diff --git a/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs b/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
index f7ad68d..451bc7e 100644
--- a/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
+++ b/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
                     }
 
diff --git a/crates/fayalite-proc-macros-impl/src/hdl_enum.rs b/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
index e9f013b..68fcc02 100644
--- a/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
+++ b/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 {
-                        <#target #type_generics as ::fayalite::ty::SimValueDisplay>::sim_value_display(self, f)
+                    fn fmt(
+                        &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,
diff --git a/crates/fayalite/src/array.rs b/crates/fayalite/src/array.rs
index fa754fd..95ecb8b 100644
--- a/crates/fayalite/src/array.rs
+++ b/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))
diff --git a/crates/fayalite/src/build/graph.rs b/crates/fayalite/src/build/graph.rs
index bed8829..e46f0a4 100644
--- a/crates/fayalite/src/build/graph.rs
+++ b/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 {
diff --git a/crates/fayalite/src/bundle.rs b/crates/fayalite/src/bundle.rs
index 5fad35c..5a97944 100644
--- a/crates/fayalite/src/bundle.rs
+++ b/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(
diff --git a/crates/fayalite/src/expr.rs b/crates/fayalite/src/expr.rs
index eb4bf0f..f9f239f 100644
--- a/crates/fayalite/src/expr.rs
+++ b/crates/fayalite/src/expr.rs
@@ -221,6 +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>),
@@ -701,6 +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>)?
@@ -729,6 +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(
                 $cmp_value_lhs: Self,
@@ -912,6 +916,7 @@ impl_hdl_cmp! {
     #[
         impl_helper = HdlPartialEqImplHelper,
         impl_helper_sealed = HdlPartialEqImplHelperSealed,
+        try_structural_eq = TRY_STRUCTURAL_EQ,
     ]
     pub trait HdlPartialEq<Rhs: ValueType>:
         ValueType<Type: HdlPartialEqImpl<Rhs::Type> >
diff --git a/crates/fayalite/src/expr/ops.rs b/crates/fayalite/src/expr/ops.rs
index 5d335a5..7c5af38 100644
--- a/crates/fayalite/src/expr/ops.rs
+++ b/crates/fayalite/src/expr/ops.rs
@@ -22,7 +22,7 @@ use crate::{
         Bool, BoolOrIntType, DynSize, IntType, KnownSize, SInt, SIntType, SIntValue, Size, UInt,
         UIntType, UIntValue,
     },
-    intern::{Intern, Interned},
+    intern::{Intern, Interned, MemoizeGeneric},
     phantom_const::{PhantomConst, PhantomConstValue},
     reset::{
         AsyncReset, Reset, ResetType, ResetTypeDispatch, SyncReset, ToAsyncReset, ToReset,
@@ -2984,6 +2984,7 @@ macro_rules! impl_compare_op {
         #[to_dyn_type($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;
@@ -3045,6 +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,
                 $lhs_compare_value: Cow<'_, <Self as Type>::SimValue>,
@@ -3065,6 +3067,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => lhs, rhs => rhs)]
     #[to_cmp_value(lhs_value => &*lhs_value, rhs_value => &*rhs_value)]
     #[type(Bool, Bool)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqB; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeB; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3088,6 +3091,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(UIntType<LhsWidth>, UIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqU; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeU; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3112,6 +3116,7 @@ impl_compare_op! {
     #[to_dyn_type(lhs => Expr::as_dyn_int(lhs), rhs => Expr::as_dyn_int(rhs))]
     #[to_cmp_value(lhs_value => &lhs_value.to_bigint(), rhs_value => &rhs_value.to_bigint())]
     #[type(SIntType<LhsWidth>, SIntType<RhsWidth>)]
+    #[try_structural_eq = TRY_STRUCTURAL_EQ]
     #[trait(HdlPartialEqImpl)]
     struct CmpEqS; fn cmp_value_eq(); fn cmp_expr_eq(); PartialEq::eq();
     struct CmpNeS; fn cmp_value_ne(); fn cmp_expr_ne(); PartialEq::ne();
@@ -3133,6 +3138,8 @@ impl_compare_op! {
 macro_rules! impl_compare_forwards_to_bool {
     ($ty:ident) => {
         impl HdlPartialEqImpl<Self> for $ty {
+            const TRY_STRUCTURAL_EQ: bool = true;
+
             #[track_caller]
             fn cmp_value_eq(
                 _lhs: Self,
@@ -4948,3 +4955,270 @@ impl ToExpr for SimIoForGlobal {
         }
     }
 }
+
+#[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,
+        }
+    }
+}
diff --git a/crates/fayalite/src/expr/target.rs b/crates/fayalite/src/expr/target.rs
index d7775ec..84d3ace 100644
--- a/crates/fayalite/src/expr/target.rs
+++ b/crates/fayalite/src/expr/target.rs
@@ -63,7 +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()")
     }
 }
 
diff --git a/crates/fayalite/src/firrtl.rs b/crates/fayalite/src/firrtl.rs
index 60cc0d1..cad55a8 100644
--- a/crates/fayalite/src/firrtl.rs
+++ b/crates/fayalite/src/firrtl.rs
@@ -7,7 +7,7 @@ use crate::{
     bundle::{BundleField, BundleType},
     enum_::{EnumType, EnumVariant},
     expr::{
-        ExprEnum,
+        CastToImpl, ExprEnum,
         ops::{self, VariantAccess},
         target::{
             Target, TargetBase, TargetPathArrayElement, TargetPathBundleField, TargetPathElement,
@@ -389,6 +389,7 @@ struct BlockDefinitionsCache {
     cast_bits_to_array_exprs: RefCell<HashMap<(String, Array), String>>,
     cast_bits_to_phantom_const_exprs: RefCell<HashMap<(String, PhantomConst), String>>,
     per_module_formal_inputs: RefCell<HashMap<(FormalInput, bool), String>>,
+    structural_eq_exprs: RefCell<HashMap<(String, String), String>>,
 }
 
 struct BlockDefinitions<'a> {
@@ -1774,6 +1775,143 @@ endmodule
             },
         )
     }
+    fn expr_structural_eq_bit<T: CastToImpl<Bool>>(
+        &mut self,
+        lhs: Expr<CanonicalType>,
+        rhs: Expr<CanonicalType>,
+        definitions: &BlockDefinitions<'_>,
+        const_ty: bool,
+    ) -> Result<String> {
+        self.expr_binary(
+            "eq",
+            Expr::<T>::from_canonical(lhs).cast_to(Bool),
+            Expr::<T>::from_canonical(rhs).cast_to(Bool),
+            definitions,
+            const_ty,
+        )
+    }
+    fn expr_structural_eq(
+        &mut self,
+        ty: CanonicalType,
+        lhs: String,
+        rhs: String,
+        definitions: &BlockDefinitions<'_>,
+        const_ty: bool,
+    ) -> Result<String> {
+        match ty {
+            CanonicalType::UInt(_) | CanonicalType::SInt(_) | CanonicalType::Bool(_) => {
+                Ok(format!("eq({lhs}, {rhs})"))
+            }
+            CanonicalType::Array(ty) => {
+                if ty.len() == 1 {
+                    return self.expr_structural_eq(
+                        ty.element(),
+                        lhs + "[0]",
+                        rhs + "[0]",
+                        definitions,
+                        const_ty,
+                    );
+                } else if ty.is_empty() {
+                    return Ok(self.bool_literal(true));
+                }
+                definitions.get_or_write_definition(
+                    (lhs, rhs),
+                    |c| &c.structural_eq_exprs,
+                    |definitions, (lhs, rhs)| {
+                        let mut retval = None;
+                        for array_index in 0..ty.len() {
+                            let element_eq = self.expr_structural_eq(
+                                ty.element(),
+                                format!("{lhs}[{array_index}]"),
+                                format!("{rhs}[{array_index}]"),
+                                &definitions,
+                                const_ty,
+                            )?;
+                            retval = match retval {
+                                Some(old_eq) => {
+                                    let ident = self.module.ns.make_new("_array_structural_eq");
+                                    definitions
+                                        .add_definition_line(format_args!("wire {ident}: UInt<1>"));
+                                    definitions.add_definition_line(format_args!(
+                                        "connect {ident}, and({old_eq}, {element_eq})"
+                                    ));
+                                    Some(ident.to_string())
+                                }
+                                None => Some(element_eq),
+                            };
+                        }
+                        Ok(retval.expect("known to be Some"))
+                    },
+                )
+            }
+            CanonicalType::Enum(ty) => {
+                let lhs = self.expr_cast_enum_to_bits(
+                    lhs,
+                    ty,
+                    definitions,
+                    Indent {
+                        indent_depth: &Cell::new(0),
+                        indent: self.indent.indent,
+                    },
+                )?;
+                let rhs = self.expr_cast_enum_to_bits(
+                    rhs,
+                    ty,
+                    definitions,
+                    Indent {
+                        indent_depth: &Cell::new(0),
+                        indent: self.indent.indent,
+                    },
+                )?;
+                Ok(format!("eq({lhs}, {rhs})"))
+            }
+            CanonicalType::Bundle(ty) => {
+                let fields = ty.fields();
+                if fields.is_empty() {
+                    return Ok(self.bool_literal(true));
+                }
+                definitions.get_or_write_definition(
+                    (lhs, rhs),
+                    |c| &c.structural_eq_exprs,
+                    |definitions, (lhs, rhs)| {
+                        let mut retval = None;
+                        for field in fields {
+                            let field_ident = self.type_state.get_bundle_field(ty, field.name)?;
+                            let field_eq = self.expr_structural_eq(
+                                field.ty,
+                                format!("{lhs}.{field_ident}"),
+                                format!("{rhs}.{field_ident}"),
+                                &definitions,
+                                const_ty,
+                            )?;
+                            retval = match retval {
+                                Some(old_eq) => {
+                                    let ident = self.module.ns.make_new("_bundle_structural_eq");
+                                    definitions
+                                        .add_definition_line(format_args!("wire {ident}: UInt<1>"));
+                                    definitions.add_definition_line(format_args!(
+                                        "connect {ident}, and({old_eq}, {field_eq})"
+                                    ));
+                                    Some(ident.to_string())
+                                }
+                                None => Some(field_eq),
+                            };
+                        }
+                        Ok(retval.expect("known to be Some"))
+                    },
+                )
+            }
+            CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_) => Ok(format!("eq(asUInt({lhs}), asUInt({rhs}))")),
+            CanonicalType::PhantomConst(_) => Ok(self.bool_literal(true)),
+            CanonicalType::DynSimOnly(_) => Err(FirrtlError::SimOnlyValuesAreNotPermitted.into()),
+            CanonicalType::TraceAsString(ty) => {
+                self.expr_structural_eq(ty.inner_ty(), lhs, rhs, definitions, const_ty)
+            }
+        }
+    }
     fn expr(
         &mut self,
         expr: Expr<CanonicalType>,
@@ -2117,6 +2255,13 @@ endmodule
             ExprEnum::TraceAsStringAsInner(expr) => {
                 self.expr(Expr::canonical(expr.arg()), definitions, const_ty)
             }
+            ExprEnum::StructuralEq(expr) => {
+                let ty = expr.lhs().ty();
+                assert_eq!(ty, expr.rhs().ty());
+                let lhs = self.expr(expr.lhs(), definitions, const_ty)?;
+                let rhs = self.expr(expr.rhs(), definitions, const_ty)?;
+                self.expr_structural_eq(ty, lhs, rhs, definitions, const_ty)
+            }
             ExprEnum::ModuleIO(expr) => Ok(self.module.ns.get(expr.name_id()).to_string()),
             ExprEnum::Instance(expr) => {
                 assert!(!const_ty, "not a constant");
diff --git a/crates/fayalite/src/int/uint_in_range.rs b/crates/fayalite/src/int/uint_in_range.rs
index edf2e25..4292d08 100644
--- a/crates/fayalite/src/int/uint_in_range.rs
+++ b/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>,
diff --git a/crates/fayalite/src/module.rs b/crates/fayalite/src/module.rs
index 2535694..e899fd7 100644
--- a/crates/fayalite/src/module.rs
+++ b/crates/fayalite/src/module.rs
@@ -2206,6 +2206,7 @@ impl transform::visit::Visitor for AssertExprValidity<'_> {
             | ExprEnum::CastBitsTo(_)
             | ExprEnum::ToTraceAsString(_)
             | ExprEnum::TraceAsStringAsInner(_)
+            | ExprEnum::StructuralEq(_)
             | ExprEnum::FormalInput(_) => v.default_visit(self),
             ExprEnum::VariantAccess(_)
             | ExprEnum::ModuleIO(_)
@@ -2247,7 +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()
@@ -2268,7 +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!(
diff --git a/crates/fayalite/src/module/transform.rs b/crates/fayalite/src/module/transform.rs
index 063a1a3..7eec4cf 100644
--- a/crates/fayalite/src/module/transform.rs
+++ b/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;
diff --git a/crates/fayalite/src/module/transform/deduce_resets.rs b/crates/fayalite/src/module/transform/deduce_resets.rs
index 611401b..50a58c5 100644
--- a/crates/fayalite/src/module/transform/deduce_resets.rs
+++ b/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)),
@@ -1653,6 +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];
 
diff --git a/crates/fayalite/src/module/transform/deduce_structural_eq_flags.rs b/crates/fayalite/src/module/transform/deduce_structural_eq_flags.rs
new file mode 100644
index 0000000..009293c
--- /dev/null
+++ b/crates/fayalite/src/module/transform/deduce_structural_eq_flags.rs
@@ -0,0 +1,1606 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+use crate::{
+    bundle::{BundleField, BundleType},
+    enum_::{EnumType, EnumVariant},
+    expr::{
+        ExprEnum, ToLiteralBits,
+        ops::{
+            ArrayIndex, FieldAccess, StructuralEq, StructuralEqFlags, TraceAsStringAsInner,
+            VariantAccess,
+        },
+        target::TargetBase,
+    },
+    intern::{Intern, InternSlice, Interned, MemoizeGeneric},
+    module::{
+        ModuleBody, Stmt, StmtConnect, StmtDeclaration, StmtInstance, StmtReg, StmtWire,
+        transform::visit::{Fold, Folder, Visit, Visitor},
+    },
+    prelude::*,
+    util::{
+        BitSliceWriteWithBase, HashMap,
+        indented_print::{PushIndent, indented_println},
+        union_find_map::{Entry, UnionFindMap},
+    },
+};
+use bitvec::{order::Lsb0, view::BitView};
+use std::{convert::Infallible, fmt};
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+enum FlagsTree {
+    Enum {
+        variants: Interned<[Option<Interned<FlagsTree>>]>,
+        /// invariant -- if this is true all children must also have [`FlagsTree::assume_padding_is_zeroed()`] return true
+        assume_padding_is_zeroed: bool,
+    },
+    Bundle {
+        fields: Interned<[Interned<FlagsTree>]>,
+        /// invariant -- if this is true all children must also have [`FlagsTree::assume_padding_is_zeroed()`] return true
+        assume_padding_is_zeroed: bool,
+    },
+    NoPadding,
+}
+
+impl fmt::Debug for FlagsTree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Enum {
+                variants,
+                assume_padding_is_zeroed,
+            } => f
+                .debug_struct("Enum")
+                .field(
+                    "variants",
+                    &fmt::from_fn(|f| {
+                        f.debug_list()
+                            .entries(variants.iter().map(|variant| {
+                                fmt::from_fn(move |f| match variant {
+                                    Some(variant) => variant.fmt(f),
+                                    None => f.write_str("None"),
+                                })
+                            }))
+                            .finish()
+                    }),
+                )
+                .field("assume_padding_is_zeroed", assume_padding_is_zeroed)
+                .finish(),
+            Self::Bundle {
+                fields,
+                assume_padding_is_zeroed,
+            } => f
+                .debug_struct("Bundle")
+                .field("fields", fields)
+                .field("assume_padding_is_zeroed", assume_padding_is_zeroed)
+                .finish(),
+            Self::NoPadding => f.write_str("NoPadding"),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+enum FlagsTreeSourceValue<'a> {
+    LiteralBits { bits: &'a BitSlice },
+    Flags { assume_padding_is_zeroed: bool },
+}
+
+impl<'a> fmt::Debug for FlagsTreeSourceValue<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::LiteralBits { bits } => f
+                .debug_struct("LiteralBits")
+                .field(
+                    "bits",
+                    &fmt::from_fn(|f| write!(f, "{:#b}", BitSliceWriteWithBase(bits))),
+                )
+                .finish(),
+            Self::Flags {
+                assume_padding_is_zeroed,
+            } => f
+                .debug_struct("Flags")
+                .field("assume_padding_is_zeroed", assume_padding_is_zeroed)
+                .finish(),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+enum FlagsTreeSourceValueOwned {
+    LiteralBits { bits: Interned<BitSlice> },
+    Flags { assume_padding_is_zeroed: bool },
+}
+
+impl FlagsTreeSourceValueOwned {
+    fn as_ref(&self) -> FlagsTreeSourceValue<'_> {
+        match *self {
+            Self::LiteralBits { ref bits } => FlagsTreeSourceValue::LiteralBits { bits },
+            Self::Flags {
+                assume_padding_is_zeroed,
+            } => FlagsTreeSourceValue::Flags {
+                assume_padding_is_zeroed,
+            },
+        }
+    }
+}
+
+impl<'a> FlagsTreeSourceValue<'a> {
+    fn to_owned(self) -> FlagsTreeSourceValueOwned {
+        match self {
+            Self::LiteralBits { bits } => FlagsTreeSourceValueOwned::LiteralBits {
+                bits: bits.intern(),
+            },
+            Self::Flags {
+                assume_padding_is_zeroed,
+            } => FlagsTreeSourceValueOwned::Flags {
+                assume_padding_is_zeroed,
+            },
+        }
+    }
+    fn visit_array_body<T, R: FromIterator<T>>(
+        self,
+        element_ty: CanonicalType,
+        f: impl FnMut(Self) -> T,
+    ) -> R {
+        match self {
+            Self::LiteralBits { bits } => {
+                let bit_width = element_ty.bit_width();
+                if bit_width == 0 {
+                    R::from_iter([])
+                } else {
+                    bits.chunks(bit_width)
+                        .map(|bits| Self::LiteralBits { bits })
+                        .map(f)
+                        .collect()
+                }
+            }
+            Self::Flags { .. } => [self].into_iter().map(f).collect(),
+        }
+    }
+    fn visit_bundle_body<T, R: FromIterator<T>>(
+        self,
+        bundle: Bundle,
+        mut f: impl FnMut(usize, &BundleField, Self) -> T,
+    ) -> R {
+        match self {
+            Self::LiteralBits { bits } => bundle
+                .fields()
+                .iter()
+                .enumerate()
+                .scan(bits, |bundle_bits, (field_index, field)| {
+                    let field_bit_width = field.ty.bit_width();
+                    let bits;
+                    (bits, *bundle_bits) = bundle_bits.split_at(field_bit_width);
+                    Some(f(field_index, field, Self::LiteralBits { bits }))
+                })
+                .collect(),
+            Self::Flags { .. } => bundle
+                .fields()
+                .iter()
+                .enumerate()
+                .map(move |(field_index, field)| f(field_index, field, self))
+                .collect(),
+        }
+    }
+    fn visit_enum_body<T, R: FromIterator<T>>(
+        self,
+        enum_: Enum,
+        debug_trace: bool,
+        mut f: impl FnMut(&EnumVariant, Self) -> T,
+    ) -> (R, bool) {
+        let collected;
+        let padding_is_zeroed;
+        match self {
+            Self::LiteralBits { bits } => {
+                let mut discriminant = 0usize;
+                let discriminant_bit_width = enum_.discriminant_bit_width();
+                let (discriminant_bits, bits) = bits.split_at(discriminant_bit_width);
+                if debug_trace {
+                    indented_println!(
+                        "discriminant_bits={:#b}",
+                        BitSliceWriteWithBase(discriminant_bits)
+                    );
+                }
+                discriminant.view_bits_mut::<Lsb0>()[..discriminant_bit_width]
+                    .copy_from_bitslice(discriminant_bits);
+                let (bits, padding) = bits.split_at(
+                    enum_
+                        .variants()
+                        .get(discriminant)
+                        .and_then(|variant| variant.ty)
+                        .map_or(0, |variant_ty| variant_ty.bit_width()),
+                );
+                if debug_trace {
+                    indented_println!(
+                        "bits={:#b}\npadding={:#b}",
+                        BitSliceWriteWithBase(bits),
+                        BitSliceWriteWithBase(padding),
+                    );
+                }
+                collected = enum_
+                    .variants()
+                    .iter()
+                    .enumerate()
+                    .map(|(variant_index, variant)| {
+                        f(
+                            variant,
+                            if variant_index == discriminant {
+                                Self::LiteralBits { bits }
+                            } else {
+                                Self::Flags {
+                                    assume_padding_is_zeroed: true,
+                                }
+                            },
+                        )
+                    })
+                    .collect();
+                padding_is_zeroed = !padding.any();
+                if debug_trace {
+                    indented_println!("padding_is_zeroed={padding_is_zeroed:?}");
+                }
+            }
+            Self::Flags {
+                assume_padding_is_zeroed,
+            } => {
+                collected = enum_
+                    .variants()
+                    .iter()
+                    .map(|variant| f(variant, self))
+                    .collect();
+                padding_is_zeroed = assume_padding_is_zeroed;
+            }
+        }
+        (collected, padding_is_zeroed)
+    }
+}
+
+impl FlagsTree {
+    fn contains_padding(&self) -> bool {
+        match self {
+            Self::NoPadding => false,
+            Self::Enum { .. } | Self::Bundle { .. } => true,
+        }
+    }
+    fn assume_padding_is_zeroed(&self) -> bool {
+        match *self {
+            Self::Enum {
+                assume_padding_is_zeroed,
+                ..
+            }
+            | Self::Bundle {
+                assume_padding_is_zeroed,
+                ..
+            } => assume_padding_is_zeroed,
+            Self::NoPadding => true,
+        }
+    }
+    fn new_inner<'a>(
+        ty: &CanonicalType,
+        source_value: FlagsTreeSourceValue<'a>,
+        debug_trace: bool,
+    ) -> Interned<Self> {
+        let _push_indent;
+        if debug_trace {
+            indented_println!("FlagsTree::new_inner()");
+            _push_indent = PushIndent::new();
+            indented_println!("ty: {ty:?}");
+            indented_println!("source_value: {source_value:?}");
+        }
+        let retval = match ty {
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => Self::NoPadding.intern_sized(),
+            CanonicalType::Array(ty) => {
+                let mut retval = None;
+                let element_ty = ty.element();
+                let () =
+                    source_value.visit_array_body(element_ty, |source_value| match &mut retval {
+                        Some(retval) => {
+                            *retval = FlagsTree::new(element_ty, source_value, debug_trace)
+                                .merged(*retval)
+                        }
+                        None => retval = Some(Self::new(element_ty, source_value, debug_trace)),
+                    });
+                retval.unwrap_or_else(|| Self::NoPadding.intern_sized())
+            }
+            CanonicalType::Enum(ty) => {
+                let mut expected_bit_width = None;
+                let mut contains_padding = false;
+                let mut assume_padding_is_zeroed = true;
+                let (variants, padding_is_zeroed): (Vec<_>, _) =
+                    source_value.visit_enum_body(*ty, debug_trace, |variant, source_value| {
+                        let (variant_flags_tree, bit_width) = if let Some(variant_ty) = variant.ty {
+                            let variant_flags_tree =
+                                Self::new(variant_ty, source_value, debug_trace);
+                            contains_padding |= variant_flags_tree.contains_padding();
+                            assume_padding_is_zeroed &=
+                                variant_flags_tree.assume_padding_is_zeroed();
+                            (Some(variant_flags_tree), variant_ty.bit_width())
+                        } else {
+                            (None, 0)
+                        };
+                        if expected_bit_width
+                            .replace(bit_width)
+                            .is_some_and(|v| v != bit_width)
+                        {
+                            contains_padding = true;
+                        }
+                        variant_flags_tree
+                    });
+                assume_padding_is_zeroed &= padding_is_zeroed;
+                if contains_padding {
+                    Self::Enum {
+                        variants: variants.intern_slice(),
+                        assume_padding_is_zeroed,
+                    }
+                    .intern_sized()
+                } else {
+                    Self::NoPadding.intern_sized()
+                }
+            }
+            CanonicalType::Bundle(ty) => {
+                let mut contains_padding = false;
+                let mut assume_padding_is_zeroed = true;
+                let fields: Vec<_> =
+                    source_value.visit_bundle_body(*ty, |_field_index, field, source_value| {
+                        let flags_tree = Self::new(field.ty, source_value, debug_trace);
+                        contains_padding |= flags_tree.contains_padding();
+                        assume_padding_is_zeroed &= flags_tree.assume_padding_is_zeroed();
+                        flags_tree
+                    });
+                if contains_padding {
+                    Self::Bundle {
+                        fields: fields.intern_slice(),
+                        assume_padding_is_zeroed,
+                    }
+                    .intern_sized()
+                } else {
+                    Self::NoPadding.intern_sized()
+                }
+            }
+            CanonicalType::TraceAsString(ty) => Self::new(ty.inner_ty(), source_value, debug_trace),
+        };
+        if debug_trace {
+            indented_println!("return: {retval:#?}");
+        }
+        retval
+    }
+    fn new(
+        ty: CanonicalType,
+        source_value: FlagsTreeSourceValue<'_>,
+        debug_trace: bool,
+    ) -> Interned<Self> {
+        #[derive(Copy, Clone, PartialEq, Eq, Hash)]
+        struct MyMemoize {
+            debug_trace: bool,
+        }
+        enum InputCow<'a> {
+            Borrowed {
+                ty: &'a CanonicalType,
+                source_value: FlagsTreeSourceValue<'a>,
+            },
+            Owned {
+                ty: CanonicalType,
+                source_value: FlagsTreeSourceValueOwned,
+            },
+        }
+        impl MemoizeGeneric for MyMemoize {
+            type InputRef<'a> = (&'a CanonicalType, FlagsTreeSourceValue<'a>);
+            type InputOwned = (CanonicalType, FlagsTreeSourceValueOwned);
+            type InputCow<'a> = InputCow<'a>;
+            type Output = Interned<FlagsTree>;
+
+            fn input_eq(a: Self::InputRef<'_>, b: Self::InputRef<'_>) -> bool {
+                a == b
+            }
+
+            fn input_borrow(input: &Self::InputOwned) -> Self::InputRef<'_> {
+                let (ty, source_value) = input;
+                (ty, source_value.as_ref())
+            }
+
+            fn input_cow_into_owned(input: Self::InputCow<'_>) -> Self::InputOwned {
+                match input {
+                    InputCow::Borrowed { ty, source_value } => (*ty, source_value.to_owned()),
+                    InputCow::Owned { ty, source_value } => (ty, source_value),
+                }
+            }
+
+            fn input_cow_borrow<'a>(input: &'a Self::InputCow<'_>) -> Self::InputRef<'a> {
+                match input {
+                    &InputCow::Borrowed { ty, source_value } => (ty, source_value),
+                    InputCow::Owned { ty, source_value } => (ty, source_value.as_ref()),
+                }
+            }
+
+            fn input_cow_from_owned<'a>(input: Self::InputOwned) -> Self::InputCow<'a> {
+                let (ty, source_value) = input;
+                InputCow::Owned { ty, source_value }
+            }
+
+            fn input_cow_from_ref(input: Self::InputRef<'_>) -> Self::InputCow<'_> {
+                let (ty, source_value) = input;
+                InputCow::Borrowed { ty, source_value }
+            }
+
+            fn inner(self, input: Self::InputRef<'_>) -> Self::Output {
+                let (ty, source_value) = input;
+                FlagsTree::new_inner(ty, source_value, self.debug_trace)
+            }
+        }
+        MyMemoize { debug_trace }.get((&ty, source_value))
+    }
+    #[must_use]
+    fn merged(self, other: Interned<FlagsTree>) -> Interned<FlagsTree> {
+        if self == *other {
+            return other;
+        }
+        match (self, *other) {
+            (
+                Self::Enum {
+                    variants: l_variants,
+                    assume_padding_is_zeroed: l_assume_padding_is_zeroed,
+                },
+                Self::Enum {
+                    variants: r_variants,
+                    assume_padding_is_zeroed: r_assume_padding_is_zeroed,
+                },
+            ) => {
+                let variants = Interned::from_iter(l_variants.iter().zip(&r_variants).map(
+                    |(&l_variant, &r_variant)| {
+                        l_variant
+                            .zip(r_variant)
+                            .map(|(l_variant, r_variant)| l_variant.merged(r_variant))
+                    },
+                ));
+                let assume_padding_is_zeroed =
+                    l_assume_padding_is_zeroed & r_assume_padding_is_zeroed;
+                Self::Enum {
+                    variants,
+                    assume_padding_is_zeroed,
+                }
+                .intern_sized()
+            }
+            (Self::Enum { .. }, _) => unreachable!("mismatched types"),
+            (
+                Self::Bundle {
+                    fields: l_fields,
+                    assume_padding_is_zeroed: l_assume_padding_is_zeroed,
+                },
+                Self::Bundle {
+                    fields: r_fields,
+                    assume_padding_is_zeroed: r_assume_padding_is_zeroed,
+                },
+            ) => {
+                let fields = Interned::from_iter(
+                    l_fields
+                        .iter()
+                        .zip(&r_fields)
+                        .map(|(&l_field, &r_field)| l_field.merged(r_field)),
+                );
+                let assume_padding_is_zeroed =
+                    l_assume_padding_is_zeroed & r_assume_padding_is_zeroed;
+                Self::Bundle {
+                    fields,
+                    assume_padding_is_zeroed,
+                }
+                .intern_sized()
+            }
+            (Self::Bundle { .. }, _) => unreachable!("mismatched types"),
+            (Self::NoPadding, _) => {
+                unreachable!("NoPadding is always caught by the early return above")
+            }
+        }
+    }
+}
+
+#[derive(Copy, Clone)]
+enum ExprOrUnknown<T: Type> {
+    Expr(Expr<T>),
+    Unknown(T),
+}
+
+impl<T: Type> fmt::Debug for ExprOrUnknown<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Expr(expr) => expr.fmt(f),
+            Self::Unknown(ty) => f.debug_tuple("Unknown").field(ty).finish(),
+        }
+    }
+}
+
+fn write_expr_path(expr: impl ToExpr, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    write_expr_enum_path(&Expr::expr_enum(expr.to_expr()), f)
+}
+
+fn write_expr_enum_path(expr: &ExprEnum, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    fn fmt_target_base(
+        target_base: impl Into<TargetBase>,
+        f: &mut fmt::Formatter<'_>,
+    ) -> fmt::Result {
+        write!(f, "{:?}", target_base.into().target_name())
+    }
+    match expr {
+        ExprEnum::FieldAccess(expr) => {
+            write_expr_path(expr.base(), f)?;
+            write!(f, ".{}", expr.field_name())
+        }
+        ExprEnum::VariantAccess(expr) => {
+            write_expr_path(expr.base(), f)?;
+            write!(f, ".<{}>", expr.variant_name())
+        }
+        ExprEnum::ArrayIndex(expr) => {
+            write_expr_path(expr.base(), f)?;
+            write!(f, "[{}]", expr.element_index())
+        }
+        ExprEnum::DynArrayIndex(expr) => {
+            write_expr_path(expr.base(), f)?;
+            write!(f, "[...]")
