S enable_assert $end
+$var wire 16 L-uG? any_seq_out $end
+$scope struct cd $end
+$var wire 1 -e"5` clk $end
+$var wire 1 IC0;$ rst $end
+$upscope $end
+$var reg 8 ^:T_4 count_reg $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b0 }eN0d
+12f=;S
+b0 L-uG?
+0-e"5`
+1IC0;$
+0ekAK2
+1qTY9h
+b0 ^:T_4
+b0 /roOY
+$end
+#1000000
+b10011010010 L-uG?
+1-e"5`
+1ekAK2
+b10011010010 /roOY
+0IC0;$
+0qTY9h
+#2000000
+0-e"5`
+0ekAK2
+#3000000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#4000000
+0-e"5`
+0ekAK2
+#5000000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#6000000
+0-e"5`
+0ekAK2
+#7000000
+b11 }eN0d
+1-e"5`
+1ekAK2
+b11 ^:T_4
+#8000000
+0-e"5`
+0ekAK2
+#9000000
+b100 }eN0d
+1-e"5`
+1ekAK2
+b100 ^:T_4
+#10000000
+0-e"5`
+0ekAK2
+#11000000
+b101 }eN0d
+1-e"5`
+1ekAK2
+b101 ^:T_4
+#12000000
+0-e"5`
+0ekAK2
+#13000000
+b110 }eN0d
+1-e"5`
+1ekAK2
+b110 ^:T_4
+#14000000
+0-e"5`
+0ekAK2
+#15000000
+b111 }eN0d
+1-e"5`
+1ekAK2
+b111 ^:T_4
+#16000000
+0-e"5`
+0ekAK2
+#17000000
+b1000 }eN0d
+1-e"5`
+1ekAK2
+b1000 ^:T_4
+#18000000
+0-e"5`
+0ekAK2
+#19000000
+b1001 }eN0d
+1-e"5`
+1ekAK2
+b1001 ^:T_4
+#20000000
+0-e"5`
+0ekAK2
+#21000000
+b0 }eN0d
+1-e"5`
+1ekAK2
+b0 ^:T_4
+#22000000
+0-e"5`
+0ekAK2
+#23000000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#24000000
+0-e"5`
+0ekAK2
+#25000000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#26000000
+0-e"5`
+0ekAK2
+#27000000
+b11 }eN0d
+1-e"5`
+1ekAK2
+b11 ^:T_4
+#28000000
+0-e"5`
+0ekAK2
+#29000000
+b100 }eN0d
+1-e"5`
+1ekAK2
+b100 ^:T_4
+#30000000
+0-e"5`
+0ekAK2
+#31000000
+b101 }eN0d
+1-e"5`
+1ekAK2
+b101 ^:T_4
+#32000000
+0-e"5`
+0ekAK2
+#33000000
+b110 }eN0d
+1-e"5`
+1ekAK2
+b110 ^:T_4
+#34000000
+0-e"5`
+0ekAK2
+#35000000
+b111 }eN0d
+1-e"5`
+1ekAK2
+b111 ^:T_4
+#36000000
+0-e"5`
+0ekAK2
+#37000000
+b1000 }eN0d
+1-e"5`
+1ekAK2
+b1000 ^:T_4
+#38000000
+0-e"5`
+0ekAK2
+#39000000
+b1001 }eN0d
+1-e"5`
+1ekAK2
+b1001 ^:T_4
+#40000000
+0-e"5`
+0ekAK2
+#41000000
+b0 }eN0d
+1-e"5`
+1ekAK2
+b0 ^:T_4
+#42000000
+0-e"5`
+0ekAK2
+#43000000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#44000000
+0-e"5`
+0ekAK2
+#45000000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#46000000
+0-e"5`
+0ekAK2
+#47000000
+b11 }eN0d
+1-e"5`
+1ekAK2
+b11 ^:T_4
+#48000000
+0-e"5`
+0ekAK2
+#49000000
+b100 }eN0d
+1-e"5`
+1ekAK2
+b100 ^:T_4
+#50000000
+0-e"5`
+0ekAK2
+#51000000
+b101 }eN0d
+1-e"5`
+1ekAK2
+b101 ^:T_4
+#52000000
+0-e"5`
+0ekAK2
+#53000000
+b110 }eN0d
+1-e"5`
+1ekAK2
+b110 ^:T_4
+#54000000
+0-e"5`
+0ekAK2
+#55000000
+b111 }eN0d
+1-e"5`
+1ekAK2
+b111 ^:T_4
+#56000000
+0-e"5`
+0ekAK2
+#57000000
+b1000 }eN0d
+1-e"5`
+1ekAK2
+b1000 ^:T_4
+#58000000
+0-e"5`
+0ekAK2
+#59000000
+b1001 }eN0d
+1-e"5`
+1ekAK2
+b1001 ^:T_4
+#60000000
+0-e"5`
+0ekAK2
+#61000000
+b0 }eN0d
+1-e"5`
+1ekAK2
+b0 ^:T_4
+#62000000
+0-e"5`
+0ekAK2
+#63000000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#64000000
+0-e"5`
+0ekAK2
+#65000000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#66000000