+        }
+        ExprEnum::ToTraceAsString(expr) => {
+            write_expr_path(expr.inner(), f)?;
+            write!(f, ".to_trace_as_string()")
+        }
+        ExprEnum::TraceAsStringAsInner(expr) => {
+            write_expr_path(expr.arg(), f)?;
+            write!(f, ".<inner>")
+        }
+        ExprEnum::ModuleIO(expr) => fmt_target_base(*expr, f),
+        ExprEnum::Instance(expr) => fmt_target_base(*expr, f),
+        ExprEnum::Wire(expr) => fmt_target_base(*expr, f),
+        ExprEnum::Reg(expr) => fmt_target_base(*expr, f),
+        ExprEnum::RegSync(expr) => fmt_target_base(*expr, f),
+        ExprEnum::RegAsync(expr) => fmt_target_base(*expr, f),
+        ExprEnum::MemPort(expr) => fmt_target_base(*expr, f),
+        ExprEnum::FormalInput(expr) => fmt_target_base(*expr, f),
+
+        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::ReduceBitAndU(_)
+        | ExprEnum::ReduceBitAndS(_)
+        | ExprEnum::ReduceBitOrU(_)
+        | ExprEnum::ReduceBitOrS(_)
+        | ExprEnum::ReduceBitXorU(_)
+        | ExprEnum::ReduceBitXorS(_)
+        | ExprEnum::SliceUInt(_)
+        | ExprEnum::SliceSInt(_)
+        | ExprEnum::CastToBits(_)
+        | ExprEnum::CastBitsTo(_)
+        | ExprEnum::StructuralEq(_)
+        | ExprEnum::SimIoForGlobal(_) => write!(f, "..."),
+    }
+}
+
+fn display_expr_enum_path(expr: ExprEnum) -> impl fmt::Display {
+    fmt::from_fn(move |f| write_expr_enum_path(&expr, f))
+}
+
+fn display_expr_path(expr: impl ToExpr) -> impl fmt::Display {
+    display_expr_enum_path(*Expr::expr_enum(expr.to_expr()))
+}
+
+impl<T: Type> fmt::Display for ExprOrUnknown<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fn fmt_target_base(
+            target_base: impl Into<TargetBase>,
+            f: &mut fmt::Formatter<'_>,
+        ) -> fmt::Result {
+            write!(f, "{:?}", target_base.into().target_name())
+        }
+        match *self {
+            Self::Expr(expr) => match *Expr::expr_enum(expr) {
+                ExprEnum::FieldAccess(expr) => {
+                    ExprOrUnknown::Expr(expr.base()).fmt(f)?;
+                    write!(f, ".{}", expr.field_name())
+                }
+                ExprEnum::VariantAccess(expr) => {
+                    ExprOrUnknown::Expr(expr.base()).fmt(f)?;
+                    write!(f, ".<{}>", expr.variant_name())
+                }
+                ExprEnum::ArrayIndex(expr) => {
+                    ExprOrUnknown::Expr(expr.base()).fmt(f)?;
+                    write!(f, "[{}]", expr.element_index())
+                }
+                ExprEnum::DynArrayIndex(expr) => {
+                    ExprOrUnknown::Expr(expr.base()).fmt(f)?;
+                    write!(f, "[...]")
+                }
+                ExprEnum::ToTraceAsString(expr) => {
+                    ExprOrUnknown::Expr(expr.inner()).fmt(f)?;
+                    write!(f, ".to_trace_as_string()")
+                }
+                ExprEnum::TraceAsStringAsInner(expr) => {
+                    ExprOrUnknown::Expr(expr.arg()).fmt(f)?;
+                    write!(f, ".<inner>")
+                }
+                ExprEnum::ModuleIO(expr) => fmt_target_base(expr, f),
+                ExprEnum::Instance(expr) => fmt_target_base(expr, f),
+                ExprEnum::Wire(expr) => fmt_target_base(expr, f),
+                ExprEnum::Reg(expr) => fmt_target_base(expr, f),
+                ExprEnum::RegSync(expr) => fmt_target_base(expr, f),
+                ExprEnum::RegAsync(expr) => fmt_target_base(expr, f),
+                ExprEnum::MemPort(expr) => fmt_target_base(expr, f),
+                ExprEnum::FormalInput(expr) => fmt_target_base(expr, f),
+
+                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::ReduceBitAndU(_)
+                | ExprEnum::ReduceBitAndS(_)
+                | ExprEnum::ReduceBitOrU(_)
+                | ExprEnum::ReduceBitOrS(_)
+                | ExprEnum::ReduceBitXorU(_)
+                | ExprEnum::ReduceBitXorS(_)
+                | ExprEnum::SliceUInt(_)
+                | ExprEnum::SliceSInt(_)
+                | ExprEnum::CastToBits(_)
+                | ExprEnum::CastBitsTo(_)
+                | ExprEnum::StructuralEq(_)
+                | ExprEnum::SimIoForGlobal(_) => write!(f, "..."),
+            },
+            Self::Unknown(_ty) => write!(f, "Unknown(...)"),
+        }
+    }
+}
+
+impl<T: Type> From<Expr<T>> for ExprOrUnknown<T> {
+    fn from(expr: Expr<T>) -> Self {
+        Self::Expr(expr)
+    }
+}
+
+impl<T: Type> ExprOrUnknown<T> {
+    fn ty(self) -> T {
+        match self {
+            Self::Expr(expr) => expr.ty(),
+            Self::Unknown(ty) => ty,
+        }
+    }
+    fn map<U: Type>(
+        self,
+        map_ty: impl FnOnce(T) -> U,
+        map_expr: impl FnOnce(Expr<T>) -> Expr<U>,
+    ) -> ExprOrUnknown<U> {
+        match self {
+            Self::Expr(expr) => ExprOrUnknown::Expr(map_expr(expr)),
+            Self::Unknown(ty) => ExprOrUnknown::Unknown(map_ty(ty)),
+        }
+    }
+    fn from_canonical(v: ExprOrUnknown<CanonicalType>) -> Self {
+        match v {
+            ExprOrUnknown::Expr(expr) => Self::Expr(Expr::from_canonical(expr)),
+            ExprOrUnknown::Unknown(ty) => Self::Unknown(T::from_canonical(ty)),
+        }
+    }
+}
+
+impl ExprOrUnknown<Bundle> {
+    fn field_at_index(self, field_index: usize) -> ExprOrUnknown<CanonicalType> {
+        self.map(
+            |ty| ty.fields()[field_index].ty,
+            |expr| FieldAccess::new_by_index(expr, field_index).to_expr(),
+        )
+    }
+}
+
+impl ExprOrUnknown<Enum> {
+    fn variant_at_index(self, variant_index: usize) -> Option<ExprOrUnknown<CanonicalType>> {
+        match self {
+            Self::Expr(expr) => {
+                expr.ty().variants()[variant_index].ty?;
+                Some(ExprOrUnknown::Expr(
+                    VariantAccess::new_by_index(expr, variant_index).to_expr(),
+                ))
+            }
+            Self::Unknown(ty) => Some(ExprOrUnknown::Unknown(ty.variants()[variant_index].ty?)),
+        }
+    }
+}
+
+impl ExprOrUnknown<Array> {
+    fn element(self, element_index: usize) -> ExprOrUnknown<CanonicalType> {
+        match self {
+            Self::Expr(expr) => ExprOrUnknown::Expr(ArrayIndex::new(expr, element_index).to_expr()),
+            Self::Unknown(ty) => ExprOrUnknown::Unknown(ty.element()),
+        }
+    }
+}
+
+impl ExprOrUnknown<TraceAsString> {
+    fn inner(self) -> ExprOrUnknown<CanonicalType> {
+        match self {
+            Self::Expr(expr) => ExprOrUnknown::Expr(TraceAsStringAsInner::new(expr).to_expr()),
+            Self::Unknown(ty) => ExprOrUnknown::Unknown(ty.inner_ty()),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct State {
+    root_module: Interned<Module<Bundle>>,
+    debug_trace: bool,
+    any_changes: bool,
+    expr_flags: UnionFindMap<Interned<ExprEnum>, Interned<FlagsTree>>,
+    exprs_visited: HashMap<Interned<ExprEnum>, bool>,
+    modules_visited: HashMap<Interned<Module<Bundle>>, bool>,
+}
+
+impl State {
+    fn new(root_module: Interned<Module<Bundle>>, debug_trace: bool) -> Self {
+        Self {
+            root_module,
+            debug_trace,
+            any_changes: false,
+            expr_flags: UnionFindMap::default(),
+            exprs_visited: HashMap::default(),
+            modules_visited: HashMap::default(),
+        }
+    }
+    fn merge_expr_flags(
+        &mut self,
+        expr: Interned<ExprEnum>,
+        new_flags: FlagsTree,
+    ) -> Interned<FlagsTree> {
+        match self.expr_flags.entry(expr) {
+            Entry::Vacant(entry) => {
+                let new_flags = new_flags.intern_sized();
+                entry.insert(new_flags);
+                self.any_changes = true;
+                new_flags
+            }
+            Entry::Occupied(mut entry) => {
+                let merged_flags = new_flags.merged(*entry.get());
+                if merged_flags != *entry.get() {
+                    if self.debug_trace {
+                        indented_println!(
+                            "merge_expr_flags({}):\n\
+                            old flags: {:#?}\n\
+                            new_flags: {new_flags:#?}\n\
+                            merged_flags: {merged_flags:#?}",
+                            display_expr_enum_path(*expr),
+                            entry.get(),
+                        );
+                    }
+                    self.any_changes = true;
+                } else if self.debug_trace {
+                    if *merged_flags != new_flags {
+                        indented_println!(
+                            "merge_expr_flags({}):\n\
+                            flags (unchanged): {:#?}\n\
+                            new_flags: {new_flags:#?}",
+                            display_expr_enum_path(*expr),
+                            entry.get(),
+                        );
+                    } else {
+                        indented_println!(
+                            "merge_expr_flags({}):\n\
+                            flags (unchanged): {:#?}",
+                            display_expr_enum_path(*expr),
+                            entry.get(),
+                        );
+                    }
+                }
+                entry.insert(merged_flags);
+                merged_flags
+            }
+        }
+    }
+    fn union_exprs(
+        &mut self,
+        expr1: Interned<ExprEnum>,
+        expr2: Interned<ExprEnum>,
+    ) -> Interned<FlagsTree> {
+        let (unioned, value) = self
+            .expr_flags
+            .union(&expr1, &expr2, |_, v1, _, v2| v1.merged(v2));
+        self.any_changes |= unioned;
+        *value
+    }
+    fn visit_expr_or_unknown(&mut self, expr: ExprOrUnknown<CanonicalType>) -> Interned<FlagsTree> {
+        match expr {
+            ExprOrUnknown::Expr(expr) => self.visit_canonical_expr(expr),
+            ExprOrUnknown::Unknown(ty) => FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: false,
+                },
+                self.debug_trace,
+            ),
+        }
+    }
+    fn connect(
+        &mut self,
+        lhs: impl Into<ExprOrUnknown<CanonicalType>>,
+        rhs: impl Into<ExprOrUnknown<CanonicalType>>,
+    ) -> (Interned<FlagsTree>, Interned<FlagsTree>) {
+        let lhs = lhs.into();
+        let rhs = rhs.into();
+        let _push_indent;
+        if self.debug_trace {
+            indented_println!("connect({lhs}, {rhs}):");
+            _push_indent = PushIndent::new();
+            indented_println!("lhs: {lhs:?}");
+            indented_println!("rhs: {rhs:?}");
+        }
+        let lhs_ty = lhs.ty();
+        let lhs_flags = self.visit_expr_or_unknown(lhs);
+        let rhs_flags = self.visit_expr_or_unknown(rhs);
+        if lhs_flags == rhs_flags {
+            return (lhs_flags, rhs_flags);
+        }
+        let (mut lhs_flags, mut rhs_flags) = match lhs_ty {
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_)
+            | CanonicalType::DynSimOnly(_) => {
+                unreachable!("flags are always FlagsTree::NoPadding")
+            }
+            CanonicalType::Array(lhs_ty) => {
+                let lhs = ExprOrUnknown::from_canonical(lhs);
+                let rhs = ExprOrUnknown::<Array>::from_canonical(rhs);
+                assert_eq!(lhs_ty.len(), rhs.ty().len());
+                assert!(lhs_ty.len() > 0);
+                // FlagsTree treats arrays transparently, so the returned flags don't need to be adjusted.
+                // All array indexing operations are unioned together so just arbitrarily use index 0
+                self.connect(lhs.element(0), rhs.element(0))
+            }
+            CanonicalType::Enum(lhs_ty) => {
+                let lhs = ExprOrUnknown::from_canonical(lhs);
+                let rhs = ExprOrUnknown::<Enum>::from_canonical(rhs);
+                assert_eq!(lhs_ty.variants().len(), rhs.ty().variants().len());
+                let mut lhs_assume_padding_is_zeroed =
+                    lhs_flags.assume_padding_is_zeroed() & rhs_flags.assume_padding_is_zeroed();
+                let mut lhs_variants = Vec::with_capacity(lhs_ty.variants().len());
+                for variant_index in 0..lhs_ty.variants().len() {
+                    let lhs_variant = lhs.variant_at_index(variant_index);
+                    let rhs_variant = rhs.variant_at_index(variant_index);
+                    assert_eq!(lhs_variant.is_some(), rhs_variant.is_some());
+                    if let Some(lhs_variant) = lhs_variant
+                        && let Some(rhs_variant) = rhs_variant
+                    {
+                        let (lhs_field_flags, _rhs_field_flags) =
+                            self.connect(lhs_variant, rhs_variant);
+                        lhs_variants.push(Some(lhs_field_flags));
+                        lhs_assume_padding_is_zeroed &= lhs_field_flags.assume_padding_is_zeroed();
+                    } else {
+                        lhs_variants.push(None);
+                    }
+                }
+                let lhs_flags = FlagsTree::Enum {
+                    variants: lhs_variants.intern_slice(),
+                    assume_padding_is_zeroed: lhs_assume_padding_is_zeroed,
+                }
+                .intern_sized();
+                (lhs_flags, rhs_flags)
+            }
+            CanonicalType::Bundle(lhs_ty) => {
+                let lhs = ExprOrUnknown::from_canonical(lhs);
+                let rhs = ExprOrUnknown::<Bundle>::from_canonical(rhs);
+                assert_eq!(lhs_ty.fields().len(), rhs.ty().fields().len());
+                let mut lhs_assume_padding_is_zeroed = lhs_flags.assume_padding_is_zeroed();
+                let mut rhs_assume_padding_is_zeroed = rhs_flags.assume_padding_is_zeroed();
+                let mut lhs_fields = Vec::with_capacity(lhs_ty.fields().len());
+                let mut rhs_fields = Vec::with_capacity(lhs_ty.fields().len());
+                for (field_index, (lhs_field, rhs_field)) in lhs_ty
+                    .fields()
+                    .into_iter()
+                    .zip(rhs.ty().fields())
+                    .enumerate()
+                {
+                    assert_eq!(lhs_field.flipped, rhs_field.flipped);
+                    let lhs_field_flags;
+                    let rhs_field_flags;
+                    if lhs_field.flipped {
+                        // flipped, so exchange lhs/rhs when recursively calling connect
+                        (rhs_field_flags, lhs_field_flags) = self.connect(
+                            rhs.field_at_index(field_index),
+                            lhs.field_at_index(field_index),
+                        );
+                    } else {
+                        (lhs_field_flags, rhs_field_flags) = self.connect(
+                            lhs.field_at_index(field_index),
+                            rhs.field_at_index(field_index),
+                        );
+                    }
+                    lhs_fields.push(lhs_field_flags);
+                    rhs_fields.push(rhs_field_flags);
+                    lhs_assume_padding_is_zeroed &= lhs_field_flags.assume_padding_is_zeroed();
+                    rhs_assume_padding_is_zeroed &= rhs_field_flags.assume_padding_is_zeroed();
+                }
+                let lhs_flags = FlagsTree::Bundle {
+                    fields: lhs_fields.intern_slice(),
+                    assume_padding_is_zeroed: lhs_assume_padding_is_zeroed,
+                }
+                .intern_sized();
+                let rhs_flags = FlagsTree::Bundle {
+                    fields: rhs_fields.intern_slice(),
+                    assume_padding_is_zeroed: rhs_assume_padding_is_zeroed,
+                }
+                .intern_sized();
+                (lhs_flags, rhs_flags)
+            }
+            CanonicalType::TraceAsString(_) => {
+                let lhs = ExprOrUnknown::from_canonical(lhs);
+                let rhs = ExprOrUnknown::from_canonical(rhs);
+                // FlagsTree treats TraceAsString transparently, so the returned flags don't need to be adjusted.
+                // this expression and the inner expression are unioned together
+                self.connect(lhs.inner(), rhs.inner())
+            }
+        };
+        if let ExprOrUnknown::Expr(lhs) = lhs {
+            lhs_flags = self.merge_expr_flags(Expr::expr_enum(lhs), *lhs_flags);
+        }
+        if let ExprOrUnknown::Expr(rhs) = rhs {
+            rhs_flags = self.merge_expr_flags(Expr::expr_enum(rhs), *rhs_flags);
+        }
+        let retval = (lhs_flags, rhs_flags);
+        if self.debug_trace {
+            indented_println!("returned: {retval:#?}");
+        }
+        retval
+    }
+    fn visit_canonical_expr(&mut self, expr: Expr<CanonicalType>) -> Interned<FlagsTree> {
+        let expr_enum = Expr::expr_enum(expr);
+        let ty = expr.ty();
+        let visited = self.exprs_visited.entry(expr_enum).or_insert(false);
+        let flags = *self.expr_flags.entry(expr_enum).or_insert_with(|| {
+            self.any_changes = true;
+            FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: true,
+                },
+                self.debug_trace,
+            )
+        });
+        if std::mem::replace(visited, true) {
+            return flags;
+        }
+        let handle_array_index = |this: &mut Self, base: Expr<Array>| -> FlagsTree {
+            this.visit_canonical_expr(Expr::canonical(base));
+            // FlagsTree treats arrays transparently, so just union them together.
+            *this.union_exprs(Expr::expr_enum(base), expr_enum)
+        };
+        let handle_reg = |this: &mut Self, init: Option<Expr<CanonicalType>>| -> FlagsTree {
+            let init = match init {
+                Some(init) => ExprOrUnknown::Expr(init),
+                None => ExprOrUnknown::Unknown(ty),
+            };
+            let (flags, _) = this.connect(ExprOrUnknown::Expr(expr), init);
+            *flags
+        };
+        let literal_bits = expr_enum.to_literal_bits();
+        let flags = match *expr_enum {
+            _ if literal_bits.is_ok() => {
+                let Ok(bits) = &literal_bits else {
+                    unreachable!();
+                };
+                *FlagsTree::new(
+                    ty,
+                    FlagsTreeSourceValue::LiteralBits { bits },
+                    self.debug_trace,
+                )
+            }
+            ExprEnum::UIntLiteral(_)
+            | ExprEnum::SIntLiteral(_)
+            | ExprEnum::BoolLiteral(_)
+            | ExprEnum::PhantomConst(_) => *flags,
+            ExprEnum::BundleLiteral(bundle_literal) => {
+                let expr = Expr::<Bundle>::from_canonical(expr);
+                let ty = bundle_literal.ty();
+                let mut assume_padding_is_zeroed = flags.assume_padding_is_zeroed();
+                let mut fields = Vec::with_capacity(ty.fields().len());
+                for (field_index, field) in ty.fields().into_iter().enumerate() {
+                    assert!(!field.flipped);
+                    let (field_flags, _) = self.connect(
+                        FieldAccess::new_by_index(expr, field_index).to_expr(),
+                        bundle_literal.field_values()[field_index],
+                    );
+                    fields.push(field_flags);
+                    assume_padding_is_zeroed &= field_flags.assume_padding_is_zeroed();
+                }
+                if let FlagsTree::NoPadding = *flags {
+                    *flags
+                } else {
+                    FlagsTree::Bundle {
+                        fields: fields.intern_slice(),
+                        assume_padding_is_zeroed,
+                    }
+                }
+            }
+            ExprEnum::ArrayLiteral(array_literal) => {
+                let expr = Expr::<Array>::from_canonical(expr);
+                for (element_index, element_value) in
+                    array_literal.element_values().into_iter().enumerate()
+                {
+                    let array_index = ArrayIndex::new(expr, element_index).to_expr();
+                    self.visit_canonical_expr(array_index);
+                    self.union_exprs(expr_enum, Expr::expr_enum(array_index));
+                    self.connect(array_index, element_value);
+                }
+                *flags
+            }
+            ExprEnum::EnumLiteral(enum_literal) => {
+                let expr = Expr::<Enum>::from_canonical(expr);
+                let variant_access =
+                    VariantAccess::new_by_index(expr, enum_literal.variant_index()).to_expr();
+                self.visit_canonical_expr(variant_access);
+                if let Some(variant_value) = enum_literal.variant_value() {
+                    self.connect(variant_access, variant_value);
+                }
+                *flags
+            }
+            ExprEnum::Uninit(_) => *FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: false,
+                },
+                self.debug_trace,
+            ),
+            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(_) => *flags,
+            ExprEnum::FieldAccess(field_access) => {
+                let base_flags = self.visit_canonical_expr(Expr::canonical(field_access.base()));
+                match *base_flags {
+                    FlagsTree::Enum { .. } => unreachable!(),
+                    FlagsTree::Bundle {
+                        fields,
+                        assume_padding_is_zeroed,
+                    } => {
+                        let field_flags = fields[field_access.field_index()];
+                        let flags = field_flags.merged(flags);
+                        if flags != field_flags {
+                            self.merge_expr_flags(
+                                Expr::expr_enum(field_access.base()),
+                                FlagsTree::Bundle {
+                                    fields: fields
+                                        .iter()
+                                        .enumerate()
+                                        .map(|(i, field)| {
+                                            if i == field_access.field_index() {
+                                                flags
+                                            } else {
+                                                *field
+                                            }
+                                        })
+                                        .collect(),
+                                    assume_padding_is_zeroed: assume_padding_is_zeroed
+                                        & flags.assume_padding_is_zeroed(),
+                                },
+                            );
+                        }
+                        *flags
+                    }
+                    FlagsTree::NoPadding => *flags,
+                }
+            }
+            ExprEnum::VariantAccess(variant_access) => {
+                let base_flags = self.visit_canonical_expr(Expr::canonical(variant_access.base()));
+                match *base_flags {
+                    FlagsTree::Enum {
+                        variants,
+                        assume_padding_is_zeroed,
+                    } => {
+                        if let Some(variant_flags) = variants[variant_access.variant_index()] {
+                            let flags = variant_flags.merged(flags);
+                            if flags != variant_flags {
+                                self.merge_expr_flags(
+                                    Expr::expr_enum(variant_access.base()),
+                                    FlagsTree::Enum {
+                                        variants: variants
+                                            .iter()
+                                            .enumerate()
+                                            .map(|(i, field)| {
+                                                if i == variant_access.variant_index() {
+                                                    Some(flags)
+                                                } else {
+                                                    *field
+                                                }
+                                            })
+                                            .collect(),
+                                        assume_padding_is_zeroed: assume_padding_is_zeroed
+                                            & flags.assume_padding_is_zeroed(),
+                                    },
+                                );
+                            }
+                            *flags
+                        } else {
+                            *flags
+                        }
+                    }
+                    FlagsTree::Bundle { .. } => unreachable!(),
+                    FlagsTree::NoPadding => *flags,
+                }
+            }
+            ExprEnum::ArrayIndex(expr) => handle_array_index(self, expr.base()),
+            ExprEnum::DynArrayIndex(expr) => handle_array_index(self, expr.base()),
+            ExprEnum::ReduceBitAndU(_)
+            | ExprEnum::ReduceBitAndS(_)
+            | ExprEnum::ReduceBitOrU(_)
+            | ExprEnum::ReduceBitOrS(_)
+            | ExprEnum::ReduceBitXorU(_)
+            | ExprEnum::ReduceBitXorS(_)
+            | ExprEnum::SliceUInt(_)
+            | ExprEnum::SliceSInt(_)
+            | ExprEnum::CastToBits(_) => *flags,
+            ExprEnum::CastBitsTo(_) => *FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: false,
+                },
+                self.debug_trace,
+            ),
+            ExprEnum::ToTraceAsString(expr) => {
+                self.visit_canonical_expr(Expr::canonical(expr.inner()));
+                // FlagsTree treats TraceAsString transparently, so just union them together.
+                *self.union_exprs(Expr::expr_enum(expr.inner()), expr_enum)
+            }
+            ExprEnum::TraceAsStringAsInner(expr) => {
+                self.visit_canonical_expr(Expr::canonical(expr.arg()));
+                // FlagsTree treats TraceAsString transparently, so just union them together.
+                *self.union_exprs(Expr::expr_enum(expr.arg()), expr_enum)
+            }
+            ExprEnum::StructuralEq(_) => *flags,
+            ExprEnum::ModuleIO(_) => *flags,
+            ExprEnum::Instance(instance) => {
+                let expr = Expr::<Bundle>::from_canonical(expr);
+                for (field_index, module_io) in
+                    instance.instantiated().module_io().into_iter().enumerate()
+                {
+                    let module_io = module_io.module_io.to_expr();
+                    let field_access = FieldAccess::new_by_index(expr, field_index).to_expr();
+                    self.visit_canonical_expr(module_io);
+                    self.visit_canonical_expr(field_access);
+                    self.union_exprs(Expr::expr_enum(field_access), Expr::expr_enum(module_io));
+                }
+                *flags
+            }
+            ExprEnum::Wire(_) => *flags,
+            ExprEnum::Reg(reg) => handle_reg(self, reg.init()),
+            ExprEnum::RegSync(reg) => handle_reg(self, reg.init()),
+            ExprEnum::RegAsync(reg) => handle_reg(self, reg.init()),
+            ExprEnum::MemPort(_) => *FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: false,
+                },
+                self.debug_trace,
+            ),
+            ExprEnum::FormalInput(_) => *FlagsTree::new(
+                ty,
+                FlagsTreeSourceValue::Flags {
+                    assume_padding_is_zeroed: false,
+                },
+                self.debug_trace,
+            ),
+            ExprEnum::SimIoForGlobal(_) => {
+                unreachable!("Module is known to not contain SimIoForGlobal from validation")
+            }
+        };
+        self.merge_expr_flags(expr_enum, flags);
+        let Ok(()) = expr_enum.default_visit(self);
+        *self.expr_flags.find_mut(&expr_enum)
+    }
+}
+
+impl Visitor for State {
+    type Error = Infallible;
+
+    fn visit_expr_enum(&mut self, expr_enum: &ExprEnum) -> Result<(), Self::Error> {
+        self.visit_canonical_expr(expr_enum.to_expr());
+        Ok(())
+    }
+
+    fn visit_stmt_declaration(&mut self, stmt: &StmtDeclaration) -> Result<(), Self::Error> {
+        match stmt {
+            StmtDeclaration::Wire(StmtWire {
+                annotations: _,
+                wire,
+            }) => self.visit_canonical_expr(wire.to_expr()),
+            StmtDeclaration::Reg(StmtReg {
+                annotations: _,
+                reg,
+            }) => self.visit_canonical_expr(reg.to_expr()),
+            StmtDeclaration::RegSync(StmtReg {
+                annotations: _,
+                reg,
+            }) => self.visit_canonical_expr(reg.to_expr()),
+            StmtDeclaration::RegAsync(StmtReg {
+                annotations: _,
+                reg,
+            }) => self.visit_canonical_expr(reg.to_expr()),
+            StmtDeclaration::Instance(StmtInstance {
+                annotations: _,
+                instance,
+            }) => self.visit_canonical_expr(Expr::canonical(instance.to_expr())),
+        };
+        Ok(())
+    }
+
+    fn visit_stmt(&mut self, stmt: &Stmt) -> Result<(), Self::Error> {
+        match stmt {
+            &Stmt::Connect(StmtConnect {
+                lhs,
+                rhs,
+                source_location: _,
+            }) => {
+                self.connect(lhs, rhs);
+            }
+            Stmt::Formal(_) | Stmt::If(_) | Stmt::Match(_) => stmt.default_visit(self)?,
+            Stmt::Declaration(stmt) => self.visit_stmt_declaration(stmt)?,
+        }
+        Ok(())
+    }
+
+    fn visit_module<T: BundleType>(&mut self, module: &Module<T>) -> Result<(), Self::Error> {
+        let module = module.canonical().intern_sized();
+        let visited = self.modules_visited.entry(module).or_insert(false);
+        if std::mem::replace(visited, true) {
+            return Ok(());
+        }
+        let external = match module.body() {
+            ModuleBody::Normal(_) => false,
+            ModuleBody::Extern(_) => true,
+        };
+        let is_root_module = self.root_module == module;
+        if external || is_root_module {
+            for module_io in module.module_io() {
+                let expr = module_io.module_io.to_expr();
+                let mut connect_unknown = |is_lhs| {
+                    if is_lhs {
+                        self.connect(expr, ExprOrUnknown::Unknown(expr.ty()));
+                    } else {
+                        self.connect(ExprOrUnknown::Unknown(expr.ty()), expr);
+                    }
+                };
+                // all main/external module I/O can have non-zeroed padding
+                if external {
+                    // outputs are unknown
+                    connect_unknown(module_io.module_io.is_output());
+                }
+                // note: the root module can be external, so we don't use `else if` here
+                if is_root_module {
+                    // inputs are unknown
+                    connect_unknown(module_io.module_io.is_input());
+                }
+            }
+        }
+        module.default_visit(self)
+    }
+}
+
+impl Folder for State {
+    type Error = Infallible;
+    fn fold_structural_eq(&mut self, v: StructuralEq) -> Result<StructuralEq, Self::Error> {
+        let lhs_flags = *self.expr_flags.find_mut(&Expr::expr_enum(v.lhs()));
+        let rhs_flags = *self.expr_flags.find_mut(&Expr::expr_enum(v.rhs()));
+        let inputs_assume_padding_is_zeroed =
+            lhs_flags.assume_padding_is_zeroed() & rhs_flags.assume_padding_is_zeroed();
+        let new_lhs = v.lhs().fold(self)?;
+        let new_rhs = v.rhs().fold(self)?;
+        let StructuralEqFlags {
+            assume_padding_is_zeroed: orig_assume_padding_is_zeroed,
+        } = v.flags();
+        Ok(StructuralEq::with_flags(
+            new_lhs,
+            new_rhs,
+            StructuralEqFlags {
+                assume_padding_is_zeroed: inputs_assume_padding_is_zeroed
+                    | orig_assume_padding_is_zeroed,
+            },
+        ))
+    }
+}
+
+pub fn deduce_structural_eq_flags(module: Interned<Module<Bundle>>) -> Interned<Module<Bundle>> {
+    deduce_structural_eq_flags_with_debug_tracing(module, false)
+}
+
+pub fn deduce_structural_eq_flags_with_debug_tracing(
+    module: Interned<Module<Bundle>>,
+    debug_trace: bool,
+) -> Interned<Module<Bundle>> {
+    static CACHE: std::sync::Mutex<
+        Option<HashMap<Interned<Module<Bundle>>, Interned<Module<Bundle>>>>,
+    > = std::sync::Mutex::new(None);
+    let cache = CACHE.lock().expect("not poisoned");
+    if let Some(retval) = cache.as_ref().and_then(|cache| cache.get(&module)) {
+        return *retval;
+    }
+    drop(cache);
+    // the algorithm proceeds in two stages:
+    // 1. Visitor for State: a fixed-point data-flow algorithm to determine what flags should be
+    // 2. Folder for State: transforming the StructuralEq operations to have the deduced flags
+    let mut state = State::new(module, debug_trace);
+    let mut loops = 0;
+    const LOOP_LIMIT: u32 = 10000;
+    loop {
+        loops += 1;
+        let Ok(()) = module.visit(&mut state);
+        if loops > LOOP_LIMIT {
+            panic!("deduce_structural_eq_flags: looped too many times! state:\n{state:#?}");
+        }
+        let State {
+            root_module: _,
+            debug_trace: _,
+            any_changes,
+            expr_flags: _,
+            exprs_visited: expr_visited,
+            modules_visited: module_visited,
+        } = &mut state;
+        if !std::mem::replace(any_changes, false) {
+            break;
+        }
+        expr_visited.values_mut().for_each(|v| *v = false);
+        module_visited.values_mut().for_each(|v| *v = false);
+    }
+    if debug_trace {
+        indented_println!("{state:#?}");
+    }
+    let Ok(retval) = module.fold(&mut state);
+    CACHE
+        .lock()
+        .expect("not poisoned")
+        .get_or_insert_default()
+        .extend([(module, retval), (retval, retval)]);
+    retval
+}
diff --git a/crates/fayalite/src/module/transform/simplify_enums.rs b/crates/fayalite/src/module/transform/simplify_enums.rs
index 280701d..6c137ca 100644
--- a/crates/fayalite/src/module/transform/simplify_enums.rs
+++ b/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::{Bundle, BundleField, BundleType},
-    enum_::{Enum, EnumType, EnumVariant},
+    bundle::{BundleField, BundleType},
+    enum_::{EnumType, EnumVariant},
     expr::{
-        CastBitsTo, CastTo, CastToBits, Expr, ExprEnum, HdlPartialEq, ToExpr, ValueType,
-        ops::{self, EnumLiteral},
+        ExprEnum,
+        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,
-        transform::visit::{Fold, Folder},
+        Block, Id, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
+        transform::{
+            deduce_structural_eq_flags::deduce_structural_eq_flags,
+            visit::{Fold, Folder},
+        },
     },
-    source_location::SourceLocation,
-    ty::{CanonicalType, TraceAsString, Type},
+    prelude::*,
     util::HashMap,
-    wire::Wire,
 };
-use core::fmt;
 use serde::{Deserialize, Serialize};
+use std::fmt;
 
 #[derive(Debug)]
 pub enum SimplifyEnumsError {
@@ -97,6 +95,7 @@ enum EnumTypeState {
 struct ModuleState {
     module_name: NameId,
     expr_cache: HashMap<ExprEnum, ExprEnum>,
+    source_location: SourceLocation,
 }
 
 impl ModuleState {
@@ -110,6 +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 {
@@ -549,6 +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(
@@ -677,6 +894,7 @@ impl Folder for State {
         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();
@@ -710,6 +928,18 @@ impl Folder for State {
                     op.variant_index(),
                 )?)
             }
+            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)
@@ -837,11 +1067,13 @@ impl Folder for State {
     }
 
     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() {
@@ -867,7 +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!(
@@ -891,7 +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(),
@@ -906,10 +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),
@@ -1031,10 +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![],
     })
 }
diff --git a/crates/fayalite/src/phantom_const.rs b/crates/fayalite/src/phantom_const.rs
index ba85817..1552eab 100644
--- a/crates/fayalite/src/phantom_const.rs
+++ b/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,
diff --git a/crates/fayalite/src/sim/compiler.rs b/crates/fayalite/src/sim/compiler.rs
index c3c47fd..d82a540 100644
--- a/crates/fayalite/src/sim/compiler.rs
+++ b/crates/fayalite/src/sim/compiler.rs
@@ -3145,6 +3145,144 @@ impl Compiler {
             insns
         })
     }
+    fn compile_structural_eq(
+        &mut self,
+        instantiated_module_or_global: InstantiatedModuleOrGlobal,
+        expr: ops::StructuralEq,
+    ) -> CompiledExpr<CanonicalType> {
+        if expr.flags().assume_padding_is_zeroed {
+            return self.compile_expr(
+                instantiated_module_or_global,
+                Expr::canonical(expr.lhs().cast_to_bits().cmp_eq(expr.rhs().cast_to_bits())),
+            );
+        }
+        let source_location = instantiated_module_or_global.leaf_module_source_location();
+        match expr.lhs().ty() {
+            CanonicalType::UInt(_)
+            | CanonicalType::SInt(_)
+            | CanonicalType::Bool(_)
+            | CanonicalType::AsyncReset(_)
+            | CanonicalType::SyncReset(_)
+            | CanonicalType::Reset(_)
+            | CanonicalType::Clock(_)
+            | CanonicalType::PhantomConst(_) => self.compile_expr(
+                instantiated_module_or_global,
+                Expr::canonical(expr.lhs().cast_to_bits().cmp_eq(expr.rhs().cast_to_bits())),
+            ),
+            CanonicalType::Array(_) => {
+                let lhs = Expr::<Array>::from_canonical(expr.lhs());
+                let rhs = Expr::<Array>::from_canonical(expr.rhs());
+                self.compile_expr(
+                    instantiated_module_or_global,
+                    Expr::canonical(
+                        lhs.into_iter()
+                            .zip(rhs)
+                            .map(|(l, r)| {
+                                ops::StructuralEq::with_flags(l, r, expr.flags()).to_expr()
+                            })
+                            .reduce(|a, b| a & b)
+                            .unwrap_or_else(|| true.to_expr()),
+                    ),
+                )
+            }
+            CanonicalType::Enum(ty) => {
+                let lhs = self.compile_expr(instantiated_module_or_global, expr.lhs());
+                let lhs = self
+                    .compiled_expr_to_value(lhs, source_location)
+                    .map_ty(Enum::from_canonical);
+                let rhs = self.compile_expr(instantiated_module_or_global, expr.rhs());
+                let rhs = self
+                    .compiled_expr_to_value(rhs, source_location)
+                    .map_ty(Enum::from_canonical);
+                let lhs_discriminant = self.compile_enum_discriminant(lhs, source_location);
+                let rhs_discriminant = self.compile_enum_discriminant(rhs, source_location);
+                let retval = self.simple_nary_big_expr(
+                    instantiated_module_or_global,
+                    Bool.canonical(),
+                    [],
+                    |dest, []| {
+                        vec![Insn::Const {
+                            dest,
+                            value: BigInt::ZERO.intern_sized(),
+                        }]
+                    },
+                );
+                for variant_index in 0..ty.variants().len() {
+                    let variant_eq = self.compile_structural_eq(
+                        instantiated_module_or_global,
+                        ops::StructuralEq::with_flags(
+                            ops::VariantAccess::new_by_index(
+                                Expr::from_canonical(expr.lhs()),
+                                variant_index,
+                            )
+                            .to_expr(),
+                            ops::VariantAccess::new_by_index(
+                                Expr::from_canonical(expr.rhs()),
+                                variant_index,
+                            )
+                            .to_expr(),
+                            expr.flags(),
+                        ),
+                    );
+                    let variant_eq = self.compiled_expr_to_value(variant_eq, source_location);
+                    self.compile_simple_connect(
+                        [
+                            Cond {
+                                body: CondBody::MatchArm {
+                                    discriminant: lhs_discriminant,
+                                    variant_index,
+                                },
+                                source_location,
+                            },
+                            Cond {
+                                body: CondBody::MatchArm {
+                                    discriminant: rhs_discriminant,
+                                    variant_index,
+                                },
+                                source_location,
+                            },
+                        ]
+                        .intern_slice(),
+                        retval.into(),
+                        variant_eq,
+                        source_location,
+                    );
+                }
+                retval.into()
+            }
+            CanonicalType::Bundle(ty) => {
+                let lhs = Expr::<Bundle>::from_canonical(expr.lhs());
+                let rhs = Expr::<Bundle>::from_canonical(expr.rhs());
+                self.compile_expr(
+                    instantiated_module_or_global,
+                    Expr::canonical(
+                        (0..ty.fields().len())
+                            .map(|field_index| {
+                                ops::StructuralEq::with_flags(
+                                    ops::FieldAccess::new_by_index(lhs, field_index).to_expr(),
+                                    ops::FieldAccess::new_by_index(rhs, field_index).to_expr(),
+                                    expr.flags(),
+                                )
+                                .to_expr()
+                            })
+                            .reduce(|a, b| a & b)
+                            .unwrap_or_else(|| true.to_expr()),
+                    ),
+                )
+            }
+            CanonicalType::DynSimOnly(_) => {
+                unreachable!("StructuralEq is known to not have SimOnly in its inputs' types")
+            }
+            CanonicalType::TraceAsString(_) => {
+                let lhs = Expr::<TraceAsString>::from_canonical(expr.lhs());
+                let rhs = Expr::<TraceAsString>::from_canonical(expr.rhs());
+                self.compile_structural_eq(
+                    instantiated_module_or_global,
+                    ops::StructuralEq::with_flags(*lhs, *rhs, expr.flags()),
+                )
+            }
+        }
+    }
     fn compile_expr(
         &mut self,
         instantiated_module_or_global: impl Into<InstantiatedModuleOrGlobal>,
@@ -3974,6 +4112,9 @@ impl Compiler {
                 .compile_expr(instantiated_module_or_global, Expr::canonical(expr.arg()))
                 .map_ty(TraceAsString::from_canonical)
                 .inner(),
+            ExprEnum::StructuralEq(expr) => {
+                self.compile_structural_eq(instantiated_module_or_global, expr)
+            }
             ExprEnum::ModuleIO(expr) => self
                 .compile_value(TargetInInstantiatedModuleOrGlobal::from_target(
                     instantiated_module_or_global,
diff --git a/crates/fayalite/src/sim/value.rs b/crates/fayalite/src/sim/value.rs
index 24bc1ef..dd47633 100644
--- a/crates/fayalite/src/sim/value.rs
+++ b/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,
diff --git a/crates/fayalite/src/ty.rs b/crates/fayalite/src/ty.rs
index 843aedb..6505742 100644
--- a/crates/fayalite/src/ty.rs
+++ b/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 {
@@ -1882,6 +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,
diff --git a/crates/fayalite/src/util.rs b/crates/fayalite/src/util.rs
index 6845d3c..0e6723e 100644
--- a/crates/fayalite/src/util.rs
+++ b/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 HashSet<T> = hashbrown::HashSet<T, DefaultBuildHasher>;
+pub(crate) type HashMap<K, V, H = DefaultBuildHasher> = hashbrown::HashMap<K, V, H>;
+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;
diff --git a/crates/fayalite/src/util/bool_fixed_point_solver.rs b/crates/fayalite/src/util/bool_fixed_point_solver.rs
new file mode 100644
index 0000000..91119e9
--- /dev/null
+++ b/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);
+    }
+}
diff --git a/crates/fayalite/src/util/indented_print.rs b/crates/fayalite/src/util/indented_print.rs
new file mode 100644
index 0000000..7243578
--- /dev/null
+++ b/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;
diff --git a/crates/fayalite/src/util/map_trait.rs b/crates/fayalite/src/util/map_trait.rs
new file mode 100644
index 0000000..6fc065c
--- /dev/null
+++ b/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()
+        }
+    }
+}
diff --git a/crates/fayalite/src/util/union_find_map.rs b/crates/fayalite/src/util/union_find_map.rs
new file mode 100644
index 0000000..d197a61
--- /dev/null
+++ b/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(),
+        }
+    }
+}
diff --git a/crates/fayalite/tests/deduce_structural_eq_flags.rs b/crates/fayalite/tests/deduce_structural_eq_flags.rs
new file mode 100644
index 0000000..4633132
--- /dev/null
+++ b/crates/fayalite/tests/deduce_structural_eq_flags.rs
@@ -0,0 +1,4127 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+use fayalite::{
+    assert_export_firrtl,
+    expr::{ExprEnum, ops::StructuralEq, target::GetTarget},
+    firrtl::ExportOptions,
+    intern::Intern,
+    module::{
+        StmtConnect,
+        transform::{
+            deduce_structural_eq_flags::deduce_structural_eq_flags_with_debug_tracing,
+            simplify_enums::{SimplifyEnumsKind, simplify_enums},
+            visit::{Visit, Visitor},
+        },
+    },
+    prelude::*,
+};
+use std::convert::Infallible;
+
+#[hdl(outline_generated)]
+struct CheckStructuralEqOut {
+    opt_unit_flip: Bool,
+    opt_unit: Bool,
+    opt_bool_flip: Bool,
+    opt_bool: Bool,
+    opt_opt_unit_flip: Bool,
+    opt_opt_unit: Bool,
+    array_opt_bool_flip: Bool,
+    array_opt_bool: Bool,
+    struct_opt_bool_flip: Bool,
+    struct_opt_bool: Bool,
+}
+
+#[hdl(outline_generated)]
+struct CheckStructuralEqModuleIO {
+    #[hdl(flip)]
+    opt_unit_flip: HdlOption<()>,
+    opt_unit: HdlOption<()>,
+    #[hdl(flip)]
+    opt_bool_flip: HdlOption<Bool>,
+    opt_bool: HdlOption<Bool>,
+    #[hdl(flip)]
+    opt_opt_unit_flip: HdlOption<HdlOption<()>>,
+    opt_opt_unit: HdlOption<HdlOption<()>>,
+    #[hdl(flip)]
+    array_opt_bool_flip: Array<HdlOption<Bool>, 2>,
+    array_opt_bool: Array<HdlOption<Bool>, 2>,
+    #[hdl(flip)]
+    struct_opt_bool_flip: (HdlOption<Bool>, Bool),
+    struct_opt_bool: (HdlOption<Bool>, Bool),
+}
+
+#[hdl_module(extern, outline_generated)]
+fn check_deduce_structural_eq_flags_extern_child() {
+    #[hdl]
+    let io: CheckStructuralEqModuleIO = m.output();
+}
+
+#[hdl_module(outline_generated)]
+fn check_deduce_structural_eq_flags_child() {
+    #[hdl]
+    let io: CheckStructuralEqModuleIO = m.output();
+    #[hdl]
+    let CheckStructuralEqModuleIO {
+        opt_unit_flip,
+        opt_unit,
+        opt_bool_flip,
+        opt_bool,
+        opt_opt_unit_flip,
+        opt_opt_unit,
+        array_opt_bool_flip,
+        array_opt_bool,
+        struct_opt_bool_flip,
+        struct_opt_bool,
+    } = io;
+    connect(opt_unit, opt_unit_flip);
+    connect(opt_bool, opt_bool_flip);
+    connect(opt_opt_unit, opt_opt_unit_flip);
+    connect(array_opt_bool, array_opt_bool_flip);
+    connect(struct_opt_bool, struct_opt_bool_flip);
+}
+
+#[hdl_module(outline_generated)]
+fn check_deduce_structural_eq_flags_parent() {
+    #[hdl]
+    let io: CheckStructuralEqModuleIO = m.input();
+    #[hdl]
+    let io_zeros: CheckStructuralEqModuleIO = m.input();
+    #[hdl]
+    let io_alternating: CheckStructuralEqModuleIO = m.input();
+
+    #[hdl]
+    let parent_out: CheckStructuralEqOut = m.output();
+    #[hdl]
+    let parent_zeros_out: CheckStructuralEqOut = m.output();
+    #[hdl]
+    let parent_alternating_out: CheckStructuralEqOut = m.output();
+    #[hdl]
+    let extern_child_out: CheckStructuralEqOut = m.output();
+    #[hdl]
+    let child_out: CheckStructuralEqOut = m.output();
+
+    #[hdl]
+    let extern_child = instance(check_deduce_structural_eq_flags_extern_child());
+    #[hdl]
+    let child = instance(check_deduce_structural_eq_flags_child());
+
+    trait MapLiteral {
+        fn map_literal<T: Type>(&self, expr: impl ToExpr<Type = T>) -> Expr<T>;
+    }
+
+    impl<F: Fn(Expr<CanonicalType>) -> Expr<CanonicalType>> MapLiteral for F {
+        fn map_literal<T: Type>(&self, expr: impl ToExpr<Type = T>) -> Expr<T> {
+            Expr::from_canonical(self(Expr::canonical(expr.to_expr())))
+        }
+    }
+
+    #[hdl]
+    fn connect_io(
+        io_in: Expr<CheckStructuralEqModuleIO>,
+        out: Expr<CheckStructuralEqOut>,
+        map_literal: impl MapLiteral,
+    ) {
+        #[hdl]
+        let CheckStructuralEqModuleIO {
+            opt_unit_flip,
+            opt_unit,
+            opt_bool_flip,
+            opt_bool,
+            opt_opt_unit_flip,
+            opt_opt_unit,
+            array_opt_bool_flip,
+            array_opt_bool,
+            struct_opt_bool_flip,
+            struct_opt_bool,
+        } = io_in;
+        macro_rules! connect_pair {
+            ($field_flip:ident, $field:ident, $literal:expr $(,)?) => {
+                let literal = map_literal.map_literal($literal);
+                connect($field_flip, literal);
+                connect(
+                    out.$field,
+                    StructuralEq::new(Expr::canonical($field), Expr::canonical(literal)),
+                );
+                connect(
+                    out.$field_flip,
+                    StructuralEq::new(Expr::canonical($field_flip), Expr::canonical(literal)),
+                );
+            };
+        }
+        connect_pair!(opt_unit_flip, opt_unit, HdlSome(()));
+        connect_pair!(opt_bool_flip, opt_bool, HdlSome(true));
+        connect_pair!(opt_opt_unit_flip, opt_opt_unit, HdlSome(HdlSome(())));
+        connect_pair!(
+            array_opt_bool_flip,
+            array_opt_bool,
+            [HdlSome(false), HdlSome(true)],
+        );
+        connect_pair!(struct_opt_bool_flip, struct_opt_bool, (HdlSome(true), true));
+    };
+
+    connect_io(io, parent_out, |expr| expr);
+    connect_io(io_zeros, parent_zeros_out, |expr: Expr<CanonicalType>| {
+        let ty = expr.ty();
+        let bits = UInt[ty.bit_width()].zero().to_expr();
+        bits.cast_bits_to(ty)
+    });
+    connect_io(
+        io_alternating,
+        parent_alternating_out,
+        |expr: Expr<CanonicalType>| {
+            let ty = expr.ty();
+            let bits = u128::from_le_bytes([0xAA; _])
+                .cast_to(UInt[ty.bit_width()])
+                .to_expr();
+            bits.cast_bits_to(ty)
+        },
+    );
+    connect_io(extern_child.io, extern_child_out, |expr| expr);
+    connect_io(child.io, child_out, |expr| expr);
+}
+
+#[test]
+fn test_deduce_structural_eq_flags() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let m = check_deduce_structural_eq_flags_parent();
+    dbg!(m);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_structural_eq_flags_parent.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_structural_eq_flags_parent:
+    type Ty0 = {}
+    type Ty1 = {|HdlNone, HdlSome: Ty0|}
+    type Ty2 = {|HdlNone, HdlSome: UInt<1>|}
+    type Ty3 = {|HdlNone, HdlSome: Ty1|}
+    type Ty4 = {`0`: Ty2, `1`: UInt<1>}
+    type Ty5 = {flip opt_unit_flip: Ty1, opt_unit: Ty1, flip opt_bool_flip: Ty2, opt_bool: Ty2, flip opt_opt_unit_flip: Ty3, opt_opt_unit: Ty3, flip array_opt_bool_flip: Ty2[2], array_opt_bool: Ty2[2], flip struct_opt_bool_flip: Ty4, struct_opt_bool: Ty4}
+    type Ty6 = {opt_unit_flip: UInt<1>, opt_unit: UInt<1>, opt_bool_flip: UInt<1>, opt_bool: UInt<1>, opt_opt_unit_flip: UInt<1>, opt_opt_unit: UInt<1>, array_opt_bool_flip: UInt<1>, array_opt_bool: UInt<1>, struct_opt_bool_flip: UInt<1>, struct_opt_bool: UInt<1>}
+    type Ty7 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty8 = {io: Ty5}
+    module check_deduce_structural_eq_flags_parent: @[module-XXXXXXXXXX.rs 1:1]
+        input io: Ty5 @[module-XXXXXXXXXX.rs 2:1]
+        input io_zeros: Ty5 @[module-XXXXXXXXXX.rs 3:1]
+        input io_alternating: Ty5 @[module-XXXXXXXXXX.rs 4:1]
+        output parent_out: Ty6 @[module-XXXXXXXXXX.rs 5:1]
+        output parent_zeros_out: Ty6 @[module-XXXXXXXXXX.rs 6:1]
+        output parent_alternating_out: Ty6 @[module-XXXXXXXXXX.rs 7:1]
+        output extern_child_out: Ty6 @[module-XXXXXXXXXX.rs 8:1]
+        output child_out: Ty6 @[module-XXXXXXXXXX.rs 9:1]
+        inst extern_child of check_deduce_structural_eq_flags_extern_child @[module-XXXXXXXXXX.rs 10:1]
+        inst child of check_deduce_structural_eq_flags_child @[module-XXXXXXXXXX.rs 11:1]
+        wire _bundle_literal_expr: Ty0
+        invalidate _bundle_literal_expr
+        connect io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr: UInt<1>
+        match io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome):
+                connect _cast_enum_to_bits_expr, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        wire _cast_enum_to_bits_expr_1: UInt<1>
+        match {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_1, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_1):
+                connect _cast_enum_to_bits_expr_1, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_out.opt_unit, eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_2: UInt<1>
+        match io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_2, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_2):
+                connect _cast_enum_to_bits_expr_2, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_2, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_3: UInt<2>
+        match io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_3, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_3):
+                connect _cast_enum_to_bits_expr_3, pad(cat(_cast_enum_to_bits_expr_HdlSome_3, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_4: UInt<2>
+        match {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_4, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_4):
+                connect _cast_enum_to_bits_expr_4, pad(cat(_cast_enum_to_bits_expr_HdlSome_4, UInt<1>(1)), 2)
+        connect parent_out.opt_bool, eq(_cast_enum_to_bits_expr_3, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_5: UInt<2>
+        match io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_5, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_5):
+                connect _cast_enum_to_bits_expr_5, pad(cat(_cast_enum_to_bits_expr_HdlSome_5, UInt<1>(1)), 2)
+        connect parent_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_5, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_6: UInt<2>
+        match io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_6, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_6):
+                wire _cast_enum_to_bits_expr_7: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_6:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_7, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_7):
+                        connect _cast_enum_to_bits_expr_7, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_6, pad(cat(_cast_enum_to_bits_expr_7, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_8: UInt<2>
+        match {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_8, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_8):
+                wire _cast_enum_to_bits_expr_9: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_8:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_9, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_9):
+                        connect _cast_enum_to_bits_expr_9, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_8, pad(cat(_cast_enum_to_bits_expr_9, UInt<1>(1)), 2)
+        connect parent_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_6, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_10: UInt<2>
+        match io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_10, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_10):
+                wire _cast_enum_to_bits_expr_11: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_10:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_11, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_11):
+                        connect _cast_enum_to_bits_expr_11, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_10, pad(cat(_cast_enum_to_bits_expr_11, UInt<1>(1)), 2)
+        connect parent_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_10, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _array_literal_expr: Ty2[2]
+        connect _array_literal_expr[0], {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h0))
+        connect _array_literal_expr[1], {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1))
+        connect io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_12: UInt<2>
+        match io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_12, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_12):
+                connect _cast_enum_to_bits_expr_12, pad(cat(_cast_enum_to_bits_expr_HdlSome_12, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_13: UInt<2>
+        match _array_literal_expr[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_13, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_13):
+                connect _cast_enum_to_bits_expr_13, pad(cat(_cast_enum_to_bits_expr_HdlSome_13, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_14: UInt<2>
+        match io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_14, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_14):
+                connect _cast_enum_to_bits_expr_14, pad(cat(_cast_enum_to_bits_expr_HdlSome_14, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_15: UInt<2>
+        match _array_literal_expr[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_15, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_15):
+                connect _cast_enum_to_bits_expr_15, pad(cat(_cast_enum_to_bits_expr_HdlSome_15, UInt<1>(1)), 2)
+        wire _array_structural_eq: UInt<1>
+        connect _array_structural_eq, and(eq(_cast_enum_to_bits_expr_12, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_14, _cast_enum_to_bits_expr_15))
+        connect parent_out.array_opt_bool, _array_structural_eq @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_16: UInt<2>
+        match io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_16, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_16):
+                connect _cast_enum_to_bits_expr_16, pad(cat(_cast_enum_to_bits_expr_HdlSome_16, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_17: UInt<2>
+        match io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_17, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_17):
+                connect _cast_enum_to_bits_expr_17, pad(cat(_cast_enum_to_bits_expr_HdlSome_17, UInt<1>(1)), 2)
+        wire _array_structural_eq_1: UInt<1>
+        connect _array_structural_eq_1, and(eq(_cast_enum_to_bits_expr_16, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_17, _cast_enum_to_bits_expr_15))
+        connect parent_out.array_opt_bool_flip, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_literal_expr_1: Ty4
+        connect _bundle_literal_expr_1.`0`, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1))
+        connect _bundle_literal_expr_1.`1`, UInt<1>(0h1)
+        connect io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_18: UInt<2>
+        match io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_18, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_18):
+                connect _cast_enum_to_bits_expr_18, pad(cat(_cast_enum_to_bits_expr_HdlSome_18, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_19: UInt<2>
+        match _bundle_literal_expr_1.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_19, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_19):
+                connect _cast_enum_to_bits_expr_19, pad(cat(_cast_enum_to_bits_expr_HdlSome_19, UInt<1>(1)), 2)
+        wire _bundle_structural_eq: UInt<1>
+        connect _bundle_structural_eq, and(eq(_cast_enum_to_bits_expr_18, _cast_enum_to_bits_expr_19), eq(io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect parent_out.struct_opt_bool, _bundle_structural_eq @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_20: UInt<2>
+        match io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_20, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_20):
+                connect _cast_enum_to_bits_expr_20, pad(cat(_cast_enum_to_bits_expr_HdlSome_20, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_1: UInt<1>
+        connect _bundle_structural_eq_1, and(eq(_cast_enum_to_bits_expr_20, _cast_enum_to_bits_expr_19), eq(io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect parent_out.struct_opt_bool_flip, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_bits_to_enum_expr: Ty1
+        when eq(UInt<1>(0), tail(UInt<1>(0h0), 0)):
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+        else:
+            wire _cast_bits_to_bundle_expr: Ty0
+            invalidate _cast_bits_to_bundle_expr
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+        connect io_zeros.opt_unit_flip, _cast_bits_to_enum_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_21: UInt<1>
+        match io_zeros.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_21, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_21):
+                connect _cast_enum_to_bits_expr_21, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        wire _cast_enum_to_bits_expr_22: UInt<1>
+        match _cast_bits_to_enum_expr:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_22, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_22):
+                connect _cast_enum_to_bits_expr_22, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_zeros_out.opt_unit, eq(_cast_enum_to_bits_expr_21, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_23: UInt<1>
+        match io_zeros.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_23, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_23):
+                connect _cast_enum_to_bits_expr_23, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_zeros_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_23, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_enum_expr_1: Ty2
+        wire _cast_bits_to_enum_expr_body_1: UInt<1>
+        connect _cast_bits_to_enum_expr_body_1, head(UInt<2>(0h0), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h0), 1)):
+            connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_1)
+        connect io_zeros.opt_bool_flip, _cast_bits_to_enum_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_24: UInt<2>
+        match io_zeros.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_24, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_24):
+                connect _cast_enum_to_bits_expr_24, pad(cat(_cast_enum_to_bits_expr_HdlSome_24, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_25: UInt<2>
+        match _cast_bits_to_enum_expr_1:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_25, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_25):
+                connect _cast_enum_to_bits_expr_25, pad(cat(_cast_enum_to_bits_expr_HdlSome_25, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_bool, eq(_cast_enum_to_bits_expr_24, _cast_enum_to_bits_expr_25) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_26: UInt<2>
+        match io_zeros.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_26, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_26):
+                connect _cast_enum_to_bits_expr_26, pad(cat(_cast_enum_to_bits_expr_HdlSome_26, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_26, _cast_enum_to_bits_expr_25) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_bits_to_enum_expr_2: Ty3
+        wire _cast_bits_to_enum_expr_body_2: UInt<1>
+        connect _cast_bits_to_enum_expr_body_2, head(UInt<2>(0h0), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h0), 1)):
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome: Ty1|}(HdlNone)
+        else:
+            wire _cast_bits_to_enum_expr_3: Ty1
+            when eq(UInt<1>(0), tail(_cast_bits_to_enum_expr_body_2, 0)):
+                connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+            else:
+                connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome: Ty1|}(HdlSome, _cast_bits_to_enum_expr_3)
+        connect io_zeros.opt_opt_unit_flip, _cast_bits_to_enum_expr_2 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_27: UInt<2>
+        match io_zeros.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_27, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_27):
+                wire _cast_enum_to_bits_expr_28: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_27:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_28, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_28):
+                        connect _cast_enum_to_bits_expr_28, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_27, pad(cat(_cast_enum_to_bits_expr_28, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_29: UInt<2>
+        match _cast_bits_to_enum_expr_2:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_29, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_29):
+                wire _cast_enum_to_bits_expr_30: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_29:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_30, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_30):
+                        connect _cast_enum_to_bits_expr_30, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_29, pad(cat(_cast_enum_to_bits_expr_30, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_27, _cast_enum_to_bits_expr_29) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_31: UInt<2>
+        match io_zeros.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_31, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_31):
+                wire _cast_enum_to_bits_expr_32: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_31:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_32, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_32):
+                        connect _cast_enum_to_bits_expr_32, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_31, pad(cat(_cast_enum_to_bits_expr_32, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_31, _cast_enum_to_bits_expr_29) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened[0], bits(UInt<4>(0h0), 1, 0)
+        wire _cast_bits_to_enum_expr_4: Ty2
+        wire _cast_bits_to_enum_expr_body_4: UInt<1>
+        connect _cast_bits_to_enum_expr_body_4, head(_cast_bits_to_array_expr_flattened[0], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened[0], 1)):
+            connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_4)
+        connect _cast_bits_to_array_expr[0], _cast_bits_to_enum_expr_4
+        connect _cast_bits_to_array_expr_flattened[1], bits(UInt<4>(0h0), 3, 2)
+        wire _cast_bits_to_enum_expr_5: Ty2
+        wire _cast_bits_to_enum_expr_body_5: UInt<1>
+        connect _cast_bits_to_enum_expr_body_5, head(_cast_bits_to_array_expr_flattened[1], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened[1], 1)):
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_5)
+        connect _cast_bits_to_array_expr[1], _cast_bits_to_enum_expr_5
+        connect io_zeros.array_opt_bool_flip, _cast_bits_to_array_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_33: UInt<2>
+        match io_zeros.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_33, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_33):
+                connect _cast_enum_to_bits_expr_33, pad(cat(_cast_enum_to_bits_expr_HdlSome_33, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_34: UInt<2>
+        match _cast_bits_to_array_expr[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_34, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_34):
+                connect _cast_enum_to_bits_expr_34, pad(cat(_cast_enum_to_bits_expr_HdlSome_34, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_35: UInt<2>
+        match io_zeros.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_35, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_35):
+                connect _cast_enum_to_bits_expr_35, pad(cat(_cast_enum_to_bits_expr_HdlSome_35, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_36: UInt<2>
+        match _cast_bits_to_array_expr[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_36, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_36):
+                connect _cast_enum_to_bits_expr_36, pad(cat(_cast_enum_to_bits_expr_HdlSome_36, UInt<1>(1)), 2)
+        wire _array_structural_eq_2: UInt<1>
+        connect _array_structural_eq_2, and(eq(_cast_enum_to_bits_expr_33, _cast_enum_to_bits_expr_34), eq(_cast_enum_to_bits_expr_35, _cast_enum_to_bits_expr_36))
+        connect parent_zeros_out.array_opt_bool, _array_structural_eq_2 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_37: UInt<2>
+        match io_zeros.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_37, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_37):
+                connect _cast_enum_to_bits_expr_37, pad(cat(_cast_enum_to_bits_expr_HdlSome_37, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_38: UInt<2>
+        match io_zeros.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_38, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_38):
+                connect _cast_enum_to_bits_expr_38, pad(cat(_cast_enum_to_bits_expr_HdlSome_38, UInt<1>(1)), 2)
+        wire _array_structural_eq_3: UInt<1>
+        connect _array_structural_eq_3, and(eq(_cast_enum_to_bits_expr_37, _cast_enum_to_bits_expr_34), eq(_cast_enum_to_bits_expr_38, _cast_enum_to_bits_expr_36))
+        connect parent_zeros_out.array_opt_bool_flip, _array_structural_eq_3 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_1: Ty4
+        wire _cast_bits_to_bundle_expr_flattened: Ty7
+        connect _cast_bits_to_bundle_expr_flattened.`0`, bits(UInt<3>(0h0), 1, 0)
+        wire _cast_bits_to_enum_expr_6: Ty2
+        wire _cast_bits_to_enum_expr_body_6: UInt<1>
+        connect _cast_bits_to_enum_expr_body_6, head(_cast_bits_to_bundle_expr_flattened.`0`, 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened.`0`, 1)):
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_6)
+        connect _cast_bits_to_bundle_expr_1.`0`, _cast_bits_to_enum_expr_6
+        connect _cast_bits_to_bundle_expr_flattened.`1`, bits(UInt<3>(0h0), 2, 2)
+        connect _cast_bits_to_bundle_expr_1.`1`, _cast_bits_to_bundle_expr_flattened.`1`
+        connect io_zeros.struct_opt_bool_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_39: UInt<2>
+        match io_zeros.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_39, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_39):
+                connect _cast_enum_to_bits_expr_39, pad(cat(_cast_enum_to_bits_expr_HdlSome_39, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_40: UInt<2>
+        match _cast_bits_to_bundle_expr_1.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_40, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_40):
+                connect _cast_enum_to_bits_expr_40, pad(cat(_cast_enum_to_bits_expr_HdlSome_40, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_2: UInt<1>
+        connect _bundle_structural_eq_2, and(eq(_cast_enum_to_bits_expr_39, _cast_enum_to_bits_expr_40), eq(io_zeros.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_1.`1`))
+        connect parent_zeros_out.struct_opt_bool, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_41: UInt<2>
+        match io_zeros.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_41, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_41):
+                connect _cast_enum_to_bits_expr_41, pad(cat(_cast_enum_to_bits_expr_HdlSome_41, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_3: UInt<1>
+        connect _bundle_structural_eq_3, and(eq(_cast_enum_to_bits_expr_41, _cast_enum_to_bits_expr_40), eq(io_zeros.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_1.`1`))
+        connect parent_zeros_out.struct_opt_bool_flip, _bundle_structural_eq_3 @[module-XXXXXXXXXX.rs 17:1]
+        connect io_alternating.opt_unit_flip, _cast_bits_to_enum_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_42: UInt<1>
+        match io_alternating.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_42, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_42):
+                connect _cast_enum_to_bits_expr_42, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_alternating_out.opt_unit, eq(_cast_enum_to_bits_expr_42, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_43: UInt<1>
+        match io_alternating.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_43, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_43):
+                connect _cast_enum_to_bits_expr_43, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_alternating_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_43, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_enum_expr_7: Ty2
+        wire _cast_bits_to_enum_expr_body_7: UInt<1>
+        connect _cast_bits_to_enum_expr_body_7, head(UInt<2>(0h2), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h2), 1)):
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_7)
+        connect io_alternating.opt_bool_flip, _cast_bits_to_enum_expr_7 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_44: UInt<2>
+        match io_alternating.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_44, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_44):
+                connect _cast_enum_to_bits_expr_44, pad(cat(_cast_enum_to_bits_expr_HdlSome_44, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_45: UInt<2>
+        match _cast_bits_to_enum_expr_7:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_45, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_45):
+                connect _cast_enum_to_bits_expr_45, pad(cat(_cast_enum_to_bits_expr_HdlSome_45, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_bool, eq(_cast_enum_to_bits_expr_44, _cast_enum_to_bits_expr_45) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_46: UInt<2>
+        match io_alternating.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_46, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_46):
+                connect _cast_enum_to_bits_expr_46, pad(cat(_cast_enum_to_bits_expr_HdlSome_46, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_46, _cast_enum_to_bits_expr_45) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_bits_to_enum_expr_8: Ty3
+        wire _cast_bits_to_enum_expr_body_8: UInt<1>
+        connect _cast_bits_to_enum_expr_body_8, head(UInt<2>(0h2), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h2), 1)):
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome: Ty1|}(HdlNone)
+        else:
+            wire _cast_bits_to_enum_expr_9: Ty1
+            when eq(UInt<1>(0), tail(_cast_bits_to_enum_expr_body_8, 0)):
+                connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+            else:
+                connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome: Ty1|}(HdlSome, _cast_bits_to_enum_expr_9)
+        connect io_alternating.opt_opt_unit_flip, _cast_bits_to_enum_expr_8 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_47: UInt<2>
+        match io_alternating.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_47, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_47):
+                wire _cast_enum_to_bits_expr_48: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_47:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_48, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_48):
+                        connect _cast_enum_to_bits_expr_48, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_47, pad(cat(_cast_enum_to_bits_expr_48, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_49: UInt<2>
+        match _cast_bits_to_enum_expr_8:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_49, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_49):
+                wire _cast_enum_to_bits_expr_50: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_49:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_50, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_50):
+                        connect _cast_enum_to_bits_expr_50, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_49, pad(cat(_cast_enum_to_bits_expr_50, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_47, _cast_enum_to_bits_expr_49) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_51: UInt<2>
+        match io_alternating.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_51, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_51):
+                wire _cast_enum_to_bits_expr_52: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_51:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_52, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_52):
+                        connect _cast_enum_to_bits_expr_52, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_51, pad(cat(_cast_enum_to_bits_expr_52, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_51, _cast_enum_to_bits_expr_49) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr_1: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened_1: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened_1[0], bits(UInt<4>(0hA), 1, 0)
+        wire _cast_bits_to_enum_expr_10: Ty2
+        wire _cast_bits_to_enum_expr_body_10: UInt<1>
+        connect _cast_bits_to_enum_expr_body_10, head(_cast_bits_to_array_expr_flattened_1[0], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened_1[0], 1)):
+            connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_10)
+        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_enum_expr_10
+        connect _cast_bits_to_array_expr_flattened_1[1], bits(UInt<4>(0hA), 3, 2)
+        wire _cast_bits_to_enum_expr_11: Ty2
+        wire _cast_bits_to_enum_expr_body_11: UInt<1>
+        connect _cast_bits_to_enum_expr_body_11, head(_cast_bits_to_array_expr_flattened_1[1], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened_1[1], 1)):
+            connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_11)
+        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_enum_expr_11
+        connect io_alternating.array_opt_bool_flip, _cast_bits_to_array_expr_1 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_53: UInt<2>
+        match io_alternating.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_53, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_53):
+                connect _cast_enum_to_bits_expr_53, pad(cat(_cast_enum_to_bits_expr_HdlSome_53, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_54: UInt<2>
+        match _cast_bits_to_array_expr_1[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_54, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_54):
+                connect _cast_enum_to_bits_expr_54, pad(cat(_cast_enum_to_bits_expr_HdlSome_54, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_55: UInt<2>
+        match io_alternating.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_55, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_55):
+                connect _cast_enum_to_bits_expr_55, pad(cat(_cast_enum_to_bits_expr_HdlSome_55, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_56: UInt<2>
+        match _cast_bits_to_array_expr_1[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_56, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_56):
+                connect _cast_enum_to_bits_expr_56, pad(cat(_cast_enum_to_bits_expr_HdlSome_56, UInt<1>(1)), 2)
+        wire _array_structural_eq_4: UInt<1>
+        connect _array_structural_eq_4, and(eq(_cast_enum_to_bits_expr_53, _cast_enum_to_bits_expr_54), eq(_cast_enum_to_bits_expr_55, _cast_enum_to_bits_expr_56))
+        connect parent_alternating_out.array_opt_bool, _array_structural_eq_4 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_57: UInt<2>
+        match io_alternating.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_57, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_57):
+                connect _cast_enum_to_bits_expr_57, pad(cat(_cast_enum_to_bits_expr_HdlSome_57, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_58: UInt<2>
+        match io_alternating.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_58, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_58):
+                connect _cast_enum_to_bits_expr_58, pad(cat(_cast_enum_to_bits_expr_HdlSome_58, UInt<1>(1)), 2)
+        wire _array_structural_eq_5: UInt<1>
+        connect _array_structural_eq_5, and(eq(_cast_enum_to_bits_expr_57, _cast_enum_to_bits_expr_54), eq(_cast_enum_to_bits_expr_58, _cast_enum_to_bits_expr_56))
+        connect parent_alternating_out.array_opt_bool_flip, _array_structural_eq_5 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_2: Ty4
+        wire _cast_bits_to_bundle_expr_flattened_1: Ty7
+        connect _cast_bits_to_bundle_expr_flattened_1.`0`, bits(UInt<3>(0h2), 1, 0)
+        wire _cast_bits_to_enum_expr_12: Ty2
+        wire _cast_bits_to_enum_expr_body_12: UInt<1>
+        connect _cast_bits_to_enum_expr_body_12, head(_cast_bits_to_bundle_expr_flattened_1.`0`, 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_1.`0`, 1)):
+            connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_12)
+        connect _cast_bits_to_bundle_expr_2.`0`, _cast_bits_to_enum_expr_12
+        connect _cast_bits_to_bundle_expr_flattened_1.`1`, bits(UInt<3>(0h2), 2, 2)
+        connect _cast_bits_to_bundle_expr_2.`1`, _cast_bits_to_bundle_expr_flattened_1.`1`
+        connect io_alternating.struct_opt_bool_flip, _cast_bits_to_bundle_expr_2 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_59: UInt<2>
+        match io_alternating.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_59, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_59):
+                connect _cast_enum_to_bits_expr_59, pad(cat(_cast_enum_to_bits_expr_HdlSome_59, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_60: UInt<2>
+        match _cast_bits_to_bundle_expr_2.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_60, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_60):
+                connect _cast_enum_to_bits_expr_60, pad(cat(_cast_enum_to_bits_expr_HdlSome_60, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_4: UInt<1>
+        connect _bundle_structural_eq_4, and(eq(_cast_enum_to_bits_expr_59, _cast_enum_to_bits_expr_60), eq(io_alternating.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_2.`1`))
+        connect parent_alternating_out.struct_opt_bool, _bundle_structural_eq_4 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_61: UInt<2>
+        match io_alternating.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_61, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_61):
+                connect _cast_enum_to_bits_expr_61, pad(cat(_cast_enum_to_bits_expr_HdlSome_61, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_5: UInt<1>
+        connect _bundle_structural_eq_5, and(eq(_cast_enum_to_bits_expr_61, _cast_enum_to_bits_expr_60), eq(io_alternating.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_2.`1`))
+        connect parent_alternating_out.struct_opt_bool_flip, _bundle_structural_eq_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child.io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_62: UInt<1>
+        match extern_child.io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_62, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_62):
+                connect _cast_enum_to_bits_expr_62, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect extern_child_out.opt_unit, eq(_cast_enum_to_bits_expr_62, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_63: UInt<1>
+        match extern_child.io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_63, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_63):
+                connect _cast_enum_to_bits_expr_63, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect extern_child_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_63, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child.io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_64: UInt<2>
+        match extern_child.io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_64, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_64):
+                connect _cast_enum_to_bits_expr_64, pad(cat(_cast_enum_to_bits_expr_HdlSome_64, UInt<1>(1)), 2)
+        connect extern_child_out.opt_bool, eq(_cast_enum_to_bits_expr_64, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_65: UInt<2>
+        match extern_child.io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_65, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_65):
+                connect _cast_enum_to_bits_expr_65, pad(cat(_cast_enum_to_bits_expr_HdlSome_65, UInt<1>(1)), 2)
+        connect extern_child_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_65, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child.io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_66: UInt<2>
+        match extern_child.io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_66, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_66):
+                wire _cast_enum_to_bits_expr_67: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_66:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_67, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_67):
+                        connect _cast_enum_to_bits_expr_67, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_66, pad(cat(_cast_enum_to_bits_expr_67, UInt<1>(1)), 2)
+        connect extern_child_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_66, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_68: UInt<2>
+        match extern_child.io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_68, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_68):
+                wire _cast_enum_to_bits_expr_69: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_68:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_69, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_69):
+                        connect _cast_enum_to_bits_expr_69, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_68, pad(cat(_cast_enum_to_bits_expr_69, UInt<1>(1)), 2)
+        connect extern_child_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_68, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_70: UInt<2>
+        match extern_child.io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_70, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_70):
+                connect _cast_enum_to_bits_expr_70, pad(cat(_cast_enum_to_bits_expr_HdlSome_70, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_71: UInt<2>
+        match extern_child.io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_71, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_71):
+                connect _cast_enum_to_bits_expr_71, pad(cat(_cast_enum_to_bits_expr_HdlSome_71, UInt<1>(1)), 2)
+        wire _array_structural_eq_6: UInt<1>
+        connect _array_structural_eq_6, and(eq(_cast_enum_to_bits_expr_70, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_71, _cast_enum_to_bits_expr_15))
+        connect extern_child_out.array_opt_bool, _array_structural_eq_6 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_72: UInt<2>
+        match extern_child.io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_72, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_72):
+                connect _cast_enum_to_bits_expr_72, pad(cat(_cast_enum_to_bits_expr_HdlSome_72, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_73: UInt<2>
+        match extern_child.io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_73, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_73):
+                connect _cast_enum_to_bits_expr_73, pad(cat(_cast_enum_to_bits_expr_HdlSome_73, UInt<1>(1)), 2)
+        wire _array_structural_eq_7: UInt<1>
+        connect _array_structural_eq_7, and(eq(_cast_enum_to_bits_expr_72, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_73, _cast_enum_to_bits_expr_15))
+        connect extern_child_out.array_opt_bool_flip, _array_structural_eq_7 @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child.io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_74: UInt<2>
+        match extern_child.io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_74, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_74):
+                connect _cast_enum_to_bits_expr_74, pad(cat(_cast_enum_to_bits_expr_HdlSome_74, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_6: UInt<1>
+        connect _bundle_structural_eq_6, and(eq(_cast_enum_to_bits_expr_74, _cast_enum_to_bits_expr_19), eq(extern_child.io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect extern_child_out.struct_opt_bool, _bundle_structural_eq_6 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_75: UInt<2>
+        match extern_child.io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_75, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_75):
+                connect _cast_enum_to_bits_expr_75, pad(cat(_cast_enum_to_bits_expr_HdlSome_75, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_7: UInt<1>
+        connect _bundle_structural_eq_7, and(eq(_cast_enum_to_bits_expr_75, _cast_enum_to_bits_expr_19), eq(extern_child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect extern_child_out.struct_opt_bool_flip, _bundle_structural_eq_7 @[module-XXXXXXXXXX.rs 17:1]
+        connect child.io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_76: UInt<1>
+        match child.io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_76, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_76):
+                connect _cast_enum_to_bits_expr_76, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect child_out.opt_unit, eq(_cast_enum_to_bits_expr_76, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_77: UInt<1>
+        match child.io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_77, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_77):
+                connect _cast_enum_to_bits_expr_77, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect child_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_77, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect child.io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_78: UInt<2>
+        match child.io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_78, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_78):
+                connect _cast_enum_to_bits_expr_78, pad(cat(_cast_enum_to_bits_expr_HdlSome_78, UInt<1>(1)), 2)
+        connect child_out.opt_bool, eq(_cast_enum_to_bits_expr_78, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_79: UInt<2>
+        match child.io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_79, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_79):
+                connect _cast_enum_to_bits_expr_79, pad(cat(_cast_enum_to_bits_expr_HdlSome_79, UInt<1>(1)), 2)
+        connect child_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_79, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect child.io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_80: UInt<2>
+        match child.io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_80, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_80):
+                wire _cast_enum_to_bits_expr_81: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_80:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_81, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_81):
+                        connect _cast_enum_to_bits_expr_81, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_80, pad(cat(_cast_enum_to_bits_expr_81, UInt<1>(1)), 2)
+        connect child_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_80, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_82: UInt<2>
+        match child.io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_82, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_82):
+                wire _cast_enum_to_bits_expr_83: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_82:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_83, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_83):
+                        connect _cast_enum_to_bits_expr_83, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_82, pad(cat(_cast_enum_to_bits_expr_83, UInt<1>(1)), 2)
+        connect child_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_82, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        connect child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_84: UInt<2>
+        match child.io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_84, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_84):
+                connect _cast_enum_to_bits_expr_84, pad(cat(_cast_enum_to_bits_expr_HdlSome_84, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_85: UInt<2>
+        match child.io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_85, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_85):
+                connect _cast_enum_to_bits_expr_85, pad(cat(_cast_enum_to_bits_expr_HdlSome_85, UInt<1>(1)), 2)
+        wire _array_structural_eq_8: UInt<1>
+        connect _array_structural_eq_8, and(eq(_cast_enum_to_bits_expr_84, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_85, _cast_enum_to_bits_expr_15))
+        connect child_out.array_opt_bool, _array_structural_eq_8 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_86: UInt<2>
+        match child.io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_86, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_86):
+                connect _cast_enum_to_bits_expr_86, pad(cat(_cast_enum_to_bits_expr_HdlSome_86, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_87: UInt<2>
+        match child.io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_87, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_87):
+                connect _cast_enum_to_bits_expr_87, pad(cat(_cast_enum_to_bits_expr_HdlSome_87, UInt<1>(1)), 2)
+        wire _array_structural_eq_9: UInt<1>
+        connect _array_structural_eq_9, and(eq(_cast_enum_to_bits_expr_86, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_87, _cast_enum_to_bits_expr_15))
+        connect child_out.array_opt_bool_flip, _array_structural_eq_9 @[module-XXXXXXXXXX.rs 16:1]
+        connect child.io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_88: UInt<2>
+        match child.io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_88, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_88):
+                connect _cast_enum_to_bits_expr_88, pad(cat(_cast_enum_to_bits_expr_HdlSome_88, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_8: UInt<1>
+        connect _bundle_structural_eq_8, and(eq(_cast_enum_to_bits_expr_88, _cast_enum_to_bits_expr_19), eq(child.io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect child_out.struct_opt_bool, _bundle_structural_eq_8 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_89: UInt<2>
+        match child.io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_89, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_89):
+                connect _cast_enum_to_bits_expr_89, pad(cat(_cast_enum_to_bits_expr_HdlSome_89, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_9: UInt<1>
+        connect _bundle_structural_eq_9, and(eq(_cast_enum_to_bits_expr_89, _cast_enum_to_bits_expr_19), eq(child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect child_out.struct_opt_bool_flip, _bundle_structural_eq_9 @[module-XXXXXXXXXX.rs 17:1]
+    extmodule check_deduce_structural_eq_flags_extern_child: @[module-XXXXXXXXXX-2.rs 1:1]
+        output io: Ty5 @[module-XXXXXXXXXX-2.rs 2:1]
+        defname = check_deduce_structural_eq_flags_extern_child
+    module check_deduce_structural_eq_flags_child: @[module-XXXXXXXXXX-3.rs 1:1]
+        output io: Ty5 @[module-XXXXXXXXXX-3.rs 2:1]
+        connect io.opt_unit, io.opt_unit_flip @[module-XXXXXXXXXX-3.rs 4:1]
+        connect io.opt_bool, io.opt_bool_flip @[module-XXXXXXXXXX-3.rs 5:1]
+        connect io.opt_opt_unit, io.opt_opt_unit_flip @[module-XXXXXXXXXX-3.rs 6:1]
+        connect io.array_opt_bool, io.array_opt_bool_flip @[module-XXXXXXXXXX-3.rs 7:1]
+        connect io.struct_opt_bool, io.struct_opt_bool_flip @[module-XXXXXXXXXX-3.rs 8:1]
+",
+    };
+    let m = deduce_structural_eq_flags_with_debug_tracing(m.canonical().intern_sized(), true);
+    dbg!(m);
+    struct MyVisitor(Vec<(String, bool)>);
+    macro_rules! connects {
+        {$($key:literal: $value:literal),* $(,)?} => {
+            const KNOWN_CONNECTS: &[(&str, bool)] = &[$(($key, $value)),*];
+        };
+    }
+
+    connects! {
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_opt_unit": false,
+        "check_deduce_structural_eq_flags_parent::parent_out.opt_opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_out.array_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_out.array_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_out.struct_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_out.struct_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_opt_unit": false,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.opt_opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.array_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.array_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.struct_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_zeros_out.struct_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_bool_flip": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_opt_unit": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.opt_opt_unit_flip": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.array_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.array_opt_bool_flip": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.struct_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::parent_alternating_out.struct_opt_bool_flip": false,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_opt_unit": false,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.opt_opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.array_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.array_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.struct_opt_bool": false,
+        "check_deduce_structural_eq_flags_parent::extern_child_out.struct_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_bool": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_opt_unit": true,
+        "check_deduce_structural_eq_flags_parent::child_out.opt_opt_unit_flip": true,
+        "check_deduce_structural_eq_flags_parent::child_out.array_opt_bool": true,
+        "check_deduce_structural_eq_flags_parent::child_out.array_opt_bool_flip": true,
+        "check_deduce_structural_eq_flags_parent::child_out.struct_opt_bool": true,
+        "check_deduce_structural_eq_flags_parent::child_out.struct_opt_bool_flip": true,
+    }
+
+    impl Visitor for MyVisitor {
+        type Error = Infallible;
+        fn visit_stmt_connect(&mut self, v: &StmtConnect) -> Result<(), Self::Error> {
+            let ExprEnum::StructuralEq(structural_eq) = *Expr::expr_enum(v.rhs) else {
+                return v.default_visit(self);
+            };
+            let Some(lhs_target) = v.lhs.target() else {
+                panic!("connect lhs must have a Target: {v:#?}");
+            };
+            let lhs_target_str = lhs_target.to_string();
+            let assume_padding_is_zeroed = structural_eq.flags().assume_padding_is_zeroed;
+            if let Some(key) = KNOWN_CONNECTS
+                .iter()
+                .copied()
+                .find(|&(key, _)| key == lhs_target_str)
+            {
+                if assume_padding_is_zeroed != key.1 {
+                    println!("{key:?}: {v:#?}");
+                    panic!(
+                        "{key:?}: assume_padding_is_zeroed ({assume_padding_is_zeroed}) is not as expected"
+                    );
+                }
+            } else {
+                let k = (lhs_target_str, assume_padding_is_zeroed);
+                println!("{k:?}: {v:#?}");
+                self.0.push(k);
+            }
+            Ok(())
+        }
+    }
+    let mut visitor = MyVisitor(vec![]);
+    let Ok(()) = visitor.visit_module(&m);
+    if !visitor.0.is_empty() {
+        panic!(
+            "unknown connects:\nconnects! {:#?}",
+            std::fmt::from_fn(|f| { f.debug_map().entries(visitor.0.iter().cloned()).finish() })
+        )
+    }
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_structural_eq_flags_parent.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_structural_eq_flags_parent:
+    type Ty0 = {}
+    type Ty1 = {|HdlNone, HdlSome: Ty0|}
+    type Ty2 = {|HdlNone, HdlSome: UInt<1>|}
+    type Ty3 = {|HdlNone, HdlSome: Ty1|}
+    type Ty4 = {`0`: Ty2, `1`: UInt<1>}
+    type Ty5 = {flip opt_unit_flip: Ty1, opt_unit: Ty1, flip opt_bool_flip: Ty2, opt_bool: Ty2, flip opt_opt_unit_flip: Ty3, opt_opt_unit: Ty3, flip array_opt_bool_flip: Ty2[2], array_opt_bool: Ty2[2], flip struct_opt_bool_flip: Ty4, struct_opt_bool: Ty4}
+    type Ty6 = {opt_unit_flip: UInt<1>, opt_unit: UInt<1>, opt_bool_flip: UInt<1>, opt_bool: UInt<1>, opt_opt_unit_flip: UInt<1>, opt_opt_unit: UInt<1>, array_opt_bool_flip: UInt<1>, array_opt_bool: UInt<1>, struct_opt_bool_flip: UInt<1>, struct_opt_bool: UInt<1>}
+    type Ty7 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty8 = {io: Ty5}
+    module check_deduce_structural_eq_flags_parent: @[module-XXXXXXXXXX.rs 1:1]
+        input io: Ty5 @[module-XXXXXXXXXX.rs 2:1]
+        input io_zeros: Ty5 @[module-XXXXXXXXXX.rs 3:1]
+        input io_alternating: Ty5 @[module-XXXXXXXXXX.rs 4:1]
+        output parent_out: Ty6 @[module-XXXXXXXXXX.rs 5:1]
+        output parent_zeros_out: Ty6 @[module-XXXXXXXXXX.rs 6:1]
+        output parent_alternating_out: Ty6 @[module-XXXXXXXXXX.rs 7:1]
+        output extern_child_out: Ty6 @[module-XXXXXXXXXX.rs 8:1]
+        output child_out: Ty6 @[module-XXXXXXXXXX.rs 9:1]
+        inst extern_child of check_deduce_structural_eq_flags_extern_child @[module-XXXXXXXXXX.rs 10:1]
+        inst child of check_deduce_structural_eq_flags_child @[module-XXXXXXXXXX.rs 11:1]
+        wire _bundle_literal_expr: Ty0
+        invalidate _bundle_literal_expr
+        connect io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr: UInt<1>
+        match io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome):
+                connect _cast_enum_to_bits_expr, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        wire _cast_enum_to_bits_expr_1: UInt<1>
+        match {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_1, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_1):
+                connect _cast_enum_to_bits_expr_1, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_out.opt_unit, eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_2: UInt<1>
+        match io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_2, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_2):
+                connect _cast_enum_to_bits_expr_2, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_2, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_3: UInt<2>