crates/fayalite/tests/sim/expected/test_formal_counter_assert.vcd

@@ -0,0 +1,194 @@
+$timescale 1 ps $end
+$scope module formal_counter $end
+$var wire 1 ekAK2 formal_global_clock $end
+$var wire 1 qTY9h formal_reset $end
+$var wire 16 /roOY any_seq $end
+$var wire 8 }eN0d count $end
+$var wire 1 2f=;S enable_assert $end
+$var wire 16 L-uG? any_seq_out $end
+$scope struct cd $end
+$var wire 1 -e"5` clk $end
+$var wire 1 IC0;$ rst $end
+$upscope $end
+$var reg 8 ^:T_4 count_reg $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b0 }eN0d
+02f=;S
+b0 L-uG?
+0-e"5`
+1IC0;$
+0ekAK2
+1qTY9h
+b0 ^:T_4
+b0 /roOY
+$end
+#500000
+b10011010010 L-uG?
+1-e"5`
+1ekAK2
+b10011010010 /roOY
+0IC0;$
+0qTY9h
+#1000000
+0-e"5`
+0ekAK2
+#1500000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#2000000
+0-e"5`
+0ekAK2
+#2500000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#3000000
+0-e"5`
+0ekAK2
+#3500000
+b11 }eN0d
+1-e"5`
+1ekAK2
+b11 ^:T_4
+#4000000
+0-e"5`
+0ekAK2
+#4500000
+b100 }eN0d
+1-e"5`
+1ekAK2
+b100 ^:T_4
+#5000000
+0-e"5`
+0ekAK2
+#5500000
+b101 }eN0d
+1-e"5`
+1ekAK2
+b101 ^:T_4
+#6000000
+0-e"5`
+0ekAK2
+#6500000
+b110 }eN0d
+1-e"5`
+1ekAK2
+b110 ^:T_4
+#7000000
+0-e"5`
+0ekAK2
+#7500000
+b111 }eN0d
+1-e"5`
+1ekAK2
+b111 ^:T_4
+#8000000
+0-e"5`
+0ekAK2
+#8500000
+b1000 }eN0d
+1-e"5`
+1ekAK2
+b1000 ^:T_4
+#9000000
+0-e"5`
+0ekAK2
+#9500000
+b1001 }eN0d
+1-e"5`
+1ekAK2
+b1001 ^:T_4
+#10000000
+0-e"5`
+0ekAK2
+#10500000
+b0 }eN0d
+1-e"5`
+1ekAK2
+b0 ^:T_4
+#11000000
+0-e"5`
+0ekAK2
+#11500000
+b1 }eN0d
+1-e"5`
+1ekAK2
+b1 ^:T_4
+#12000000
+0-e"5`
+0ekAK2
+#12500000
+b10 }eN0d
+1-e"5`
+1ekAK2
+b10 ^:T_4
+#13000000
+0-e"5`
+0ekAK2
+#13500000
+b11 }eN0d
+1-e"5`
+1ekAK2
+b11 ^:T_4
+#14000000
+0-e"5`
+0ekAK2
+#14500000
+b100 }eN0d
+1-e"5`
+1ekAK2
+b100 ^:T_4
+#15000000
+0-e"5`
+0ekAK2
+#15500000
+b101 }eN0d
+1-e"5`
+1ekAK2
+b101 ^:T_4
+#16000000
+0-e"5`
+0ekAK2
+#16500000
+b110 }eN0d
+1-e"5`
+1ekAK2
+b110 ^:T_4
+#17000000
+12f=;S
+0-e"5`
+0ekAK2
+#17500000
+b111 }eN0d
+1-e"5`
+1ekAK2
+b111 ^:T_4
+#18000000
+0-e"5`
+0ekAK2
+#18500000
+b1000 }eN0d
+1-e"5`
+1ekAK2
+b1000 ^:T_4
+#19000000
+0-e"5`
+0ekAK2
+#19500000
+b1001 }eN0d
+1-e"5`
+1ekAK2
+b1001 ^:T_4
+#20000000
+0-e"5`
+0ekAK2
+#20500000
+b0 }eN0d
+1-e"5`
+1ekAK2
+b0 ^:T_4