+        match io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_3, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_3):
+                connect _cast_enum_to_bits_expr_3, pad(cat(_cast_enum_to_bits_expr_HdlSome_3, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_4: UInt<2>
+        match {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_4, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_4):
+                connect _cast_enum_to_bits_expr_4, pad(cat(_cast_enum_to_bits_expr_HdlSome_4, UInt<1>(1)), 2)
+        connect parent_out.opt_bool, eq(_cast_enum_to_bits_expr_3, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_5: UInt<2>
+        match io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_5, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_5):
+                connect _cast_enum_to_bits_expr_5, pad(cat(_cast_enum_to_bits_expr_HdlSome_5, UInt<1>(1)), 2)
+        connect parent_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_5, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_6: UInt<2>
+        match io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_6, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_6):
+                wire _cast_enum_to_bits_expr_7: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_6:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_7, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_7):
+                        connect _cast_enum_to_bits_expr_7, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_6, pad(cat(_cast_enum_to_bits_expr_7, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_8: UInt<2>
+        match {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)):
+            HdlNone:
+                connect _cast_enum_to_bits_expr_8, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_8):
+                wire _cast_enum_to_bits_expr_9: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_8:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_9, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_9):
+                        connect _cast_enum_to_bits_expr_9, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_8, pad(cat(_cast_enum_to_bits_expr_9, UInt<1>(1)), 2)
+        connect parent_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_6, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_10: UInt<2>
+        match io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_10, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_10):
+                wire _cast_enum_to_bits_expr_11: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_10:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_11, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_11):
+                        connect _cast_enum_to_bits_expr_11, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_10, pad(cat(_cast_enum_to_bits_expr_11, UInt<1>(1)), 2)
+        connect parent_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_10, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _array_literal_expr: Ty2[2]
+        connect _array_literal_expr[0], {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h0))
+        connect _array_literal_expr[1], {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1))
+        connect io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_12: UInt<2>
+        match io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_12, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_12):
+                connect _cast_enum_to_bits_expr_12, pad(cat(_cast_enum_to_bits_expr_HdlSome_12, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_13: UInt<2>
+        match _array_literal_expr[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_13, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_13):
+                connect _cast_enum_to_bits_expr_13, pad(cat(_cast_enum_to_bits_expr_HdlSome_13, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_14: UInt<2>
+        match io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_14, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_14):
+                connect _cast_enum_to_bits_expr_14, pad(cat(_cast_enum_to_bits_expr_HdlSome_14, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_15: UInt<2>
+        match _array_literal_expr[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_15, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_15):
+                connect _cast_enum_to_bits_expr_15, pad(cat(_cast_enum_to_bits_expr_HdlSome_15, UInt<1>(1)), 2)
+        wire _array_structural_eq: UInt<1>
+        connect _array_structural_eq, and(eq(_cast_enum_to_bits_expr_12, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_14, _cast_enum_to_bits_expr_15))
+        connect parent_out.array_opt_bool, _array_structural_eq @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_16: UInt<2>
+        match io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_16, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_16):
+                connect _cast_enum_to_bits_expr_16, pad(cat(_cast_enum_to_bits_expr_HdlSome_16, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_17: UInt<2>
+        match io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_17, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_17):
+                connect _cast_enum_to_bits_expr_17, pad(cat(_cast_enum_to_bits_expr_HdlSome_17, UInt<1>(1)), 2)
+        wire _array_structural_eq_1: UInt<1>
+        connect _array_structural_eq_1, and(eq(_cast_enum_to_bits_expr_16, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_17, _cast_enum_to_bits_expr_15))
+        connect parent_out.array_opt_bool_flip, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_literal_expr_1: Ty4
+        connect _bundle_literal_expr_1.`0`, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1))
+        connect _bundle_literal_expr_1.`1`, UInt<1>(0h1)
+        connect io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_18: UInt<2>
+        match io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_18, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_18):
+                connect _cast_enum_to_bits_expr_18, pad(cat(_cast_enum_to_bits_expr_HdlSome_18, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_19: UInt<2>
+        match _bundle_literal_expr_1.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_19, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_19):
+                connect _cast_enum_to_bits_expr_19, pad(cat(_cast_enum_to_bits_expr_HdlSome_19, UInt<1>(1)), 2)
+        wire _bundle_structural_eq: UInt<1>
+        connect _bundle_structural_eq, and(eq(_cast_enum_to_bits_expr_18, _cast_enum_to_bits_expr_19), eq(io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect parent_out.struct_opt_bool, _bundle_structural_eq @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_20: UInt<2>
+        match io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_20, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_20):
+                connect _cast_enum_to_bits_expr_20, pad(cat(_cast_enum_to_bits_expr_HdlSome_20, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_1: UInt<1>
+        connect _bundle_structural_eq_1, and(eq(_cast_enum_to_bits_expr_20, _cast_enum_to_bits_expr_19), eq(io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect parent_out.struct_opt_bool_flip, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_bits_to_enum_expr: Ty1
+        when eq(UInt<1>(0), tail(UInt<1>(0h0), 0)):
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+        else:
+            wire _cast_bits_to_bundle_expr: Ty0
+            invalidate _cast_bits_to_bundle_expr
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+        connect io_zeros.opt_unit_flip, _cast_bits_to_enum_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_21: UInt<1>
+        match io_zeros.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_21, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_21):
+                connect _cast_enum_to_bits_expr_21, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        wire _cast_enum_to_bits_expr_22: UInt<1>
+        match _cast_bits_to_enum_expr:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_22, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_22):
+                connect _cast_enum_to_bits_expr_22, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_zeros_out.opt_unit, eq(_cast_enum_to_bits_expr_21, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_23: UInt<1>
+        match io_zeros.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_23, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_23):
+                connect _cast_enum_to_bits_expr_23, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_zeros_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_23, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_enum_expr_1: Ty2
+        wire _cast_bits_to_enum_expr_body_1: UInt<1>
+        connect _cast_bits_to_enum_expr_body_1, head(UInt<2>(0h0), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h0), 1)):
+            connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_1, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_1)
+        connect io_zeros.opt_bool_flip, _cast_bits_to_enum_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_24: UInt<2>
+        match io_zeros.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_24, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_24):
+                connect _cast_enum_to_bits_expr_24, pad(cat(_cast_enum_to_bits_expr_HdlSome_24, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_25: UInt<2>
+        match _cast_bits_to_enum_expr_1:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_25, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_25):
+                connect _cast_enum_to_bits_expr_25, pad(cat(_cast_enum_to_bits_expr_HdlSome_25, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_bool, eq(_cast_enum_to_bits_expr_24, _cast_enum_to_bits_expr_25) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_26: UInt<2>
+        match io_zeros.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_26, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_26):
+                connect _cast_enum_to_bits_expr_26, pad(cat(_cast_enum_to_bits_expr_HdlSome_26, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_26, _cast_enum_to_bits_expr_25) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_bits_to_enum_expr_2: Ty3
+        wire _cast_bits_to_enum_expr_body_2: UInt<1>
+        connect _cast_bits_to_enum_expr_body_2, head(UInt<2>(0h0), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h0), 1)):
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome: Ty1|}(HdlNone)
+        else:
+            wire _cast_bits_to_enum_expr_3: Ty1
+            when eq(UInt<1>(0), tail(_cast_bits_to_enum_expr_body_2, 0)):
+                connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+            else:
+                connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome: Ty1|}(HdlSome, _cast_bits_to_enum_expr_3)
+        connect io_zeros.opt_opt_unit_flip, _cast_bits_to_enum_expr_2 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_27: UInt<2>
+        match io_zeros.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_27, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_27):
+                wire _cast_enum_to_bits_expr_28: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_27:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_28, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_28):
+                        connect _cast_enum_to_bits_expr_28, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_27, pad(cat(_cast_enum_to_bits_expr_28, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_29: UInt<2>
+        match _cast_bits_to_enum_expr_2:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_29, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_29):
+                wire _cast_enum_to_bits_expr_30: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_29:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_30, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_30):
+                        connect _cast_enum_to_bits_expr_30, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_29, pad(cat(_cast_enum_to_bits_expr_30, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_27, _cast_enum_to_bits_expr_29) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_31: UInt<2>
+        match io_zeros.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_31, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_31):
+                wire _cast_enum_to_bits_expr_32: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_31:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_32, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_32):
+                        connect _cast_enum_to_bits_expr_32, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_31, pad(cat(_cast_enum_to_bits_expr_32, UInt<1>(1)), 2)
+        connect parent_zeros_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_31, _cast_enum_to_bits_expr_29) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened[0], bits(UInt<4>(0h0), 1, 0)
+        wire _cast_bits_to_enum_expr_4: Ty2
+        wire _cast_bits_to_enum_expr_body_4: UInt<1>
+        connect _cast_bits_to_enum_expr_body_4, head(_cast_bits_to_array_expr_flattened[0], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened[0], 1)):
+            connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_4, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_4)
+        connect _cast_bits_to_array_expr[0], _cast_bits_to_enum_expr_4
+        connect _cast_bits_to_array_expr_flattened[1], bits(UInt<4>(0h0), 3, 2)
+        wire _cast_bits_to_enum_expr_5: Ty2
+        wire _cast_bits_to_enum_expr_body_5: UInt<1>
+        connect _cast_bits_to_enum_expr_body_5, head(_cast_bits_to_array_expr_flattened[1], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened[1], 1)):
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_5)
+        connect _cast_bits_to_array_expr[1], _cast_bits_to_enum_expr_5
+        connect io_zeros.array_opt_bool_flip, _cast_bits_to_array_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_33: UInt<2>
+        match io_zeros.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_33, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_33):
+                connect _cast_enum_to_bits_expr_33, pad(cat(_cast_enum_to_bits_expr_HdlSome_33, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_34: UInt<2>
+        match _cast_bits_to_array_expr[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_34, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_34):
+                connect _cast_enum_to_bits_expr_34, pad(cat(_cast_enum_to_bits_expr_HdlSome_34, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_35: UInt<2>
+        match io_zeros.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_35, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_35):
+                connect _cast_enum_to_bits_expr_35, pad(cat(_cast_enum_to_bits_expr_HdlSome_35, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_36: UInt<2>
+        match _cast_bits_to_array_expr[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_36, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_36):
+                connect _cast_enum_to_bits_expr_36, pad(cat(_cast_enum_to_bits_expr_HdlSome_36, UInt<1>(1)), 2)
+        wire _array_structural_eq_2: UInt<1>
+        connect _array_structural_eq_2, and(eq(_cast_enum_to_bits_expr_33, _cast_enum_to_bits_expr_34), eq(_cast_enum_to_bits_expr_35, _cast_enum_to_bits_expr_36))
+        connect parent_zeros_out.array_opt_bool, _array_structural_eq_2 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_37: UInt<2>
+        match io_zeros.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_37, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_37):
+                connect _cast_enum_to_bits_expr_37, pad(cat(_cast_enum_to_bits_expr_HdlSome_37, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_38: UInt<2>
+        match io_zeros.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_38, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_38):
+                connect _cast_enum_to_bits_expr_38, pad(cat(_cast_enum_to_bits_expr_HdlSome_38, UInt<1>(1)), 2)
+        wire _array_structural_eq_3: UInt<1>
+        connect _array_structural_eq_3, and(eq(_cast_enum_to_bits_expr_37, _cast_enum_to_bits_expr_34), eq(_cast_enum_to_bits_expr_38, _cast_enum_to_bits_expr_36))
+        connect parent_zeros_out.array_opt_bool_flip, _array_structural_eq_3 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_1: Ty4
+        wire _cast_bits_to_bundle_expr_flattened: Ty7
+        connect _cast_bits_to_bundle_expr_flattened.`0`, bits(UInt<3>(0h0), 1, 0)
+        wire _cast_bits_to_enum_expr_6: Ty2
+        wire _cast_bits_to_enum_expr_body_6: UInt<1>
+        connect _cast_bits_to_enum_expr_body_6, head(_cast_bits_to_bundle_expr_flattened.`0`, 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened.`0`, 1)):
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_6)
+        connect _cast_bits_to_bundle_expr_1.`0`, _cast_bits_to_enum_expr_6
+        connect _cast_bits_to_bundle_expr_flattened.`1`, bits(UInt<3>(0h0), 2, 2)
+        connect _cast_bits_to_bundle_expr_1.`1`, _cast_bits_to_bundle_expr_flattened.`1`
+        connect io_zeros.struct_opt_bool_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_39: UInt<2>
+        match io_zeros.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_39, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_39):
+                connect _cast_enum_to_bits_expr_39, pad(cat(_cast_enum_to_bits_expr_HdlSome_39, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_40: UInt<2>
+        match _cast_bits_to_bundle_expr_1.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_40, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_40):
+                connect _cast_enum_to_bits_expr_40, pad(cat(_cast_enum_to_bits_expr_HdlSome_40, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_2: UInt<1>
+        connect _bundle_structural_eq_2, and(eq(_cast_enum_to_bits_expr_39, _cast_enum_to_bits_expr_40), eq(io_zeros.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_1.`1`))
+        connect parent_zeros_out.struct_opt_bool, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_41: UInt<2>
+        match io_zeros.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_41, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_41):
+                connect _cast_enum_to_bits_expr_41, pad(cat(_cast_enum_to_bits_expr_HdlSome_41, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_3: UInt<1>
+        connect _bundle_structural_eq_3, and(eq(_cast_enum_to_bits_expr_41, _cast_enum_to_bits_expr_40), eq(io_zeros.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_1.`1`))
+        connect parent_zeros_out.struct_opt_bool_flip, _bundle_structural_eq_3 @[module-XXXXXXXXXX.rs 17:1]
+        connect io_alternating.opt_unit_flip, _cast_bits_to_enum_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_42: UInt<1>
+        match io_alternating.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_42, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_42):
+                connect _cast_enum_to_bits_expr_42, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_alternating_out.opt_unit, eq(_cast_enum_to_bits_expr_42, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_43: UInt<1>
+        match io_alternating.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_43, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_43):
+                connect _cast_enum_to_bits_expr_43, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect parent_alternating_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_43, _cast_enum_to_bits_expr_22) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_enum_expr_7: Ty2
+        wire _cast_bits_to_enum_expr_body_7: UInt<1>
+        connect _cast_bits_to_enum_expr_body_7, head(UInt<2>(0h2), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h2), 1)):
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_7)
+        connect io_alternating.opt_bool_flip, _cast_bits_to_enum_expr_7 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_44: UInt<2>
+        match io_alternating.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_44, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_44):
+                connect _cast_enum_to_bits_expr_44, pad(cat(_cast_enum_to_bits_expr_HdlSome_44, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_45: UInt<2>
+        match _cast_bits_to_enum_expr_7:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_45, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_45):
+                connect _cast_enum_to_bits_expr_45, pad(cat(_cast_enum_to_bits_expr_HdlSome_45, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_bool, eq(_cast_enum_to_bits_expr_44, _cast_enum_to_bits_expr_45) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_46: UInt<2>
+        match io_alternating.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_46, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_46):
+                connect _cast_enum_to_bits_expr_46, pad(cat(_cast_enum_to_bits_expr_HdlSome_46, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_46, _cast_enum_to_bits_expr_45) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_bits_to_enum_expr_8: Ty3
+        wire _cast_bits_to_enum_expr_body_8: UInt<1>
+        connect _cast_bits_to_enum_expr_body_8, head(UInt<2>(0h2), 1)
+        when eq(UInt<1>(0), tail(UInt<2>(0h2), 1)):
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome: Ty1|}(HdlNone)
+        else:
+            wire _cast_bits_to_enum_expr_9: Ty1
+            when eq(UInt<1>(0), tail(_cast_bits_to_enum_expr_body_8, 0)):
+                connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome: Ty0|}(HdlNone)
+            else:
+                connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome: Ty0|}(HdlSome, _cast_bits_to_bundle_expr)
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome: Ty1|}(HdlSome, _cast_bits_to_enum_expr_9)
+        connect io_alternating.opt_opt_unit_flip, _cast_bits_to_enum_expr_8 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_47: UInt<2>
+        match io_alternating.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_47, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_47):
+                wire _cast_enum_to_bits_expr_48: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_47:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_48, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_48):
+                        connect _cast_enum_to_bits_expr_48, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_47, pad(cat(_cast_enum_to_bits_expr_48, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_49: UInt<2>
+        match _cast_bits_to_enum_expr_8:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_49, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_49):
+                wire _cast_enum_to_bits_expr_50: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_49:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_50, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_50):
+                        connect _cast_enum_to_bits_expr_50, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_49, pad(cat(_cast_enum_to_bits_expr_50, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_47, _cast_enum_to_bits_expr_49) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_51: UInt<2>
+        match io_alternating.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_51, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_51):
+                wire _cast_enum_to_bits_expr_52: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_51:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_52, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_52):
+                        connect _cast_enum_to_bits_expr_52, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_51, pad(cat(_cast_enum_to_bits_expr_52, UInt<1>(1)), 2)
+        connect parent_alternating_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_51, _cast_enum_to_bits_expr_49) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr_1: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened_1: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened_1[0], bits(UInt<4>(0hA), 1, 0)
+        wire _cast_bits_to_enum_expr_10: Ty2
+        wire _cast_bits_to_enum_expr_body_10: UInt<1>
+        connect _cast_bits_to_enum_expr_body_10, head(_cast_bits_to_array_expr_flattened_1[0], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened_1[0], 1)):
+            connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_10)
+        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_enum_expr_10
+        connect _cast_bits_to_array_expr_flattened_1[1], bits(UInt<4>(0hA), 3, 2)
+        wire _cast_bits_to_enum_expr_11: Ty2
+        wire _cast_bits_to_enum_expr_body_11: UInt<1>
+        connect _cast_bits_to_enum_expr_body_11, head(_cast_bits_to_array_expr_flattened_1[1], 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_array_expr_flattened_1[1], 1)):
+            connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_11)
+        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_enum_expr_11
+        connect io_alternating.array_opt_bool_flip, _cast_bits_to_array_expr_1 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_53: UInt<2>
+        match io_alternating.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_53, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_53):
+                connect _cast_enum_to_bits_expr_53, pad(cat(_cast_enum_to_bits_expr_HdlSome_53, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_54: UInt<2>
+        match _cast_bits_to_array_expr_1[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_54, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_54):
+                connect _cast_enum_to_bits_expr_54, pad(cat(_cast_enum_to_bits_expr_HdlSome_54, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_55: UInt<2>
+        match io_alternating.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_55, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_55):
+                connect _cast_enum_to_bits_expr_55, pad(cat(_cast_enum_to_bits_expr_HdlSome_55, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_56: UInt<2>
+        match _cast_bits_to_array_expr_1[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_56, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_56):
+                connect _cast_enum_to_bits_expr_56, pad(cat(_cast_enum_to_bits_expr_HdlSome_56, UInt<1>(1)), 2)
+        wire _array_structural_eq_4: UInt<1>
+        connect _array_structural_eq_4, and(eq(_cast_enum_to_bits_expr_53, _cast_enum_to_bits_expr_54), eq(_cast_enum_to_bits_expr_55, _cast_enum_to_bits_expr_56))
+        connect parent_alternating_out.array_opt_bool, _array_structural_eq_4 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_57: UInt<2>
+        match io_alternating.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_57, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_57):
+                connect _cast_enum_to_bits_expr_57, pad(cat(_cast_enum_to_bits_expr_HdlSome_57, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_58: UInt<2>
+        match io_alternating.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_58, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_58):
+                connect _cast_enum_to_bits_expr_58, pad(cat(_cast_enum_to_bits_expr_HdlSome_58, UInt<1>(1)), 2)
+        wire _array_structural_eq_5: UInt<1>
+        connect _array_structural_eq_5, and(eq(_cast_enum_to_bits_expr_57, _cast_enum_to_bits_expr_54), eq(_cast_enum_to_bits_expr_58, _cast_enum_to_bits_expr_56))
+        connect parent_alternating_out.array_opt_bool_flip, _array_structural_eq_5 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_2: Ty4
+        wire _cast_bits_to_bundle_expr_flattened_1: Ty7
+        connect _cast_bits_to_bundle_expr_flattened_1.`0`, bits(UInt<3>(0h2), 1, 0)
+        wire _cast_bits_to_enum_expr_12: Ty2
+        wire _cast_bits_to_enum_expr_body_12: UInt<1>
+        connect _cast_bits_to_enum_expr_body_12, head(_cast_bits_to_bundle_expr_flattened_1.`0`, 1)
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_1.`0`, 1)):
+            connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome: UInt<1>|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, _cast_bits_to_enum_expr_body_12)
+        connect _cast_bits_to_bundle_expr_2.`0`, _cast_bits_to_enum_expr_12
+        connect _cast_bits_to_bundle_expr_flattened_1.`1`, bits(UInt<3>(0h2), 2, 2)
+        connect _cast_bits_to_bundle_expr_2.`1`, _cast_bits_to_bundle_expr_flattened_1.`1`
+        connect io_alternating.struct_opt_bool_flip, _cast_bits_to_bundle_expr_2 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_59: UInt<2>
+        match io_alternating.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_59, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_59):
+                connect _cast_enum_to_bits_expr_59, pad(cat(_cast_enum_to_bits_expr_HdlSome_59, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_60: UInt<2>
+        match _cast_bits_to_bundle_expr_2.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_60, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_60):
+                connect _cast_enum_to_bits_expr_60, pad(cat(_cast_enum_to_bits_expr_HdlSome_60, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_4: UInt<1>
+        connect _bundle_structural_eq_4, and(eq(_cast_enum_to_bits_expr_59, _cast_enum_to_bits_expr_60), eq(io_alternating.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_2.`1`))
+        connect parent_alternating_out.struct_opt_bool, _bundle_structural_eq_4 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_61: UInt<2>
+        match io_alternating.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_61, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_61):
+                connect _cast_enum_to_bits_expr_61, pad(cat(_cast_enum_to_bits_expr_HdlSome_61, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_5: UInt<1>
+        connect _bundle_structural_eq_5, and(eq(_cast_enum_to_bits_expr_61, _cast_enum_to_bits_expr_60), eq(io_alternating.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_2.`1`))
+        connect parent_alternating_out.struct_opt_bool_flip, _bundle_structural_eq_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child.io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_62: UInt<1>
+        match extern_child.io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_62, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_62):
+                connect _cast_enum_to_bits_expr_62, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect extern_child_out.opt_unit, eq(_cast_enum_to_bits_expr_62, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_63: UInt<1>
+        match extern_child.io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_63, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_63):
+                connect _cast_enum_to_bits_expr_63, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect extern_child_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_63, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child.io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_64: UInt<2>
+        match extern_child.io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_64, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_64):
+                connect _cast_enum_to_bits_expr_64, pad(cat(_cast_enum_to_bits_expr_HdlSome_64, UInt<1>(1)), 2)
+        connect extern_child_out.opt_bool, eq(_cast_enum_to_bits_expr_64, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_65: UInt<2>
+        match extern_child.io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_65, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_65):
+                connect _cast_enum_to_bits_expr_65, pad(cat(_cast_enum_to_bits_expr_HdlSome_65, UInt<1>(1)), 2)
+        connect extern_child_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_65, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child.io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_66: UInt<2>
+        match extern_child.io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_66, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_66):
+                wire _cast_enum_to_bits_expr_67: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_66:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_67, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_67):
+                        connect _cast_enum_to_bits_expr_67, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_66, pad(cat(_cast_enum_to_bits_expr_67, UInt<1>(1)), 2)
+        connect extern_child_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_66, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_68: UInt<2>
+        match extern_child.io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_68, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_68):
+                wire _cast_enum_to_bits_expr_69: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_68:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_69, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_69):
+                        connect _cast_enum_to_bits_expr_69, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_68, pad(cat(_cast_enum_to_bits_expr_69, UInt<1>(1)), 2)
+        connect extern_child_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_68, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_70: UInt<2>
+        match extern_child.io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_70, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_70):
+                connect _cast_enum_to_bits_expr_70, pad(cat(_cast_enum_to_bits_expr_HdlSome_70, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_71: UInt<2>
+        match extern_child.io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_71, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_71):
+                connect _cast_enum_to_bits_expr_71, pad(cat(_cast_enum_to_bits_expr_HdlSome_71, UInt<1>(1)), 2)
+        wire _array_structural_eq_6: UInt<1>
+        connect _array_structural_eq_6, and(eq(_cast_enum_to_bits_expr_70, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_71, _cast_enum_to_bits_expr_15))
+        connect extern_child_out.array_opt_bool, _array_structural_eq_6 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_72: UInt<2>
+        match extern_child.io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_72, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_72):
+                connect _cast_enum_to_bits_expr_72, pad(cat(_cast_enum_to_bits_expr_HdlSome_72, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_73: UInt<2>
+        match extern_child.io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_73, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_73):
+                connect _cast_enum_to_bits_expr_73, pad(cat(_cast_enum_to_bits_expr_HdlSome_73, UInt<1>(1)), 2)
+        wire _array_structural_eq_7: UInt<1>
+        connect _array_structural_eq_7, and(eq(_cast_enum_to_bits_expr_72, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_73, _cast_enum_to_bits_expr_15))
+        connect extern_child_out.array_opt_bool_flip, _array_structural_eq_7 @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child.io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_74: UInt<2>
+        match extern_child.io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_74, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_74):
+                connect _cast_enum_to_bits_expr_74, pad(cat(_cast_enum_to_bits_expr_HdlSome_74, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_6: UInt<1>
+        connect _bundle_structural_eq_6, and(eq(_cast_enum_to_bits_expr_74, _cast_enum_to_bits_expr_19), eq(extern_child.io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect extern_child_out.struct_opt_bool, _bundle_structural_eq_6 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_75: UInt<2>
+        match extern_child.io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_75, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_75):
+                connect _cast_enum_to_bits_expr_75, pad(cat(_cast_enum_to_bits_expr_HdlSome_75, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_7: UInt<1>
+        connect _bundle_structural_eq_7, and(eq(_cast_enum_to_bits_expr_75, _cast_enum_to_bits_expr_19), eq(extern_child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect extern_child_out.struct_opt_bool_flip, _bundle_structural_eq_7 @[module-XXXXXXXXXX.rs 17:1]
+        connect child.io.opt_unit_flip, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_76: UInt<1>
+        match child.io.opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_76, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_76):
+                connect _cast_enum_to_bits_expr_76, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect child_out.opt_unit, eq(_cast_enum_to_bits_expr_76, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_77: UInt<1>
+        match child.io.opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_77, UInt<1>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_77):
+                connect _cast_enum_to_bits_expr_77, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+        connect child_out.opt_unit_flip, eq(_cast_enum_to_bits_expr_77, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 13:1]
+        connect child.io.opt_bool_flip, {|HdlNone, HdlSome: UInt<1>|}(HdlSome, UInt<1>(0h1)) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_78: UInt<2>
+        match child.io.opt_bool:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_78, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_78):
+                connect _cast_enum_to_bits_expr_78, pad(cat(_cast_enum_to_bits_expr_HdlSome_78, UInt<1>(1)), 2)
+        connect child_out.opt_bool, eq(_cast_enum_to_bits_expr_78, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_79: UInt<2>
+        match child.io.opt_bool_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_79, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_79):
+                connect _cast_enum_to_bits_expr_79, pad(cat(_cast_enum_to_bits_expr_HdlSome_79, UInt<1>(1)), 2)
+        connect child_out.opt_bool_flip, eq(_cast_enum_to_bits_expr_79, _cast_enum_to_bits_expr_4) @[module-XXXXXXXXXX.rs 14:1]
+        connect child.io.opt_opt_unit_flip, {|HdlNone, HdlSome: Ty1|}(HdlSome, {|HdlNone, HdlSome: Ty0|}(HdlSome, _bundle_literal_expr)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_80: UInt<2>
+        match child.io.opt_opt_unit:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_80, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_80):
+                wire _cast_enum_to_bits_expr_81: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_80:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_81, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_81):
+                        connect _cast_enum_to_bits_expr_81, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_80, pad(cat(_cast_enum_to_bits_expr_81, UInt<1>(1)), 2)
+        connect child_out.opt_opt_unit, eq(_cast_enum_to_bits_expr_80, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_82: UInt<2>
+        match child.io.opt_opt_unit_flip:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_82, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_82):
+                wire _cast_enum_to_bits_expr_83: UInt<1>
+                match _cast_enum_to_bits_expr_HdlSome_82:
+                    HdlNone:
+                        connect _cast_enum_to_bits_expr_83, UInt<1>(0)
+                    HdlSome(_cast_enum_to_bits_expr_HdlSome_83):
+                        connect _cast_enum_to_bits_expr_83, pad(cat(UInt<0>(0), UInt<1>(1)), 1)
+                connect _cast_enum_to_bits_expr_82, pad(cat(_cast_enum_to_bits_expr_83, UInt<1>(1)), 2)
+        connect child_out.opt_opt_unit_flip, eq(_cast_enum_to_bits_expr_82, _cast_enum_to_bits_expr_8) @[module-XXXXXXXXXX.rs 15:1]
+        connect child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_84: UInt<2>
+        match child.io.array_opt_bool[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_84, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_84):
+                connect _cast_enum_to_bits_expr_84, pad(cat(_cast_enum_to_bits_expr_HdlSome_84, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_85: UInt<2>
+        match child.io.array_opt_bool[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_85, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_85):
+                connect _cast_enum_to_bits_expr_85, pad(cat(_cast_enum_to_bits_expr_HdlSome_85, UInt<1>(1)), 2)
+        wire _array_structural_eq_8: UInt<1>
+        connect _array_structural_eq_8, and(eq(_cast_enum_to_bits_expr_84, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_85, _cast_enum_to_bits_expr_15))
+        connect child_out.array_opt_bool, _array_structural_eq_8 @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_86: UInt<2>
+        match child.io.array_opt_bool_flip[0]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_86, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_86):
+                connect _cast_enum_to_bits_expr_86, pad(cat(_cast_enum_to_bits_expr_HdlSome_86, UInt<1>(1)), 2)
+        wire _cast_enum_to_bits_expr_87: UInt<2>
+        match child.io.array_opt_bool_flip[1]:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_87, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_87):
+                connect _cast_enum_to_bits_expr_87, pad(cat(_cast_enum_to_bits_expr_HdlSome_87, UInt<1>(1)), 2)
+        wire _array_structural_eq_9: UInt<1>
+        connect _array_structural_eq_9, and(eq(_cast_enum_to_bits_expr_86, _cast_enum_to_bits_expr_13), eq(_cast_enum_to_bits_expr_87, _cast_enum_to_bits_expr_15))
+        connect child_out.array_opt_bool_flip, _array_structural_eq_9 @[module-XXXXXXXXXX.rs 16:1]
+        connect child.io.struct_opt_bool_flip, _bundle_literal_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_88: UInt<2>
+        match child.io.struct_opt_bool.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_88, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_88):
+                connect _cast_enum_to_bits_expr_88, pad(cat(_cast_enum_to_bits_expr_HdlSome_88, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_8: UInt<1>
+        connect _bundle_structural_eq_8, and(eq(_cast_enum_to_bits_expr_88, _cast_enum_to_bits_expr_19), eq(child.io.struct_opt_bool.`1`, _bundle_literal_expr_1.`1`))
+        connect child_out.struct_opt_bool, _bundle_structural_eq_8 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_89: UInt<2>
+        match child.io.struct_opt_bool_flip.`0`:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_89, UInt<2>(0)
+            HdlSome(_cast_enum_to_bits_expr_HdlSome_89):
+                connect _cast_enum_to_bits_expr_89, pad(cat(_cast_enum_to_bits_expr_HdlSome_89, UInt<1>(1)), 2)
+        wire _bundle_structural_eq_9: UInt<1>
+        connect _bundle_structural_eq_9, and(eq(_cast_enum_to_bits_expr_89, _cast_enum_to_bits_expr_19), eq(child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_1.`1`))
+        connect child_out.struct_opt_bool_flip, _bundle_structural_eq_9 @[module-XXXXXXXXXX.rs 17:1]
+    extmodule check_deduce_structural_eq_flags_extern_child: @[module-XXXXXXXXXX-2.rs 1:1]
+        output io: Ty5 @[module-XXXXXXXXXX-2.rs 2:1]
+        defname = check_deduce_structural_eq_flags_extern_child
+    module check_deduce_structural_eq_flags_child: @[module-XXXXXXXXXX-3.rs 1:1]
+        output io: Ty5 @[module-XXXXXXXXXX-3.rs 2:1]
+        connect io.opt_unit, io.opt_unit_flip @[module-XXXXXXXXXX-3.rs 4:1]
+        connect io.opt_bool, io.opt_bool_flip @[module-XXXXXXXXXX-3.rs 5:1]
+        connect io.opt_opt_unit, io.opt_opt_unit_flip @[module-XXXXXXXXXX-3.rs 6:1]
+        connect io.array_opt_bool, io.array_opt_bool_flip @[module-XXXXXXXXXX-3.rs 7:1]
+        connect io.struct_opt_bool, io.struct_opt_bool_flip @[module-XXXXXXXXXX-3.rs 8:1]
+",
+    };
+    let m_no_body = simplify_enums(m, SimplifyEnumsKind::SimplifyToEnumsWithNoBody).unwrap();
+    dbg!(m_no_body);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m_no_body =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_structural_eq_flags_parent.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_structural_eq_flags_parent:
+    type Ty0 = {|HdlNone, HdlSome|}
+    type Ty1 = {tag: Ty0, body: UInt<0>}
+    type Ty2 = {tag: Ty0, body: UInt<1>}
+    type Ty3 = {`0`: Ty2, `1`: UInt<1>}
+    type Ty4 = {flip opt_unit_flip: Ty1, opt_unit: Ty1, flip opt_bool_flip: Ty2, opt_bool: Ty2, flip opt_opt_unit_flip: Ty2, opt_opt_unit: Ty2, flip array_opt_bool_flip: Ty2[2], array_opt_bool: Ty2[2], flip struct_opt_bool_flip: Ty3, struct_opt_bool: Ty3}
+    type Ty5 = {opt_unit_flip: UInt<1>, opt_unit: UInt<1>, opt_bool_flip: UInt<1>, opt_bool: UInt<1>, opt_opt_unit_flip: UInt<1>, opt_opt_unit: UInt<1>, array_opt_bool_flip: UInt<1>, array_opt_bool: UInt<1>, struct_opt_bool_flip: UInt<1>, struct_opt_bool: UInt<1>}
+    type Ty6 = {}
+    type Ty7 = {tag: UInt<1>, body: UInt<0>}
+    type Ty8 = {tag: UInt<1>, body: UInt<1>}
+    type Ty9 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty10 = {io: Ty4}
+    module check_deduce_structural_eq_flags_parent: @[module-XXXXXXXXXX.rs 1:1]
+        input io: Ty4 @[module-XXXXXXXXXX.rs 2:1]
+        input io_zeros: Ty4 @[module-XXXXXXXXXX.rs 3:1]
+        input io_alternating: Ty4 @[module-XXXXXXXXXX.rs 4:1]
+        output parent_out: Ty5 @[module-XXXXXXXXXX.rs 5:1]
+        output parent_zeros_out: Ty5 @[module-XXXXXXXXXX.rs 6:1]
+        output parent_alternating_out: Ty5 @[module-XXXXXXXXXX.rs 7:1]
+        output extern_child_out: Ty5 @[module-XXXXXXXXXX.rs 8:1]
+        output child_out: Ty5 @[module-XXXXXXXXXX.rs 9:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_1: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_2: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_3: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_4: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_5: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_6: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_7: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_8: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_9: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_10: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_11: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_12: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_13: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_14: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_15: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_16: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_17: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_18: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_19: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_20: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_21: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_22: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_23: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_24: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        inst extern_child of check_deduce_structural_eq_flags_extern_child @[module-XXXXXXXXXX.rs 10:1]
+        inst child of check_deduce_structural_eq_flags_child @[module-XXXXXXXXXX.rs 11:1]
+        wire _bundle_literal_expr: Ty1
+        connect _bundle_literal_expr.tag, {|HdlNone, HdlSome|}(HdlSome)
+        wire _bundle_literal_expr_1: Ty6
+        invalidate _bundle_literal_expr_1
+        connect _bundle_literal_expr.body, UInt<0>(0)
+        connect io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr: UInt<1>
+        match io.opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_1: UInt<1>
+        match _bundle_literal_expr.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_1, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_1, UInt<1>(1)
+        wire _bundle_structural_eq: UInt<1>
+        connect _bundle_structural_eq, and(eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1), eq(io.opt_unit.body, _bundle_literal_expr.body))
+        connect parent_out.opt_unit, _bundle_structural_eq @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_2: UInt<1>
+        match io.opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_2, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_2, UInt<1>(1)
+        wire _bundle_structural_eq_1: UInt<1>
+        connect _bundle_structural_eq_1, and(eq(_cast_enum_to_bits_expr_2, _cast_enum_to_bits_expr_1), eq(io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect parent_out.opt_unit_flip, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_literal_expr_2: Ty2
+        connect _bundle_literal_expr_2.tag, {|HdlNone, HdlSome|}(HdlSome)
+        connect _bundle_literal_expr_2.body, UInt<1>(0h1)
+        connect io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_out.opt_bool, __enum_structural_eq @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_3: UInt<1>
+        match io.opt_bool_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_3, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_3, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_4: UInt<1>
+        match _bundle_literal_expr_2.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_4, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_4, UInt<1>(1)
+        wire _bundle_structural_eq_2: UInt<1>
+        connect _bundle_structural_eq_2, and(eq(_cast_enum_to_bits_expr_3, _cast_enum_to_bits_expr_4), eq(io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect parent_out.opt_bool_flip, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_literal_expr_3: Ty2
+        connect _bundle_literal_expr_3.tag, {|HdlNone, HdlSome|}(HdlSome)
+        wire _cast_bundle_to_bits_expr: Ty7
+        connect _cast_bundle_to_bits_expr.tag, _cast_enum_to_bits_expr_1
+        connect _cast_bundle_to_bits_expr.body, _bundle_literal_expr.body
+        wire _cast_to_bits_expr: UInt<1>
+        connect _cast_to_bits_expr, cat(_cast_bundle_to_bits_expr.body, _cast_bundle_to_bits_expr.tag)
+        connect _bundle_literal_expr_3.body, _cast_to_bits_expr
+        connect io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_out.opt_opt_unit, __enum_structural_eq_1 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_5: UInt<1>
+        match io.opt_opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_5, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_5, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_6: UInt<1>
+        match _bundle_literal_expr_3.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_6, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_6, UInt<1>(1)
+        wire _bundle_structural_eq_3: UInt<1>
+        connect _bundle_structural_eq_3, and(eq(_cast_enum_to_bits_expr_5, _cast_enum_to_bits_expr_6), eq(io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect parent_out.opt_opt_unit_flip, _bundle_structural_eq_3 @[module-XXXXXXXXXX.rs 15:1]
+        wire _array_literal_expr: Ty2[2]
+        wire _bundle_literal_expr_4: Ty2
+        connect _bundle_literal_expr_4.tag, {|HdlNone, HdlSome|}(HdlSome)
+        connect _bundle_literal_expr_4.body, UInt<1>(0h0)
+        connect _array_literal_expr[0], _bundle_literal_expr_4
+        connect _array_literal_expr[1], _bundle_literal_expr_2
+        connect io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_out.array_opt_bool, and(__enum_structural_eq_2, __enum_structural_eq_3) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_7: UInt<1>
+        match io.array_opt_bool_flip[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_7, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_7, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_8: UInt<1>
+        match _array_literal_expr[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_8, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_8, UInt<1>(1)
+        wire _bundle_structural_eq_4: UInt<1>
+        connect _bundle_structural_eq_4, and(eq(_cast_enum_to_bits_expr_7, _cast_enum_to_bits_expr_8), eq(io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _cast_enum_to_bits_expr_9: UInt<1>
+        match io.array_opt_bool_flip[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_9, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_9, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_10: UInt<1>
+        match _array_literal_expr[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_10, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_10, UInt<1>(1)
+        wire _bundle_structural_eq_5: UInt<1>
+        connect _bundle_structural_eq_5, and(eq(_cast_enum_to_bits_expr_9, _cast_enum_to_bits_expr_10), eq(io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect parent_out.array_opt_bool_flip, and(_bundle_structural_eq_4, _bundle_structural_eq_5) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_literal_expr_5: Ty3
+        connect _bundle_literal_expr_5.`0`, _bundle_literal_expr_2
+        connect _bundle_literal_expr_5.`1`, UInt<1>(0h1)
+        connect io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_out.struct_opt_bool, and(__enum_structural_eq_4, eq(io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_11: UInt<1>
+        match io.struct_opt_bool_flip.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_11, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_11, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_12: UInt<1>
+        match _bundle_literal_expr_5.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_12, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_12, UInt<1>(1)
+        wire _bundle_structural_eq_6: UInt<1>
+        connect _bundle_structural_eq_6, and(eq(_cast_enum_to_bits_expr_11, _cast_enum_to_bits_expr_12), eq(io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect parent_out.struct_opt_bool_flip, and(_bundle_structural_eq_6, eq(io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_bits_to_bundle_expr: Ty1
+        wire _cast_bits_to_bundle_expr_flattened: Ty7
+        connect _cast_bits_to_bundle_expr_flattened.tag, bits(UInt<1>(0h0), 0, 0)
+        wire _cast_bits_to_enum_expr: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened.tag, 0)):
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr.tag, _cast_bits_to_enum_expr
+        connect _cast_bits_to_bundle_expr_flattened.body, UInt<0>(0)
+        connect _cast_bits_to_bundle_expr.body, _cast_bits_to_bundle_expr_flattened.body
+        connect io_zeros.opt_unit_flip, _cast_bits_to_bundle_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_13: UInt<1>
+        match io_zeros.opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_13, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_13, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_14: UInt<1>
+        match _cast_bits_to_bundle_expr.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_14, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_14, UInt<1>(1)
+        wire _bundle_structural_eq_7: UInt<1>
+        connect _bundle_structural_eq_7, and(eq(_cast_enum_to_bits_expr_13, _cast_enum_to_bits_expr_14), eq(io_zeros.opt_unit.body, _cast_bits_to_bundle_expr.body))
+        connect parent_zeros_out.opt_unit, _bundle_structural_eq_7 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_15: UInt<1>
+        match io_zeros.opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_15, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_15, UInt<1>(1)
+        wire _bundle_structural_eq_8: UInt<1>
+        connect _bundle_structural_eq_8, and(eq(_cast_enum_to_bits_expr_15, _cast_enum_to_bits_expr_14), eq(io_zeros.opt_unit_flip.body, _cast_bits_to_bundle_expr.body))
+        connect parent_zeros_out.opt_unit_flip, _bundle_structural_eq_8 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_bundle_expr_1: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_1: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(UInt<2>(0h0), 0, 0)
+        wire _cast_bits_to_enum_expr_1: Ty0
+        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(UInt<2>(0h0), 1, 1)
+        connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
+        connect io_zeros.opt_bool_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_zeros_out.opt_bool, __enum_structural_eq_5 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_16: UInt<1>
+        match io_zeros.opt_bool_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_16, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_16, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_17: UInt<1>
+        match _cast_bits_to_bundle_expr_1.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_17, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_17, UInt<1>(1)
+        wire _bundle_structural_eq_9: UInt<1>
+        connect _bundle_structural_eq_9, and(eq(_cast_enum_to_bits_expr_16, _cast_enum_to_bits_expr_17), eq(io_zeros.opt_bool_flip.body, _cast_bits_to_bundle_expr_1.body))
+        connect parent_zeros_out.opt_bool_flip, _bundle_structural_eq_9 @[module-XXXXXXXXXX.rs 14:1]
+        connect io_zeros.opt_opt_unit_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_zeros_out.opt_opt_unit, __enum_structural_eq_6 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_18: UInt<1>
+        match io_zeros.opt_opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_18, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_18, UInt<1>(1)
+        wire _bundle_structural_eq_10: UInt<1>
+        connect _bundle_structural_eq_10, and(eq(_cast_enum_to_bits_expr_18, _cast_enum_to_bits_expr_17), eq(io_zeros.opt_opt_unit_flip.body, _cast_bits_to_bundle_expr_1.body))
+        connect parent_zeros_out.opt_opt_unit_flip, _bundle_structural_eq_10 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened[0], bits(UInt<4>(0h0), 1, 0)
+        wire _cast_bits_to_bundle_expr_2: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_2: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(_cast_bits_to_array_expr_flattened[0], 0, 0)
+        wire _cast_bits_to_enum_expr_2: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_2.tag, 0)):
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_2, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_2.tag, _cast_bits_to_enum_expr_2
+        connect _cast_bits_to_bundle_expr_flattened_2.body, bits(_cast_bits_to_array_expr_flattened[0], 1, 1)
+        connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
+        connect _cast_bits_to_array_expr[0], _cast_bits_to_bundle_expr_2
+        connect _cast_bits_to_array_expr_flattened[1], bits(UInt<4>(0h0), 3, 2)
+        wire _cast_bits_to_bundle_expr_3: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_3: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(_cast_bits_to_array_expr_flattened[1], 0, 0)
+        wire _cast_bits_to_enum_expr_3: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_3.tag, 0)):
+            connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_3, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_enum_expr_3
+        connect _cast_bits_to_bundle_expr_flattened_3.body, bits(_cast_bits_to_array_expr_flattened[1], 1, 1)
+        connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
+        connect _cast_bits_to_array_expr[1], _cast_bits_to_bundle_expr_3
+        connect io_zeros.array_opt_bool_flip, _cast_bits_to_array_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_zeros_out.array_opt_bool, and(__enum_structural_eq_7, __enum_structural_eq_8) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_19: UInt<1>
+        match io_zeros.array_opt_bool_flip[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_19, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_19, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_20: UInt<1>
+        match _cast_bits_to_array_expr[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_20, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_20, UInt<1>(1)
+        wire _bundle_structural_eq_11: UInt<1>
+        connect _bundle_structural_eq_11, and(eq(_cast_enum_to_bits_expr_19, _cast_enum_to_bits_expr_20), eq(io_zeros.array_opt_bool_flip[0].body, _cast_bits_to_array_expr[0].body))
+        wire _cast_enum_to_bits_expr_21: UInt<1>
+        match io_zeros.array_opt_bool_flip[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_21, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_21, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_22: UInt<1>
+        match _cast_bits_to_array_expr[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_22, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_22, UInt<1>(1)
+        wire _bundle_structural_eq_12: UInt<1>
+        connect _bundle_structural_eq_12, and(eq(_cast_enum_to_bits_expr_21, _cast_enum_to_bits_expr_22), eq(io_zeros.array_opt_bool_flip[1].body, _cast_bits_to_array_expr[1].body))
+        connect parent_zeros_out.array_opt_bool_flip, and(_bundle_structural_eq_11, _bundle_structural_eq_12) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_4: Ty3
+        wire _cast_bits_to_bundle_expr_flattened_4: Ty9
+        connect _cast_bits_to_bundle_expr_flattened_4.`0`, bits(UInt<3>(0h0), 1, 0)
+        wire _cast_bits_to_bundle_expr_5: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_5: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_5.tag, bits(_cast_bits_to_bundle_expr_flattened_4.`0`, 0, 0)
+        wire _cast_bits_to_enum_expr_4: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_5.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_5.tag, _cast_bits_to_enum_expr_4
+        connect _cast_bits_to_bundle_expr_flattened_5.body, bits(_cast_bits_to_bundle_expr_flattened_4.`0`, 1, 1)
+        connect _cast_bits_to_bundle_expr_5.body, _cast_bits_to_bundle_expr_flattened_5.body
+        connect _cast_bits_to_bundle_expr_4.`0`, _cast_bits_to_bundle_expr_5
+        connect _cast_bits_to_bundle_expr_flattened_4.`1`, bits(UInt<3>(0h0), 2, 2)
+        connect _cast_bits_to_bundle_expr_4.`1`, _cast_bits_to_bundle_expr_flattened_4.`1`
+        connect io_zeros.struct_opt_bool_flip, _cast_bits_to_bundle_expr_4 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_zeros_out.struct_opt_bool, and(__enum_structural_eq_9, eq(io_zeros.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_4.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_23: UInt<1>
+        match io_zeros.struct_opt_bool_flip.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_23, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_23, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_24: UInt<1>
+        match _cast_bits_to_bundle_expr_4.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_24, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_24, UInt<1>(1)
+        wire _bundle_structural_eq_13: UInt<1>
+        connect _bundle_structural_eq_13, and(eq(_cast_enum_to_bits_expr_23, _cast_enum_to_bits_expr_24), eq(io_zeros.struct_opt_bool_flip.`0`.body, _cast_bits_to_bundle_expr_4.`0`.body))
+        connect parent_zeros_out.struct_opt_bool_flip, and(_bundle_structural_eq_13, eq(io_zeros.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_4.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect io_alternating.opt_unit_flip, _cast_bits_to_bundle_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_25: UInt<1>
+        match io_alternating.opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_25, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_25, UInt<1>(1)
+        wire _bundle_structural_eq_14: UInt<1>
+        connect _bundle_structural_eq_14, and(eq(_cast_enum_to_bits_expr_25, _cast_enum_to_bits_expr_14), eq(io_alternating.opt_unit.body, _cast_bits_to_bundle_expr.body))
+        connect parent_alternating_out.opt_unit, _bundle_structural_eq_14 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_26: UInt<1>
+        match io_alternating.opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_26, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_26, UInt<1>(1)
+        wire _bundle_structural_eq_15: UInt<1>
+        connect _bundle_structural_eq_15, and(eq(_cast_enum_to_bits_expr_26, _cast_enum_to_bits_expr_14), eq(io_alternating.opt_unit_flip.body, _cast_bits_to_bundle_expr.body))
+        connect parent_alternating_out.opt_unit_flip, _bundle_structural_eq_15 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_bundle_expr_6: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_6: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_6.tag, bits(UInt<2>(0h2), 0, 0)
+        wire _cast_bits_to_enum_expr_5: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_6.tag, 0)):
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_5, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_6.tag, _cast_bits_to_enum_expr_5
+        connect _cast_bits_to_bundle_expr_flattened_6.body, bits(UInt<2>(0h2), 1, 1)
+        connect _cast_bits_to_bundle_expr_6.body, _cast_bits_to_bundle_expr_flattened_6.body
+        connect io_alternating.opt_bool_flip, _cast_bits_to_bundle_expr_6 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool, __enum_structural_eq_10 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool_flip, __enum_structural_eq_11 @[module-XXXXXXXXXX.rs 14:1]
+        connect io_alternating.opt_opt_unit_flip, _cast_bits_to_bundle_expr_6 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit, __enum_structural_eq_12 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit_flip, __enum_structural_eq_13 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr_1: Ty2[2]
+        wire _cast_bits_to_array_expr_flattened_1: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened_1[0], bits(UInt<4>(0hA), 1, 0)
+        wire _cast_bits_to_bundle_expr_7: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_7: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_7.tag, bits(_cast_bits_to_array_expr_flattened_1[0], 0, 0)
+        wire _cast_bits_to_enum_expr_6: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_7.tag, 0)):
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_6, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_7.tag, _cast_bits_to_enum_expr_6
+        connect _cast_bits_to_bundle_expr_flattened_7.body, bits(_cast_bits_to_array_expr_flattened_1[0], 1, 1)
+        connect _cast_bits_to_bundle_expr_7.body, _cast_bits_to_bundle_expr_flattened_7.body
+        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_bundle_expr_7
+        connect _cast_bits_to_array_expr_flattened_1[1], bits(UInt<4>(0hA), 3, 2)
+        wire _cast_bits_to_bundle_expr_8: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_8: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_8.tag, bits(_cast_bits_to_array_expr_flattened_1[1], 0, 0)
+        wire _cast_bits_to_enum_expr_7: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_8.tag, 0)):
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_7, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_8.tag, _cast_bits_to_enum_expr_7
+        connect _cast_bits_to_bundle_expr_flattened_8.body, bits(_cast_bits_to_array_expr_flattened_1[1], 1, 1)
+        connect _cast_bits_to_bundle_expr_8.body, _cast_bits_to_bundle_expr_flattened_8.body
+        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_bundle_expr_8
+        connect io_alternating.array_opt_bool_flip, _cast_bits_to_array_expr_1 @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool, and(__enum_structural_eq_14, __enum_structural_eq_15) @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool_flip, and(__enum_structural_eq_16, __enum_structural_eq_17) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_9: Ty3
+        wire _cast_bits_to_bundle_expr_flattened_9: Ty9
+        connect _cast_bits_to_bundle_expr_flattened_9.`0`, bits(UInt<3>(0h2), 1, 0)
+        wire _cast_bits_to_bundle_expr_10: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_10: Ty8
+        connect _cast_bits_to_bundle_expr_flattened_10.tag, bits(_cast_bits_to_bundle_expr_flattened_9.`0`, 0, 0)
+        wire _cast_bits_to_enum_expr_8: Ty0
+        when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_10.tag, 0)):
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome|}(HdlNone)
+        else:
+            connect _cast_bits_to_enum_expr_8, {|HdlNone, HdlSome|}(HdlSome)
+        connect _cast_bits_to_bundle_expr_10.tag, _cast_bits_to_enum_expr_8
+        connect _cast_bits_to_bundle_expr_flattened_10.body, bits(_cast_bits_to_bundle_expr_flattened_9.`0`, 1, 1)
+        connect _cast_bits_to_bundle_expr_10.body, _cast_bits_to_bundle_expr_flattened_10.body
+        connect _cast_bits_to_bundle_expr_9.`0`, _cast_bits_to_bundle_expr_10
+        connect _cast_bits_to_bundle_expr_flattened_9.`1`, bits(UInt<3>(0h2), 2, 2)
+        connect _cast_bits_to_bundle_expr_9.`1`, _cast_bits_to_bundle_expr_flattened_9.`1`
+        connect io_alternating.struct_opt_bool_flip, _cast_bits_to_bundle_expr_9 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool, and(__enum_structural_eq_18, eq(io_alternating.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_9.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool_flip, and(__enum_structural_eq_19, eq(io_alternating.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_9.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child.io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_27: UInt<1>
+        match extern_child.io.opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_27, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_27, UInt<1>(1)
+        wire _bundle_structural_eq_16: UInt<1>
+        connect _bundle_structural_eq_16, and(eq(_cast_enum_to_bits_expr_27, _cast_enum_to_bits_expr_1), eq(extern_child.io.opt_unit.body, _bundle_literal_expr.body))
+        connect extern_child_out.opt_unit, _bundle_structural_eq_16 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_28: UInt<1>
+        match extern_child.io.opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_28, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_28, UInt<1>(1)
+        wire _bundle_structural_eq_17: UInt<1>
+        connect _bundle_structural_eq_17, and(eq(_cast_enum_to_bits_expr_28, _cast_enum_to_bits_expr_1), eq(extern_child.io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect extern_child_out.opt_unit_flip, _bundle_structural_eq_17 @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child.io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child_out.opt_bool, __enum_structural_eq_20 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_29: UInt<1>
+        match extern_child.io.opt_bool_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_29, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_29, UInt<1>(1)
+        wire _bundle_structural_eq_18: UInt<1>
+        connect _bundle_structural_eq_18, and(eq(_cast_enum_to_bits_expr_29, _cast_enum_to_bits_expr_4), eq(extern_child.io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect extern_child_out.opt_bool_flip, _bundle_structural_eq_18 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child.io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child_out.opt_opt_unit, __enum_structural_eq_21 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_30: UInt<1>
+        match extern_child.io.opt_opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_30, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_30, UInt<1>(1)
+        wire _bundle_structural_eq_19: UInt<1>
+        connect _bundle_structural_eq_19, and(eq(_cast_enum_to_bits_expr_30, _cast_enum_to_bits_expr_6), eq(extern_child.io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect extern_child_out.opt_opt_unit_flip, _bundle_structural_eq_19 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child_out.array_opt_bool, and(__enum_structural_eq_22, __enum_structural_eq_23) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_31: UInt<1>
+        match extern_child.io.array_opt_bool_flip[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_31, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_31, UInt<1>(1)
+        wire _bundle_structural_eq_20: UInt<1>
+        connect _bundle_structural_eq_20, and(eq(_cast_enum_to_bits_expr_31, _cast_enum_to_bits_expr_8), eq(extern_child.io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _cast_enum_to_bits_expr_32: UInt<1>
+        match extern_child.io.array_opt_bool_flip[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_32, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_32, UInt<1>(1)
+        wire _bundle_structural_eq_21: UInt<1>
+        connect _bundle_structural_eq_21, and(eq(_cast_enum_to_bits_expr_32, _cast_enum_to_bits_expr_10), eq(extern_child.io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect extern_child_out.array_opt_bool_flip, and(_bundle_structural_eq_20, _bundle_structural_eq_21) @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child_out.struct_opt_bool, and(__enum_structural_eq_24, eq(extern_child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_33: UInt<1>
+        match extern_child.io.struct_opt_bool_flip.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_33, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_33, UInt<1>(1)
+        wire _bundle_structural_eq_22: UInt<1>
+        connect _bundle_structural_eq_22, and(eq(_cast_enum_to_bits_expr_33, _cast_enum_to_bits_expr_12), eq(extern_child.io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect extern_child_out.struct_opt_bool_flip, and(_bundle_structural_eq_22, eq(extern_child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect child.io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_34: UInt<1>
+        match child.io.opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_34, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_34, UInt<1>(1)
+        wire _bundle_structural_eq_23: UInt<1>
+        connect _bundle_structural_eq_23, and(eq(_cast_enum_to_bits_expr_34, _cast_enum_to_bits_expr_1), eq(child.io.opt_unit.body, _bundle_literal_expr.body))
+        connect child_out.opt_unit, _bundle_structural_eq_23 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_enum_to_bits_expr_35: UInt<1>
+        match child.io.opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_35, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_35, UInt<1>(1)
+        wire _bundle_structural_eq_24: UInt<1>
+        connect _bundle_structural_eq_24, and(eq(_cast_enum_to_bits_expr_35, _cast_enum_to_bits_expr_1), eq(child.io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect child_out.opt_unit_flip, _bundle_structural_eq_24 @[module-XXXXXXXXXX.rs 13:1]
+        connect child.io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_36: UInt<1>
+        match child.io.opt_bool.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_36, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_36, UInt<1>(1)
+        wire _bundle_structural_eq_25: UInt<1>
+        connect _bundle_structural_eq_25, and(eq(_cast_enum_to_bits_expr_36, _cast_enum_to_bits_expr_4), eq(child.io.opt_bool.body, _bundle_literal_expr_2.body))
+        connect child_out.opt_bool, _bundle_structural_eq_25 @[module-XXXXXXXXXX.rs 14:1]
+        wire _cast_enum_to_bits_expr_37: UInt<1>
+        match child.io.opt_bool_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_37, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_37, UInt<1>(1)
+        wire _bundle_structural_eq_26: UInt<1>
+        connect _bundle_structural_eq_26, and(eq(_cast_enum_to_bits_expr_37, _cast_enum_to_bits_expr_4), eq(child.io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect child_out.opt_bool_flip, _bundle_structural_eq_26 @[module-XXXXXXXXXX.rs 14:1]
+        connect child.io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_38: UInt<1>
+        match child.io.opt_opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_38, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_38, UInt<1>(1)
+        wire _bundle_structural_eq_27: UInt<1>
+        connect _bundle_structural_eq_27, and(eq(_cast_enum_to_bits_expr_38, _cast_enum_to_bits_expr_6), eq(child.io.opt_opt_unit.body, _bundle_literal_expr_3.body))
+        connect child_out.opt_opt_unit, _bundle_structural_eq_27 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_enum_to_bits_expr_39: UInt<1>
+        match child.io.opt_opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_39, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_39, UInt<1>(1)
+        wire _bundle_structural_eq_28: UInt<1>
+        connect _bundle_structural_eq_28, and(eq(_cast_enum_to_bits_expr_39, _cast_enum_to_bits_expr_6), eq(child.io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect child_out.opt_opt_unit_flip, _bundle_structural_eq_28 @[module-XXXXXXXXXX.rs 15:1]
+        connect child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_40: UInt<1>
+        match child.io.array_opt_bool[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_40, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_40, UInt<1>(1)
+        wire _bundle_structural_eq_29: UInt<1>
+        connect _bundle_structural_eq_29, and(eq(_cast_enum_to_bits_expr_40, _cast_enum_to_bits_expr_8), eq(child.io.array_opt_bool[0].body, _array_literal_expr[0].body))
+        wire _cast_enum_to_bits_expr_41: UInt<1>
+        match child.io.array_opt_bool[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_41, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_41, UInt<1>(1)
+        wire _bundle_structural_eq_30: UInt<1>
+        connect _bundle_structural_eq_30, and(eq(_cast_enum_to_bits_expr_41, _cast_enum_to_bits_expr_10), eq(child.io.array_opt_bool[1].body, _array_literal_expr[1].body))
+        connect child_out.array_opt_bool, and(_bundle_structural_eq_29, _bundle_structural_eq_30) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_enum_to_bits_expr_42: UInt<1>
+        match child.io.array_opt_bool_flip[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_42, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_42, UInt<1>(1)
+        wire _bundle_structural_eq_31: UInt<1>
+        connect _bundle_structural_eq_31, and(eq(_cast_enum_to_bits_expr_42, _cast_enum_to_bits_expr_8), eq(child.io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _cast_enum_to_bits_expr_43: UInt<1>
+        match child.io.array_opt_bool_flip[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_43, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_43, UInt<1>(1)
+        wire _bundle_structural_eq_32: UInt<1>