crates/fayalite/tests/ui/simvalue_is_not_internable.stderr

@@ -75,7 +75,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs
@@ -214,7 +214,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs
@@ -326,7 +326,7 @@ note: required because it appears within the type `Vec<DynSimOnlyValue>`
 note: required because it appears within the type `OpaqueSimValue`
     --> src/ty.rs
      |
- 896 | pub struct OpaqueSimValue {
+ 929 | pub struct OpaqueSimValue {
      |            ^^^^^^^^^^^^^^
 note: required because it appears within the type `value::SimValueInner<()>`
     --> src/sim/value.rs

crates/fayalite/visit_types.json

@@ -151,6 +151,11 @@
                 "$kind": "Opaque"
             }
         },
+        "NameIdOrGlobal": {
+            "data": {
+                "$kind": "ManualImpl"
+            }
+        },
         "ScopedNameId": {
             "data": {
                 "$kind": "Struct",
@@ -1043,6 +1048,22 @@
             "fold_where": "T: Fold<State>",
             "visit_where": "T: Visit<State>"
         },
+        "ops::SimIoForGlobal": {
+            "data": {
+                "$kind": "Struct",
+                "$constructor": "ops::SimIoForGlobal::new",
+                "global()": "Visible"
+            }
+        },
+        "ops::StructuralEq": {
+            "data": {
+                "$kind": "Struct",
+                "$constructor": "ops::StructuralEq::with_flags",
+                "lhs()": "Visible",
+                "rhs()": "Visible",
+                "flags()": "Opaque"
+            }
+        },
         "BlockId": {
             "data": {
                 "$kind": "Opaque"
@@ -1277,7 +1298,9 @@
                 "RegSync": "Visible",
                 "RegAsync": "Visible",
                 "Wire": "Visible",
-                "Instance": "Visible"
+                "Instance": "Visible",
+                "FormalInput": "Visible",
+                "SimIoForGlobal": "Visible"
             }
         },
         "TargetChild": {
@@ -1349,6 +1372,21 @@
             "generics": "<T: Type>",
             "fold_where": "T: Fold<State>",
             "visit_where": "T: Visit<State>"
+        },
+        "FormalInput": {
+            "data": {
+                "$kind": "Struct",
+                "$constructor": "FormalInput::new",
+                "kind()": "Visible",
+                "name_id()": "Visible",
+                "ty()": "Visible",
+                "source_location()": "Visible"
+            }
+        },
+        "FormalInputKind": {
+            "data": {
+                "$kind": "Opaque"
+            }
         }
     }
 }

scripts/check-copyright.sh

@@ -47,7 +47,7 @@ function main()
         */LICENSE.md|*/Notices.txt)
             # copyright file
             ;;
-        /crates/fayalite/tests/ui/*.stderr|/crates/fayalite/tests/sim/expected/*.vcd|/crates/fayalite/tests/sim/expected/*.txt)
+        /crates/fayalite/tests/ui/*.stderr|/crates/fayalite/tests/expected/*.vcd|/crates/fayalite/tests/sim/expected/*.vcd|/crates/fayalite/tests/sim/expected/*.txt)
             # file that can't contain copyright header
             ;;
         /.forgejo/workflows/*.yml|*/.gitignore|*.toml|*/Makefile|*/_CoqProject)