+        connect _bundle_structural_eq_32, and(eq(_cast_enum_to_bits_expr_43, _cast_enum_to_bits_expr_10), eq(child.io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect child_out.array_opt_bool_flip, and(_bundle_structural_eq_31, _bundle_structural_eq_32) @[module-XXXXXXXXXX.rs 16:1]
+        connect child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_44: UInt<1>
+        match child.io.struct_opt_bool.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_44, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_44, UInt<1>(1)
+        wire _bundle_structural_eq_33: UInt<1>
+        connect _bundle_structural_eq_33, and(eq(_cast_enum_to_bits_expr_44, _cast_enum_to_bits_expr_12), eq(child.io.struct_opt_bool.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect child_out.struct_opt_bool, and(_bundle_structural_eq_33, eq(child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_enum_to_bits_expr_45: UInt<1>
+        match child.io.struct_opt_bool_flip.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_45, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_45, UInt<1>(1)
+        wire _bundle_structural_eq_34: UInt<1>
+        connect _bundle_structural_eq_34, and(eq(_cast_enum_to_bits_expr_45, _cast_enum_to_bits_expr_12), eq(child.io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect child_out.struct_opt_bool_flip, and(_bundle_structural_eq_34, eq(child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_46: UInt<1>
+        match io.opt_bool.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_46, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_46, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_46, _cast_enum_to_bits_expr_4): @[module-XXXXXXXXXX.rs 1:1]
+            match io.opt_bool.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq, eq(bits(io.opt_bool.body, 0, 0), bits(_bundle_literal_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_1, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_47: UInt<1>
+        match io.opt_opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_47, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_47, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_47, _cast_enum_to_bits_expr_6): @[module-XXXXXXXXXX.rs 1:1]
+            match io.opt_opt_unit.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_1, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    wire __enum_structural_eq_25: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_1, __enum_structural_eq_25 @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_25, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                    wire _cast_bits_to_bundle_expr_11: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_11: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_11.tag, bits(bits(io.opt_opt_unit.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_9: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_11.tag, 0)):
+                        connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_9, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_11.tag, _cast_bits_to_enum_expr_9
+                    connect _cast_bits_to_bundle_expr_flattened_11.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_11.body, _cast_bits_to_bundle_expr_flattened_11.body
+                    wire _cast_bits_to_bundle_expr_12: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_12: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_12.tag, bits(bits(_bundle_literal_expr_3.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_10: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_12.tag, 0)):
+                        connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_10, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_12.tag, _cast_bits_to_enum_expr_10
+                    connect _cast_bits_to_bundle_expr_flattened_12.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_12.body, _cast_bits_to_bundle_expr_flattened_12.body
+                    wire _cast_enum_to_bits_expr_48: UInt<1>
+                    match _cast_bits_to_bundle_expr_11.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_48, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_48, UInt<1>(1)
+                    wire _cast_enum_to_bits_expr_49: UInt<1>
+                    match _cast_bits_to_bundle_expr_12.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_49, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_49, UInt<1>(1)
+                    when eq(_cast_enum_to_bits_expr_48, _cast_enum_to_bits_expr_49): @[module-XXXXXXXXXX.rs 1:1]
+                        match _cast_bits_to_bundle_expr_11.tag: @[module-XXXXXXXXXX.rs 1:1]
+                            HdlNone:
+                                connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                            HdlSome:
+                                wire _cast_bits_to_bundle_expr_13: Ty6
+                                invalidate _cast_bits_to_bundle_expr_13
+                                wire _cast_bits_to_bundle_expr_14: Ty6
+                                invalidate _cast_bits_to_bundle_expr_14
+                                connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_2, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_50: UInt<1>
+        match io.array_opt_bool[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_50, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_50, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_50, _cast_enum_to_bits_expr_8): @[module-XXXXXXXXXX.rs 1:1]
+            match io.array_opt_bool[0].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_2, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_2, eq(bits(io.array_opt_bool[0].body, 0, 0), bits(_array_literal_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_3, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_51: UInt<1>
+        match io.array_opt_bool[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_51, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_51, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_51, _cast_enum_to_bits_expr_10): @[module-XXXXXXXXXX.rs 1:1]
+            match io.array_opt_bool[1].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_3, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_3, eq(bits(io.array_opt_bool[1].body, 0, 0), bits(_array_literal_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_4, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_52: UInt<1>
+        match io.struct_opt_bool.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_52, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_52, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_52, _cast_enum_to_bits_expr_12): @[module-XXXXXXXXXX.rs 1:1]
+            match io.struct_opt_bool.`0`.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_4, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_4, eq(bits(io.struct_opt_bool.`0`.body, 0, 0), bits(_bundle_literal_expr_5.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_5, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_53: UInt<1>
+        match io_zeros.opt_bool.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_53, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_53, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_53, _cast_enum_to_bits_expr_17): @[module-XXXXXXXXXX.rs 1:1]
+            match io_zeros.opt_bool.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_5, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_5, eq(bits(io_zeros.opt_bool.body, 0, 0), bits(_cast_bits_to_bundle_expr_1.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_6, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_54: UInt<1>
+        match io_zeros.opt_opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_54, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_54, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_54, _cast_enum_to_bits_expr_17): @[module-XXXXXXXXXX.rs 1:1]
+            match io_zeros.opt_opt_unit.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_6, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    wire __enum_structural_eq_26: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_6, __enum_structural_eq_26 @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_26, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                    wire _cast_bits_to_bundle_expr_15: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_13: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_13.tag, bits(bits(io_zeros.opt_opt_unit.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_11: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_13.tag, 0)):
+                        connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_11, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_15.tag, _cast_bits_to_enum_expr_11
+                    connect _cast_bits_to_bundle_expr_flattened_13.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_15.body, _cast_bits_to_bundle_expr_flattened_13.body
+                    wire _cast_bits_to_bundle_expr_16: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_14: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_14.tag, bits(bits(_cast_bits_to_bundle_expr_1.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_12: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_14.tag, 0)):
+                        connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_12, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_16.tag, _cast_bits_to_enum_expr_12
+                    connect _cast_bits_to_bundle_expr_flattened_14.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_16.body, _cast_bits_to_bundle_expr_flattened_14.body
+                    wire _cast_enum_to_bits_expr_55: UInt<1>
+                    match _cast_bits_to_bundle_expr_15.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_55, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_55, UInt<1>(1)
+                    wire _cast_enum_to_bits_expr_56: UInt<1>
+                    match _cast_bits_to_bundle_expr_16.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_56, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_56, UInt<1>(1)
+                    when eq(_cast_enum_to_bits_expr_55, _cast_enum_to_bits_expr_56): @[module-XXXXXXXXXX.rs 1:1]
+                        match _cast_bits_to_bundle_expr_15.tag: @[module-XXXXXXXXXX.rs 1:1]
+                            HdlNone:
+                                connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                            HdlSome:
+                                wire _cast_bits_to_bundle_expr_17: Ty6
+                                invalidate _cast_bits_to_bundle_expr_17
+                                wire _cast_bits_to_bundle_expr_18: Ty6
+                                invalidate _cast_bits_to_bundle_expr_18
+                                connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_7, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_57: UInt<1>
+        match io_zeros.array_opt_bool[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_57, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_57, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_57, _cast_enum_to_bits_expr_20): @[module-XXXXXXXXXX.rs 1:1]
+            match io_zeros.array_opt_bool[0].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_7, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_7, eq(bits(io_zeros.array_opt_bool[0].body, 0, 0), bits(_cast_bits_to_array_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_8, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_58: UInt<1>
+        match io_zeros.array_opt_bool[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_58, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_58, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_58, _cast_enum_to_bits_expr_22): @[module-XXXXXXXXXX.rs 1:1]
+            match io_zeros.array_opt_bool[1].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_8, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_8, eq(bits(io_zeros.array_opt_bool[1].body, 0, 0), bits(_cast_bits_to_array_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_9, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_59: UInt<1>
+        match io_zeros.struct_opt_bool.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_59, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_59, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_59, _cast_enum_to_bits_expr_24): @[module-XXXXXXXXXX.rs 1:1]
+            match io_zeros.struct_opt_bool.`0`.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_9, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_9, eq(bits(io_zeros.struct_opt_bool.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_4.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_10, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_60: UInt<1>
+        match io_alternating.opt_bool.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_60, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_60, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_61: UInt<1>
+        match _cast_bits_to_bundle_expr_6.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_61, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_61, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_60, _cast_enum_to_bits_expr_61): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.opt_bool.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_10, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_10, eq(bits(io_alternating.opt_bool.body, 0, 0), bits(_cast_bits_to_bundle_expr_6.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_11, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_62: UInt<1>
+        match io_alternating.opt_bool_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_62, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_62, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_62, _cast_enum_to_bits_expr_61): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.opt_bool_flip.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_11, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_11, eq(bits(io_alternating.opt_bool_flip.body, 0, 0), bits(_cast_bits_to_bundle_expr_6.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_12, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_63: UInt<1>
+        match io_alternating.opt_opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_63, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_63, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_63, _cast_enum_to_bits_expr_61): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.opt_opt_unit.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_12, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    wire __enum_structural_eq_27: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_12, __enum_structural_eq_27 @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_27, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                    wire _cast_bits_to_bundle_expr_19: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_15: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_15.tag, bits(bits(io_alternating.opt_opt_unit.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_13: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_15.tag, 0)):
+                        connect _cast_bits_to_enum_expr_13, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_13, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_19.tag, _cast_bits_to_enum_expr_13
+                    connect _cast_bits_to_bundle_expr_flattened_15.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_19.body, _cast_bits_to_bundle_expr_flattened_15.body
+                    wire _cast_bits_to_bundle_expr_20: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_16: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_16.tag, bits(bits(_cast_bits_to_bundle_expr_6.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_14: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_16.tag, 0)):
+                        connect _cast_bits_to_enum_expr_14, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_14, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_20.tag, _cast_bits_to_enum_expr_14
+                    connect _cast_bits_to_bundle_expr_flattened_16.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_20.body, _cast_bits_to_bundle_expr_flattened_16.body
+                    wire _cast_enum_to_bits_expr_64: UInt<1>
+                    match _cast_bits_to_bundle_expr_19.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_64, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_64, UInt<1>(1)
+                    wire _cast_enum_to_bits_expr_65: UInt<1>
+                    match _cast_bits_to_bundle_expr_20.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_65, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_65, UInt<1>(1)
+                    when eq(_cast_enum_to_bits_expr_64, _cast_enum_to_bits_expr_65): @[module-XXXXXXXXXX.rs 1:1]
+                        match _cast_bits_to_bundle_expr_19.tag: @[module-XXXXXXXXXX.rs 1:1]
+                            HdlNone:
+                                connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                            HdlSome:
+                                wire _cast_bits_to_bundle_expr_21: Ty6
+                                invalidate _cast_bits_to_bundle_expr_21
+                                wire _cast_bits_to_bundle_expr_22: Ty6
+                                invalidate _cast_bits_to_bundle_expr_22
+                                connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_13, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_66: UInt<1>
+        match io_alternating.opt_opt_unit_flip.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_66, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_66, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_66, _cast_enum_to_bits_expr_61): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.opt_opt_unit_flip.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_13, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    wire __enum_structural_eq_28: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_13, __enum_structural_eq_28 @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_28, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                    wire _cast_bits_to_bundle_expr_23: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_17: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_17.tag, bits(bits(io_alternating.opt_opt_unit_flip.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_15: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_17.tag, 0)):
+                        connect _cast_bits_to_enum_expr_15, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_15, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_23.tag, _cast_bits_to_enum_expr_15
+                    connect _cast_bits_to_bundle_expr_flattened_17.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_23.body, _cast_bits_to_bundle_expr_flattened_17.body
+                    wire _cast_bits_to_bundle_expr_24: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_18: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_18.tag, bits(bits(_cast_bits_to_bundle_expr_6.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_16: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_18.tag, 0)):
+                        connect _cast_bits_to_enum_expr_16, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_16, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_24.tag, _cast_bits_to_enum_expr_16
+                    connect _cast_bits_to_bundle_expr_flattened_18.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_24.body, _cast_bits_to_bundle_expr_flattened_18.body
+                    wire _cast_enum_to_bits_expr_67: UInt<1>
+                    match _cast_bits_to_bundle_expr_23.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_67, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_67, UInt<1>(1)
+                    wire _cast_enum_to_bits_expr_68: UInt<1>
+                    match _cast_bits_to_bundle_expr_24.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_68, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_68, UInt<1>(1)
+                    when eq(_cast_enum_to_bits_expr_67, _cast_enum_to_bits_expr_68): @[module-XXXXXXXXXX.rs 1:1]
+                        match _cast_bits_to_bundle_expr_23.tag: @[module-XXXXXXXXXX.rs 1:1]
+                            HdlNone:
+                                connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                            HdlSome:
+                                wire _cast_bits_to_bundle_expr_25: Ty6
+                                invalidate _cast_bits_to_bundle_expr_25
+                                wire _cast_bits_to_bundle_expr_26: Ty6
+                                invalidate _cast_bits_to_bundle_expr_26
+                                connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_14, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_69: UInt<1>
+        match io_alternating.array_opt_bool[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_69, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_69, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_70: UInt<1>
+        match _cast_bits_to_array_expr_1[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_70, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_70, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_69, _cast_enum_to_bits_expr_70): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.array_opt_bool[0].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_14, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_14, eq(bits(io_alternating.array_opt_bool[0].body, 0, 0), bits(_cast_bits_to_array_expr_1[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_15, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_71: UInt<1>
+        match io_alternating.array_opt_bool[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_71, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_71, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_72: UInt<1>
+        match _cast_bits_to_array_expr_1[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_72, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_72, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_71, _cast_enum_to_bits_expr_72): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.array_opt_bool[1].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_15, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_15, eq(bits(io_alternating.array_opt_bool[1].body, 0, 0), bits(_cast_bits_to_array_expr_1[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_16, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_73: UInt<1>
+        match io_alternating.array_opt_bool_flip[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_73, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_73, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_73, _cast_enum_to_bits_expr_70): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.array_opt_bool_flip[0].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_16, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_16, eq(bits(io_alternating.array_opt_bool_flip[0].body, 0, 0), bits(_cast_bits_to_array_expr_1[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_17, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_74: UInt<1>
+        match io_alternating.array_opt_bool_flip[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_74, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_74, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_74, _cast_enum_to_bits_expr_72): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.array_opt_bool_flip[1].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_17, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_17, eq(bits(io_alternating.array_opt_bool_flip[1].body, 0, 0), bits(_cast_bits_to_array_expr_1[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_18, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_75: UInt<1>
+        match io_alternating.struct_opt_bool.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_75, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_75, UInt<1>(1)
+        wire _cast_enum_to_bits_expr_76: UInt<1>
+        match _cast_bits_to_bundle_expr_9.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_76, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_76, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_75, _cast_enum_to_bits_expr_76): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.struct_opt_bool.`0`.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_18, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_18, eq(bits(io_alternating.struct_opt_bool.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_9.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_19, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_77: UInt<1>
+        match io_alternating.struct_opt_bool_flip.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_77, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_77, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_77, _cast_enum_to_bits_expr_76): @[module-XXXXXXXXXX.rs 1:1]
+            match io_alternating.struct_opt_bool_flip.`0`.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_19, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_19, eq(bits(io_alternating.struct_opt_bool_flip.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_9.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_20, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_78: UInt<1>
+        match extern_child.io.opt_bool.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_78, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_78, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_78, _cast_enum_to_bits_expr_4): @[module-XXXXXXXXXX.rs 1:1]
+            match extern_child.io.opt_bool.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_20, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_20, eq(bits(extern_child.io.opt_bool.body, 0, 0), bits(_bundle_literal_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_21, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_79: UInt<1>
+        match extern_child.io.opt_opt_unit.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_79, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_79, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_79, _cast_enum_to_bits_expr_6): @[module-XXXXXXXXXX.rs 1:1]
+            match extern_child.io.opt_opt_unit.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_21, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    wire __enum_structural_eq_29: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_21, __enum_structural_eq_29 @[module-XXXXXXXXXX.rs 1:1]
+                    connect __enum_structural_eq_29, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                    wire _cast_bits_to_bundle_expr_27: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_19: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_19.tag, bits(bits(extern_child.io.opt_opt_unit.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_17: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_19.tag, 0)):
+                        connect _cast_bits_to_enum_expr_17, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_17, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_27.tag, _cast_bits_to_enum_expr_17
+                    connect _cast_bits_to_bundle_expr_flattened_19.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_27.body, _cast_bits_to_bundle_expr_flattened_19.body
+                    wire _cast_bits_to_bundle_expr_28: Ty1
+                    wire _cast_bits_to_bundle_expr_flattened_20: Ty7
+                    connect _cast_bits_to_bundle_expr_flattened_20.tag, bits(bits(_bundle_literal_expr_3.body, 0, 0), 0, 0)
+                    wire _cast_bits_to_enum_expr_18: Ty0
+                    when eq(UInt<1>(0), tail(_cast_bits_to_bundle_expr_flattened_20.tag, 0)):
+                        connect _cast_bits_to_enum_expr_18, {|HdlNone, HdlSome|}(HdlNone)
+                    else:
+                        connect _cast_bits_to_enum_expr_18, {|HdlNone, HdlSome|}(HdlSome)
+                    connect _cast_bits_to_bundle_expr_28.tag, _cast_bits_to_enum_expr_18
+                    connect _cast_bits_to_bundle_expr_flattened_20.body, UInt<0>(0)
+                    connect _cast_bits_to_bundle_expr_28.body, _cast_bits_to_bundle_expr_flattened_20.body
+                    wire _cast_enum_to_bits_expr_80: UInt<1>
+                    match _cast_bits_to_bundle_expr_27.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_80, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_80, UInt<1>(1)
+                    wire _cast_enum_to_bits_expr_81: UInt<1>
+                    match _cast_bits_to_bundle_expr_28.tag:
+                        HdlNone:
+                            connect _cast_enum_to_bits_expr_81, UInt<1>(0)
+                        HdlSome:
+                            connect _cast_enum_to_bits_expr_81, UInt<1>(1)
+                    when eq(_cast_enum_to_bits_expr_80, _cast_enum_to_bits_expr_81): @[module-XXXXXXXXXX.rs 1:1]
+                        match _cast_bits_to_bundle_expr_27.tag: @[module-XXXXXXXXXX.rs 1:1]
+                            HdlNone:
+                                connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                            HdlSome:
+                                wire _cast_bits_to_bundle_expr_29: Ty6
+                                invalidate _cast_bits_to_bundle_expr_29
+                                wire _cast_bits_to_bundle_expr_30: Ty6
+                                invalidate _cast_bits_to_bundle_expr_30
+                                connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_22, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_82: UInt<1>
+        match extern_child.io.array_opt_bool[0].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_82, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_82, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_82, _cast_enum_to_bits_expr_8): @[module-XXXXXXXXXX.rs 1:1]
+            match extern_child.io.array_opt_bool[0].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_22, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_22, eq(bits(extern_child.io.array_opt_bool[0].body, 0, 0), bits(_array_literal_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_23, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_83: UInt<1>
+        match extern_child.io.array_opt_bool[1].tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_83, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_83, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_83, _cast_enum_to_bits_expr_10): @[module-XXXXXXXXXX.rs 1:1]
+            match extern_child.io.array_opt_bool[1].tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_23, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_23, eq(bits(extern_child.io.array_opt_bool[1].body, 0, 0), bits(_array_literal_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_24, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        wire _cast_enum_to_bits_expr_84: UInt<1>
+        match extern_child.io.struct_opt_bool.`0`.tag:
+            HdlNone:
+                connect _cast_enum_to_bits_expr_84, UInt<1>(0)
+            HdlSome:
+                connect _cast_enum_to_bits_expr_84, UInt<1>(1)
+        when eq(_cast_enum_to_bits_expr_84, _cast_enum_to_bits_expr_12): @[module-XXXXXXXXXX.rs 1:1]
+            match extern_child.io.struct_opt_bool.`0`.tag: @[module-XXXXXXXXXX.rs 1:1]
+                HdlNone:
+                    connect __enum_structural_eq_24, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                HdlSome:
+                    connect __enum_structural_eq_24, eq(bits(extern_child.io.struct_opt_bool.`0`.body, 0, 0), bits(_bundle_literal_expr_5.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+    extmodule check_deduce_structural_eq_flags_extern_child: @[module-XXXXXXXXXX-2.rs 1:1]
+        output io: Ty4 @[module-XXXXXXXXXX-2.rs 2:1]
+        defname = check_deduce_structural_eq_flags_extern_child
+    module check_deduce_structural_eq_flags_child: @[module-XXXXXXXXXX-3.rs 1:1]
+        output io: Ty4 @[module-XXXXXXXXXX-3.rs 2:1]
+        connect io.opt_unit, io.opt_unit_flip @[module-XXXXXXXXXX-3.rs 4:1]
+        connect io.opt_bool, io.opt_bool_flip @[module-XXXXXXXXXX-3.rs 5:1]
+        connect io.opt_opt_unit, io.opt_opt_unit_flip @[module-XXXXXXXXXX-3.rs 6:1]
+        connect io.array_opt_bool, io.array_opt_bool_flip @[module-XXXXXXXXXX-3.rs 7:1]
+        connect io.struct_opt_bool, io.struct_opt_bool_flip @[module-XXXXXXXXXX-3.rs 8:1]
+",
+    };
+    let m_bundle_of_uints = simplify_enums(m, SimplifyEnumsKind::ReplaceWithBundleOfUInts).unwrap();
+    dbg!(m_bundle_of_uints);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m_bundle_of_uints =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_structural_eq_flags_parent.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_structural_eq_flags_parent:
+    type Ty0 = {tag: UInt<1>, body: UInt<0>}
+    type Ty1 = {tag: UInt<1>, body: UInt<1>}
+    type Ty2 = {`0`: Ty1, `1`: UInt<1>}
+    type Ty3 = {flip opt_unit_flip: Ty0, opt_unit: Ty0, flip opt_bool_flip: Ty1, opt_bool: Ty1, flip opt_opt_unit_flip: Ty1, opt_opt_unit: Ty1, flip array_opt_bool_flip: Ty1[2], array_opt_bool: Ty1[2], flip struct_opt_bool_flip: Ty2, struct_opt_bool: Ty2}
+    type Ty4 = {opt_unit_flip: UInt<1>, opt_unit: UInt<1>, opt_bool_flip: UInt<1>, opt_bool: UInt<1>, opt_opt_unit_flip: UInt<1>, opt_opt_unit: UInt<1>, array_opt_bool_flip: UInt<1>, array_opt_bool: UInt<1>, struct_opt_bool_flip: UInt<1>, struct_opt_bool: UInt<1>}
+    type Ty5 = {}
+    type Ty6 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty7 = {io: Ty3}
+    module check_deduce_structural_eq_flags_parent: @[module-XXXXXXXXXX.rs 1:1]
+        input io: Ty3 @[module-XXXXXXXXXX.rs 2:1]
+        input io_zeros: Ty3 @[module-XXXXXXXXXX.rs 3:1]
+        input io_alternating: Ty3 @[module-XXXXXXXXXX.rs 4:1]
+        output parent_out: Ty4 @[module-XXXXXXXXXX.rs 5:1]
+        output parent_zeros_out: Ty4 @[module-XXXXXXXXXX.rs 6:1]
+        output parent_alternating_out: Ty4 @[module-XXXXXXXXXX.rs 7:1]
+        output extern_child_out: Ty4 @[module-XXXXXXXXXX.rs 8:1]
+        output child_out: Ty4 @[module-XXXXXXXXXX.rs 9:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_1: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_2: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_3: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_4: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_5: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_6: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_7: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_8: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_9: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_10: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_11: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_12: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_13: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_14: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_15: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_16: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_17: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_18: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_19: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_20: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_21: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_22: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_23: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_24: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        inst extern_child of check_deduce_structural_eq_flags_extern_child @[module-XXXXXXXXXX.rs 10:1]
+        inst child of check_deduce_structural_eq_flags_child @[module-XXXXXXXXXX.rs 11:1]
+        wire _bundle_literal_expr: Ty0
+        connect _bundle_literal_expr.tag, UInt<1>(0h1)
+        wire _bundle_literal_expr_1: Ty5
+        invalidate _bundle_literal_expr_1
+        connect _bundle_literal_expr.body, UInt<0>(0)
+        connect io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq: UInt<1>
+        connect _bundle_structural_eq, and(eq(io.opt_unit.tag, _bundle_literal_expr.tag), eq(io.opt_unit.body, _bundle_literal_expr.body))
+        connect parent_out.opt_unit, _bundle_structural_eq @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_1: UInt<1>
+        connect _bundle_structural_eq_1, and(eq(io.opt_unit_flip.tag, _bundle_literal_expr.tag), eq(io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect parent_out.opt_unit_flip, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_literal_expr_2: Ty1
+        connect _bundle_literal_expr_2.tag, UInt<1>(0h1)
+        connect _bundle_literal_expr_2.body, UInt<1>(0h1)
+        connect io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_out.opt_bool, __enum_structural_eq @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_structural_eq_2: UInt<1>
+        connect _bundle_structural_eq_2, and(eq(io.opt_bool_flip.tag, _bundle_literal_expr_2.tag), eq(io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect parent_out.opt_bool_flip, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_literal_expr_3: Ty1
+        connect _bundle_literal_expr_3.tag, UInt<1>(0h1)
+        wire _cast_bundle_to_bits_expr: Ty0
+        connect _cast_bundle_to_bits_expr.tag, _bundle_literal_expr.tag
+        connect _cast_bundle_to_bits_expr.body, _bundle_literal_expr.body
+        wire _cast_to_bits_expr: UInt<1>
+        connect _cast_to_bits_expr, cat(_cast_bundle_to_bits_expr.body, _cast_bundle_to_bits_expr.tag)
+        connect _bundle_literal_expr_3.body, _cast_to_bits_expr
+        connect io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_out.opt_opt_unit, __enum_structural_eq_1 @[module-XXXXXXXXXX.rs 15:1]
+        wire _bundle_structural_eq_3: UInt<1>
+        connect _bundle_structural_eq_3, and(eq(io.opt_opt_unit_flip.tag, _bundle_literal_expr_3.tag), eq(io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect parent_out.opt_opt_unit_flip, _bundle_structural_eq_3 @[module-XXXXXXXXXX.rs 15:1]
+        wire _array_literal_expr: Ty1[2]
+        wire _bundle_literal_expr_4: Ty1
+        connect _bundle_literal_expr_4.tag, UInt<1>(0h1)
+        connect _bundle_literal_expr_4.body, UInt<1>(0h0)
+        connect _array_literal_expr[0], _bundle_literal_expr_4
+        connect _array_literal_expr[1], _bundle_literal_expr_2
+        connect io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_out.array_opt_bool, and(__enum_structural_eq_2, __enum_structural_eq_3) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_structural_eq_4: UInt<1>
+        connect _bundle_structural_eq_4, and(eq(io.array_opt_bool_flip[0].tag, _array_literal_expr[0].tag), eq(io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _bundle_structural_eq_5: UInt<1>
+        connect _bundle_structural_eq_5, and(eq(io.array_opt_bool_flip[1].tag, _array_literal_expr[1].tag), eq(io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect parent_out.array_opt_bool_flip, and(_bundle_structural_eq_4, _bundle_structural_eq_5) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_literal_expr_5: Ty2
+        connect _bundle_literal_expr_5.`0`, _bundle_literal_expr_2
+        connect _bundle_literal_expr_5.`1`, UInt<1>(0h1)
+        connect io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_out.struct_opt_bool, and(__enum_structural_eq_4, eq(io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _bundle_structural_eq_6: UInt<1>
+        connect _bundle_structural_eq_6, and(eq(io.struct_opt_bool_flip.`0`.tag, _bundle_literal_expr_5.`0`.tag), eq(io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect parent_out.struct_opt_bool_flip, and(_bundle_structural_eq_6, eq(io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _cast_bits_to_bundle_expr: Ty0
+        wire _cast_bits_to_bundle_expr_flattened: Ty0
+        connect _cast_bits_to_bundle_expr_flattened.tag, bits(UInt<1>(0h0), 0, 0)
+        connect _cast_bits_to_bundle_expr.tag, _cast_bits_to_bundle_expr_flattened.tag
+        connect _cast_bits_to_bundle_expr_flattened.body, UInt<0>(0)
+        connect _cast_bits_to_bundle_expr.body, _cast_bits_to_bundle_expr_flattened.body
+        connect io_zeros.opt_unit_flip, _cast_bits_to_bundle_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_7: UInt<1>
+        connect _bundle_structural_eq_7, and(eq(io_zeros.opt_unit.tag, _cast_bits_to_bundle_expr.tag), eq(io_zeros.opt_unit.body, _cast_bits_to_bundle_expr.body))
+        connect parent_zeros_out.opt_unit, _bundle_structural_eq_7 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_8: UInt<1>
+        connect _bundle_structural_eq_8, and(eq(io_zeros.opt_unit_flip.tag, _cast_bits_to_bundle_expr.tag), eq(io_zeros.opt_unit_flip.body, _cast_bits_to_bundle_expr.body))
+        connect parent_zeros_out.opt_unit_flip, _bundle_structural_eq_8 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_bundle_expr_1: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_1: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_1.tag, bits(UInt<2>(0h0), 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(UInt<2>(0h0), 1, 1)
+        connect _cast_bits_to_bundle_expr_1.body, _cast_bits_to_bundle_expr_flattened_1.body
+        connect io_zeros.opt_bool_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_zeros_out.opt_bool, __enum_structural_eq_5 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_structural_eq_9: UInt<1>
+        connect _bundle_structural_eq_9, and(eq(io_zeros.opt_bool_flip.tag, _cast_bits_to_bundle_expr_1.tag), eq(io_zeros.opt_bool_flip.body, _cast_bits_to_bundle_expr_1.body))
+        connect parent_zeros_out.opt_bool_flip, _bundle_structural_eq_9 @[module-XXXXXXXXXX.rs 14:1]
+        connect io_zeros.opt_opt_unit_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_zeros_out.opt_opt_unit, __enum_structural_eq_6 @[module-XXXXXXXXXX.rs 15:1]
+        wire _bundle_structural_eq_10: UInt<1>
+        connect _bundle_structural_eq_10, and(eq(io_zeros.opt_opt_unit_flip.tag, _cast_bits_to_bundle_expr_1.tag), eq(io_zeros.opt_opt_unit_flip.body, _cast_bits_to_bundle_expr_1.body))
+        connect parent_zeros_out.opt_opt_unit_flip, _bundle_structural_eq_10 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr: Ty1[2]
+        wire _cast_bits_to_array_expr_flattened: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened[0], bits(UInt<4>(0h0), 1, 0)
+        wire _cast_bits_to_bundle_expr_2: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_2: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_2.tag, bits(_cast_bits_to_array_expr_flattened[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_flattened_2.body, bits(_cast_bits_to_array_expr_flattened[0], 1, 1)
+        connect _cast_bits_to_bundle_expr_2.body, _cast_bits_to_bundle_expr_flattened_2.body
+        connect _cast_bits_to_array_expr[0], _cast_bits_to_bundle_expr_2
+        connect _cast_bits_to_array_expr_flattened[1], bits(UInt<4>(0h0), 3, 2)
+        wire _cast_bits_to_bundle_expr_3: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_3: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_3.tag, bits(_cast_bits_to_array_expr_flattened[1], 0, 0)
+        connect _cast_bits_to_bundle_expr_3.tag, _cast_bits_to_bundle_expr_flattened_3.tag
+        connect _cast_bits_to_bundle_expr_flattened_3.body, bits(_cast_bits_to_array_expr_flattened[1], 1, 1)
+        connect _cast_bits_to_bundle_expr_3.body, _cast_bits_to_bundle_expr_flattened_3.body
+        connect _cast_bits_to_array_expr[1], _cast_bits_to_bundle_expr_3
+        connect io_zeros.array_opt_bool_flip, _cast_bits_to_array_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_zeros_out.array_opt_bool, and(__enum_structural_eq_7, __enum_structural_eq_8) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_structural_eq_11: UInt<1>
+        connect _bundle_structural_eq_11, and(eq(io_zeros.array_opt_bool_flip[0].tag, _cast_bits_to_array_expr[0].tag), eq(io_zeros.array_opt_bool_flip[0].body, _cast_bits_to_array_expr[0].body))
+        wire _bundle_structural_eq_12: UInt<1>
+        connect _bundle_structural_eq_12, and(eq(io_zeros.array_opt_bool_flip[1].tag, _cast_bits_to_array_expr[1].tag), eq(io_zeros.array_opt_bool_flip[1].body, _cast_bits_to_array_expr[1].body))
+        connect parent_zeros_out.array_opt_bool_flip, and(_bundle_structural_eq_11, _bundle_structural_eq_12) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_4: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_4: Ty6
+        connect _cast_bits_to_bundle_expr_flattened_4.`0`, bits(UInt<3>(0h0), 1, 0)
+        wire _cast_bits_to_bundle_expr_5: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_5: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_5.tag, bits(_cast_bits_to_bundle_expr_flattened_4.`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_flattened_5.body, bits(_cast_bits_to_bundle_expr_flattened_4.`0`, 1, 1)
+        connect _cast_bits_to_bundle_expr_5.body, _cast_bits_to_bundle_expr_flattened_5.body
+        connect _cast_bits_to_bundle_expr_4.`0`, _cast_bits_to_bundle_expr_5
+        connect _cast_bits_to_bundle_expr_flattened_4.`1`, bits(UInt<3>(0h0), 2, 2)
+        connect _cast_bits_to_bundle_expr_4.`1`, _cast_bits_to_bundle_expr_flattened_4.`1`
+        connect io_zeros.struct_opt_bool_flip, _cast_bits_to_bundle_expr_4 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_zeros_out.struct_opt_bool, and(__enum_structural_eq_9, eq(io_zeros.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_4.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _bundle_structural_eq_13: UInt<1>
+        connect _bundle_structural_eq_13, and(eq(io_zeros.struct_opt_bool_flip.`0`.tag, _cast_bits_to_bundle_expr_4.`0`.tag), eq(io_zeros.struct_opt_bool_flip.`0`.body, _cast_bits_to_bundle_expr_4.`0`.body))
+        connect parent_zeros_out.struct_opt_bool_flip, and(_bundle_structural_eq_13, eq(io_zeros.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_4.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect io_alternating.opt_unit_flip, _cast_bits_to_bundle_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_14: UInt<1>
+        connect _bundle_structural_eq_14, and(eq(io_alternating.opt_unit.tag, _cast_bits_to_bundle_expr.tag), eq(io_alternating.opt_unit.body, _cast_bits_to_bundle_expr.body))
+        connect parent_alternating_out.opt_unit, _bundle_structural_eq_14 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_15: UInt<1>
+        connect _bundle_structural_eq_15, and(eq(io_alternating.opt_unit_flip.tag, _cast_bits_to_bundle_expr.tag), eq(io_alternating.opt_unit_flip.body, _cast_bits_to_bundle_expr.body))
+        connect parent_alternating_out.opt_unit_flip, _bundle_structural_eq_15 @[module-XXXXXXXXXX.rs 13:1]
+        wire _cast_bits_to_bundle_expr_6: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_6: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_6.tag, bits(UInt<2>(0h2), 0, 0)
+        connect _cast_bits_to_bundle_expr_6.tag, _cast_bits_to_bundle_expr_flattened_6.tag
+        connect _cast_bits_to_bundle_expr_flattened_6.body, bits(UInt<2>(0h2), 1, 1)
+        connect _cast_bits_to_bundle_expr_6.body, _cast_bits_to_bundle_expr_flattened_6.body
+        connect io_alternating.opt_bool_flip, _cast_bits_to_bundle_expr_6 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool, __enum_structural_eq_10 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool_flip, __enum_structural_eq_11 @[module-XXXXXXXXXX.rs 14:1]
+        connect io_alternating.opt_opt_unit_flip, _cast_bits_to_bundle_expr_6 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit, __enum_structural_eq_12 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit_flip, __enum_structural_eq_13 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr_1: Ty1[2]
+        wire _cast_bits_to_array_expr_flattened_1: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened_1[0], bits(UInt<4>(0hA), 1, 0)
+        wire _cast_bits_to_bundle_expr_7: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_7: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_7.tag, bits(_cast_bits_to_array_expr_flattened_1[0], 0, 0)
+        connect _cast_bits_to_bundle_expr_7.tag, _cast_bits_to_bundle_expr_flattened_7.tag
+        connect _cast_bits_to_bundle_expr_flattened_7.body, bits(_cast_bits_to_array_expr_flattened_1[0], 1, 1)
+        connect _cast_bits_to_bundle_expr_7.body, _cast_bits_to_bundle_expr_flattened_7.body
+        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_bundle_expr_7
+        connect _cast_bits_to_array_expr_flattened_1[1], bits(UInt<4>(0hA), 3, 2)
+        wire _cast_bits_to_bundle_expr_8: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_8: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_8.tag, bits(_cast_bits_to_array_expr_flattened_1[1], 0, 0)
+        connect _cast_bits_to_bundle_expr_8.tag, _cast_bits_to_bundle_expr_flattened_8.tag
+        connect _cast_bits_to_bundle_expr_flattened_8.body, bits(_cast_bits_to_array_expr_flattened_1[1], 1, 1)
+        connect _cast_bits_to_bundle_expr_8.body, _cast_bits_to_bundle_expr_flattened_8.body
+        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_bundle_expr_8
+        connect io_alternating.array_opt_bool_flip, _cast_bits_to_array_expr_1 @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool, and(__enum_structural_eq_14, __enum_structural_eq_15) @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool_flip, and(__enum_structural_eq_16, __enum_structural_eq_17) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_9: Ty2
+        wire _cast_bits_to_bundle_expr_flattened_9: Ty6
+        connect _cast_bits_to_bundle_expr_flattened_9.`0`, bits(UInt<3>(0h2), 1, 0)
+        wire _cast_bits_to_bundle_expr_10: Ty1
+        wire _cast_bits_to_bundle_expr_flattened_10: Ty1
+        connect _cast_bits_to_bundle_expr_flattened_10.tag, bits(_cast_bits_to_bundle_expr_flattened_9.`0`, 0, 0)
+        connect _cast_bits_to_bundle_expr_10.tag, _cast_bits_to_bundle_expr_flattened_10.tag
+        connect _cast_bits_to_bundle_expr_flattened_10.body, bits(_cast_bits_to_bundle_expr_flattened_9.`0`, 1, 1)
+        connect _cast_bits_to_bundle_expr_10.body, _cast_bits_to_bundle_expr_flattened_10.body
+        connect _cast_bits_to_bundle_expr_9.`0`, _cast_bits_to_bundle_expr_10
+        connect _cast_bits_to_bundle_expr_flattened_9.`1`, bits(UInt<3>(0h2), 2, 2)
+        connect _cast_bits_to_bundle_expr_9.`1`, _cast_bits_to_bundle_expr_flattened_9.`1`
+        connect io_alternating.struct_opt_bool_flip, _cast_bits_to_bundle_expr_9 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool, and(__enum_structural_eq_18, eq(io_alternating.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_9.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool_flip, and(__enum_structural_eq_19, eq(io_alternating.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_9.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child.io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_16: UInt<1>
+        connect _bundle_structural_eq_16, and(eq(extern_child.io.opt_unit.tag, _bundle_literal_expr.tag), eq(extern_child.io.opt_unit.body, _bundle_literal_expr.body))
+        connect extern_child_out.opt_unit, _bundle_structural_eq_16 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_17: UInt<1>
+        connect _bundle_structural_eq_17, and(eq(extern_child.io.opt_unit_flip.tag, _bundle_literal_expr.tag), eq(extern_child.io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect extern_child_out.opt_unit_flip, _bundle_structural_eq_17 @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child.io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child_out.opt_bool, __enum_structural_eq_20 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_structural_eq_18: UInt<1>
+        connect _bundle_structural_eq_18, and(eq(extern_child.io.opt_bool_flip.tag, _bundle_literal_expr_2.tag), eq(extern_child.io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect extern_child_out.opt_bool_flip, _bundle_structural_eq_18 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child.io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child_out.opt_opt_unit, __enum_structural_eq_21 @[module-XXXXXXXXXX.rs 15:1]
+        wire _bundle_structural_eq_19: UInt<1>
+        connect _bundle_structural_eq_19, and(eq(extern_child.io.opt_opt_unit_flip.tag, _bundle_literal_expr_3.tag), eq(extern_child.io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect extern_child_out.opt_opt_unit_flip, _bundle_structural_eq_19 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child_out.array_opt_bool, and(__enum_structural_eq_22, __enum_structural_eq_23) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_structural_eq_20: UInt<1>
+        connect _bundle_structural_eq_20, and(eq(extern_child.io.array_opt_bool_flip[0].tag, _array_literal_expr[0].tag), eq(extern_child.io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _bundle_structural_eq_21: UInt<1>
+        connect _bundle_structural_eq_21, and(eq(extern_child.io.array_opt_bool_flip[1].tag, _array_literal_expr[1].tag), eq(extern_child.io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect extern_child_out.array_opt_bool_flip, and(_bundle_structural_eq_20, _bundle_structural_eq_21) @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child_out.struct_opt_bool, and(__enum_structural_eq_24, eq(extern_child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _bundle_structural_eq_22: UInt<1>
+        connect _bundle_structural_eq_22, and(eq(extern_child.io.struct_opt_bool_flip.`0`.tag, _bundle_literal_expr_5.`0`.tag), eq(extern_child.io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect extern_child_out.struct_opt_bool_flip, and(_bundle_structural_eq_22, eq(extern_child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect child.io.opt_unit_flip, _bundle_literal_expr @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_23: UInt<1>
+        connect _bundle_structural_eq_23, and(eq(child.io.opt_unit.tag, _bundle_literal_expr.tag), eq(child.io.opt_unit.body, _bundle_literal_expr.body))
+        connect child_out.opt_unit, _bundle_structural_eq_23 @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_structural_eq_24: UInt<1>
+        connect _bundle_structural_eq_24, and(eq(child.io.opt_unit_flip.tag, _bundle_literal_expr.tag), eq(child.io.opt_unit_flip.body, _bundle_literal_expr.body))
+        connect child_out.opt_unit_flip, _bundle_structural_eq_24 @[module-XXXXXXXXXX.rs 13:1]
+        connect child.io.opt_bool_flip, _bundle_literal_expr_2 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_structural_eq_25: UInt<1>
+        connect _bundle_structural_eq_25, and(eq(child.io.opt_bool.tag, _bundle_literal_expr_2.tag), eq(child.io.opt_bool.body, _bundle_literal_expr_2.body))
+        connect child_out.opt_bool, _bundle_structural_eq_25 @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_structural_eq_26: UInt<1>
+        connect _bundle_structural_eq_26, and(eq(child.io.opt_bool_flip.tag, _bundle_literal_expr_2.tag), eq(child.io.opt_bool_flip.body, _bundle_literal_expr_2.body))
+        connect child_out.opt_bool_flip, _bundle_structural_eq_26 @[module-XXXXXXXXXX.rs 14:1]
+        connect child.io.opt_opt_unit_flip, _bundle_literal_expr_3 @[module-XXXXXXXXXX.rs 15:1]
+        wire _bundle_structural_eq_27: UInt<1>
+        connect _bundle_structural_eq_27, and(eq(child.io.opt_opt_unit.tag, _bundle_literal_expr_3.tag), eq(child.io.opt_opt_unit.body, _bundle_literal_expr_3.body))
+        connect child_out.opt_opt_unit, _bundle_structural_eq_27 @[module-XXXXXXXXXX.rs 15:1]
+        wire _bundle_structural_eq_28: UInt<1>
+        connect _bundle_structural_eq_28, and(eq(child.io.opt_opt_unit_flip.tag, _bundle_literal_expr_3.tag), eq(child.io.opt_opt_unit_flip.body, _bundle_literal_expr_3.body))
+        connect child_out.opt_opt_unit_flip, _bundle_structural_eq_28 @[module-XXXXXXXXXX.rs 15:1]
+        connect child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_structural_eq_29: UInt<1>
+        connect _bundle_structural_eq_29, and(eq(child.io.array_opt_bool[0].tag, _array_literal_expr[0].tag), eq(child.io.array_opt_bool[0].body, _array_literal_expr[0].body))
+        wire _bundle_structural_eq_30: UInt<1>
+        connect _bundle_structural_eq_30, and(eq(child.io.array_opt_bool[1].tag, _array_literal_expr[1].tag), eq(child.io.array_opt_bool[1].body, _array_literal_expr[1].body))
+        connect child_out.array_opt_bool, and(_bundle_structural_eq_29, _bundle_structural_eq_30) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_structural_eq_31: UInt<1>
+        connect _bundle_structural_eq_31, and(eq(child.io.array_opt_bool_flip[0].tag, _array_literal_expr[0].tag), eq(child.io.array_opt_bool_flip[0].body, _array_literal_expr[0].body))
+        wire _bundle_structural_eq_32: UInt<1>
+        connect _bundle_structural_eq_32, and(eq(child.io.array_opt_bool_flip[1].tag, _array_literal_expr[1].tag), eq(child.io.array_opt_bool_flip[1].body, _array_literal_expr[1].body))
+        connect child_out.array_opt_bool_flip, and(_bundle_structural_eq_31, _bundle_structural_eq_32) @[module-XXXXXXXXXX.rs 16:1]
+        connect child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        wire _bundle_structural_eq_33: UInt<1>
+        connect _bundle_structural_eq_33, and(eq(child.io.struct_opt_bool.`0`.tag, _bundle_literal_expr_5.`0`.tag), eq(child.io.struct_opt_bool.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect child_out.struct_opt_bool, and(_bundle_structural_eq_33, eq(child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        wire _bundle_structural_eq_34: UInt<1>
+        connect _bundle_structural_eq_34, and(eq(child.io.struct_opt_bool_flip.`0`.tag, _bundle_literal_expr_5.`0`.tag), eq(child.io.struct_opt_bool_flip.`0`.body, _bundle_literal_expr_5.`0`.body))
+        connect child_out.struct_opt_bool_flip, and(_bundle_structural_eq_34, eq(child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io.opt_bool.tag, _bundle_literal_expr_2.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io.opt_bool.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq, eq(bits(io.opt_bool.body, 0, 0), bits(_bundle_literal_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_1, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io.opt_opt_unit.tag, _bundle_literal_expr_3.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io.opt_opt_unit.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_1, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_25: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_1, __enum_structural_eq_25 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_25, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                wire _cast_bits_to_bundle_expr_11: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_11: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_11.tag, bits(bits(io.opt_opt_unit.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_11.tag, _cast_bits_to_bundle_expr_flattened_11.tag
+                connect _cast_bits_to_bundle_expr_flattened_11.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_11.body, _cast_bits_to_bundle_expr_flattened_11.body
+                wire _cast_bits_to_bundle_expr_12: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_12: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_12.tag, bits(bits(_bundle_literal_expr_3.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_12.tag, _cast_bits_to_bundle_expr_flattened_12.tag
+                connect _cast_bits_to_bundle_expr_flattened_12.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_12.body, _cast_bits_to_bundle_expr_flattened_12.body
+                when eq(_cast_bits_to_bundle_expr_11.tag, _cast_bits_to_bundle_expr_12.tag): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(_cast_bits_to_bundle_expr_11.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_13: Ty5
+                        invalidate _cast_bits_to_bundle_expr_13
+                        wire _cast_bits_to_bundle_expr_14: Ty5
+                        invalidate _cast_bits_to_bundle_expr_14
+                        connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_2, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io.array_opt_bool[0].tag, _array_literal_expr[0].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io.array_opt_bool[0].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_2, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_2, eq(bits(io.array_opt_bool[0].body, 0, 0), bits(_array_literal_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_3, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io.array_opt_bool[1].tag, _array_literal_expr[1].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io.array_opt_bool[1].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_3, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_3, eq(bits(io.array_opt_bool[1].body, 0, 0), bits(_array_literal_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_4, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io.struct_opt_bool.`0`.tag, _bundle_literal_expr_5.`0`.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io.struct_opt_bool.`0`.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_4, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_4, eq(bits(io.struct_opt_bool.`0`.body, 0, 0), bits(_bundle_literal_expr_5.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_5, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_zeros.opt_bool.tag, _cast_bits_to_bundle_expr_1.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_zeros.opt_bool.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_5, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_5, eq(bits(io_zeros.opt_bool.body, 0, 0), bits(_cast_bits_to_bundle_expr_1.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_6, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_zeros.opt_opt_unit.tag, _cast_bits_to_bundle_expr_1.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_zeros.opt_opt_unit.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_6, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_26: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_6, __enum_structural_eq_26 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_26, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                wire _cast_bits_to_bundle_expr_15: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_13: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_13.tag, bits(bits(io_zeros.opt_opt_unit.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_15.tag, _cast_bits_to_bundle_expr_flattened_13.tag
+                connect _cast_bits_to_bundle_expr_flattened_13.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_15.body, _cast_bits_to_bundle_expr_flattened_13.body
+                wire _cast_bits_to_bundle_expr_16: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_14: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_14.tag, bits(bits(_cast_bits_to_bundle_expr_1.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_16.tag, _cast_bits_to_bundle_expr_flattened_14.tag
+                connect _cast_bits_to_bundle_expr_flattened_14.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_16.body, _cast_bits_to_bundle_expr_flattened_14.body
+                when eq(_cast_bits_to_bundle_expr_15.tag, _cast_bits_to_bundle_expr_16.tag): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(_cast_bits_to_bundle_expr_15.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_17: Ty5
+                        invalidate _cast_bits_to_bundle_expr_17
+                        wire _cast_bits_to_bundle_expr_18: Ty5
+                        invalidate _cast_bits_to_bundle_expr_18
+                        connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_7, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_zeros.array_opt_bool[0].tag, _cast_bits_to_array_expr[0].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_zeros.array_opt_bool[0].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_7, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_7, eq(bits(io_zeros.array_opt_bool[0].body, 0, 0), bits(_cast_bits_to_array_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_8, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_zeros.array_opt_bool[1].tag, _cast_bits_to_array_expr[1].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_zeros.array_opt_bool[1].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_8, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_8, eq(bits(io_zeros.array_opt_bool[1].body, 0, 0), bits(_cast_bits_to_array_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_9, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_zeros.struct_opt_bool.`0`.tag, _cast_bits_to_bundle_expr_4.`0`.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_zeros.struct_opt_bool.`0`.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_9, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_9, eq(bits(io_zeros.struct_opt_bool.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_4.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_10, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.opt_bool.tag, _cast_bits_to_bundle_expr_6.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.opt_bool.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_10, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_10, eq(bits(io_alternating.opt_bool.body, 0, 0), bits(_cast_bits_to_bundle_expr_6.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_11, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.opt_bool_flip.tag, _cast_bits_to_bundle_expr_6.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.opt_bool_flip.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_11, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_11, eq(bits(io_alternating.opt_bool_flip.body, 0, 0), bits(_cast_bits_to_bundle_expr_6.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_12, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.opt_opt_unit.tag, _cast_bits_to_bundle_expr_6.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.opt_opt_unit.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_12, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_27: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_12, __enum_structural_eq_27 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_27, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                wire _cast_bits_to_bundle_expr_19: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_15: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_15.tag, bits(bits(io_alternating.opt_opt_unit.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_19.tag, _cast_bits_to_bundle_expr_flattened_15.tag
+                connect _cast_bits_to_bundle_expr_flattened_15.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_19.body, _cast_bits_to_bundle_expr_flattened_15.body
+                wire _cast_bits_to_bundle_expr_20: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_16: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_16.tag, bits(bits(_cast_bits_to_bundle_expr_6.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_20.tag, _cast_bits_to_bundle_expr_flattened_16.tag
+                connect _cast_bits_to_bundle_expr_flattened_16.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_20.body, _cast_bits_to_bundle_expr_flattened_16.body
+                when eq(_cast_bits_to_bundle_expr_19.tag, _cast_bits_to_bundle_expr_20.tag): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(_cast_bits_to_bundle_expr_19.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_21: Ty5
+                        invalidate _cast_bits_to_bundle_expr_21
+                        wire _cast_bits_to_bundle_expr_22: Ty5
+                        invalidate _cast_bits_to_bundle_expr_22
+                        connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_13, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.opt_opt_unit_flip.tag, _cast_bits_to_bundle_expr_6.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.opt_opt_unit_flip.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_13, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_28: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_13, __enum_structural_eq_28 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_28, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                wire _cast_bits_to_bundle_expr_23: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_17: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_17.tag, bits(bits(io_alternating.opt_opt_unit_flip.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_23.tag, _cast_bits_to_bundle_expr_flattened_17.tag
+                connect _cast_bits_to_bundle_expr_flattened_17.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_23.body, _cast_bits_to_bundle_expr_flattened_17.body
+                wire _cast_bits_to_bundle_expr_24: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_18: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_18.tag, bits(bits(_cast_bits_to_bundle_expr_6.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_24.tag, _cast_bits_to_bundle_expr_flattened_18.tag
+                connect _cast_bits_to_bundle_expr_flattened_18.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_24.body, _cast_bits_to_bundle_expr_flattened_18.body
+                when eq(_cast_bits_to_bundle_expr_23.tag, _cast_bits_to_bundle_expr_24.tag): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(_cast_bits_to_bundle_expr_23.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_25: Ty5
+                        invalidate _cast_bits_to_bundle_expr_25
+                        wire _cast_bits_to_bundle_expr_26: Ty5
+                        invalidate _cast_bits_to_bundle_expr_26
+                        connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_14, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.array_opt_bool[0].tag, _cast_bits_to_array_expr_1[0].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.array_opt_bool[0].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_14, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_14, eq(bits(io_alternating.array_opt_bool[0].body, 0, 0), bits(_cast_bits_to_array_expr_1[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_15, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.array_opt_bool[1].tag, _cast_bits_to_array_expr_1[1].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.array_opt_bool[1].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_15, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_15, eq(bits(io_alternating.array_opt_bool[1].body, 0, 0), bits(_cast_bits_to_array_expr_1[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_16, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.array_opt_bool_flip[0].tag, _cast_bits_to_array_expr_1[0].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.array_opt_bool_flip[0].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_16, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_16, eq(bits(io_alternating.array_opt_bool_flip[0].body, 0, 0), bits(_cast_bits_to_array_expr_1[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_17, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.array_opt_bool_flip[1].tag, _cast_bits_to_array_expr_1[1].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.array_opt_bool_flip[1].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_17, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_17, eq(bits(io_alternating.array_opt_bool_flip[1].body, 0, 0), bits(_cast_bits_to_array_expr_1[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_18, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.struct_opt_bool.`0`.tag, _cast_bits_to_bundle_expr_9.`0`.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.struct_opt_bool.`0`.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_18, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_18, eq(bits(io_alternating.struct_opt_bool.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_9.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_19, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(io_alternating.struct_opt_bool_flip.`0`.tag, _cast_bits_to_bundle_expr_9.`0`.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(io_alternating.struct_opt_bool_flip.`0`.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_19, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_19, eq(bits(io_alternating.struct_opt_bool_flip.`0`.body, 0, 0), bits(_cast_bits_to_bundle_expr_9.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_20, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(extern_child.io.opt_bool.tag, _bundle_literal_expr_2.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(extern_child.io.opt_bool.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_20, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_20, eq(bits(extern_child.io.opt_bool.body, 0, 0), bits(_bundle_literal_expr_2.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_21, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(extern_child.io.opt_opt_unit.tag, _bundle_literal_expr_3.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(extern_child.io.opt_opt_unit.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_21, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_29: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_21, __enum_structural_eq_29 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_29, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                wire _cast_bits_to_bundle_expr_27: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_19: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_19.tag, bits(bits(extern_child.io.opt_opt_unit.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_27.tag, _cast_bits_to_bundle_expr_flattened_19.tag
+                connect _cast_bits_to_bundle_expr_flattened_19.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_27.body, _cast_bits_to_bundle_expr_flattened_19.body
+                wire _cast_bits_to_bundle_expr_28: Ty0
+                wire _cast_bits_to_bundle_expr_flattened_20: Ty0
+                connect _cast_bits_to_bundle_expr_flattened_20.tag, bits(bits(_bundle_literal_expr_3.body, 0, 0), 0, 0)
+                connect _cast_bits_to_bundle_expr_28.tag, _cast_bits_to_bundle_expr_flattened_20.tag
+                connect _cast_bits_to_bundle_expr_flattened_20.body, UInt<0>(0)
+                connect _cast_bits_to_bundle_expr_28.body, _cast_bits_to_bundle_expr_flattened_20.body
+                when eq(_cast_bits_to_bundle_expr_27.tag, _cast_bits_to_bundle_expr_28.tag): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(_cast_bits_to_bundle_expr_27.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_29: Ty5
+                        invalidate _cast_bits_to_bundle_expr_29
+                        wire _cast_bits_to_bundle_expr_30: Ty5
+                        invalidate _cast_bits_to_bundle_expr_30
+                        connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_22, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(extern_child.io.array_opt_bool[0].tag, _array_literal_expr[0].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(extern_child.io.array_opt_bool[0].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_22, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_22, eq(bits(extern_child.io.array_opt_bool[0].body, 0, 0), bits(_array_literal_expr[0].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_23, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(extern_child.io.array_opt_bool[1].tag, _array_literal_expr[1].tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(extern_child.io.array_opt_bool[1].tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_23, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_23, eq(bits(extern_child.io.array_opt_bool[1].body, 0, 0), bits(_array_literal_expr[1].body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_24, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(extern_child.io.struct_opt_bool.`0`.tag, _bundle_literal_expr_5.`0`.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(extern_child.io.struct_opt_bool.`0`.tag, UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_24, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_24, eq(bits(extern_child.io.struct_opt_bool.`0`.body, 0, 0), bits(_bundle_literal_expr_5.`0`.body, 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+    extmodule check_deduce_structural_eq_flags_extern_child: @[module-XXXXXXXXXX-2.rs 1:1]
+        output io: Ty3 @[module-XXXXXXXXXX-2.rs 2:1]
+        defname = check_deduce_structural_eq_flags_extern_child
+    module check_deduce_structural_eq_flags_child: @[module-XXXXXXXXXX-3.rs 1:1]
+        output io: Ty3 @[module-XXXXXXXXXX-3.rs 2:1]
+        connect io.opt_unit, io.opt_unit_flip @[module-XXXXXXXXXX-3.rs 4:1]
+        connect io.opt_bool, io.opt_bool_flip @[module-XXXXXXXXXX-3.rs 5:1]
+        connect io.opt_opt_unit, io.opt_opt_unit_flip @[module-XXXXXXXXXX-3.rs 6:1]
+        connect io.array_opt_bool, io.array_opt_bool_flip @[module-XXXXXXXXXX-3.rs 7:1]
+        connect io.struct_opt_bool, io.struct_opt_bool_flip @[module-XXXXXXXXXX-3.rs 8:1]
+",
+    };
+    let m_uints = simplify_enums(m, SimplifyEnumsKind::ReplaceWithUInt).unwrap();
+    dbg!(m_uints);
+    #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
+    assert_export_firrtl! {
+        m_uints =>
+        options: ExportOptions {
+            simplify_enums: None,
+            ..ExportOptions::default()
+        },
+        "/test/check_deduce_structural_eq_flags_parent.fir": r"FIRRTL version 3.2.0
+circuit check_deduce_structural_eq_flags_parent:
+    type Ty0 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty1 = {flip opt_unit_flip: UInt<1>, opt_unit: UInt<1>, flip opt_bool_flip: UInt<2>, opt_bool: UInt<2>, flip opt_opt_unit_flip: UInt<2>, opt_opt_unit: UInt<2>, flip array_opt_bool_flip: UInt<2>[2], array_opt_bool: UInt<2>[2], flip struct_opt_bool_flip: Ty0, struct_opt_bool: Ty0}
+    type Ty2 = {opt_unit_flip: UInt<1>, opt_unit: UInt<1>, opt_bool_flip: UInt<1>, opt_bool: UInt<1>, opt_opt_unit_flip: UInt<1>, opt_opt_unit: UInt<1>, array_opt_bool_flip: UInt<1>, array_opt_bool: UInt<1>, struct_opt_bool_flip: UInt<1>, struct_opt_bool: UInt<1>}
+    type Ty3 = {tag: UInt<1>, body: UInt<0>}
+    type Ty4 = {}
+    type Ty5 = {tag: UInt<1>, body: UInt<1>}
+    type Ty6 = {`0`: UInt<2>, `1`: UInt<1>}
+    type Ty7 = {io: Ty1}
+    module check_deduce_structural_eq_flags_parent: @[module-XXXXXXXXXX.rs 1:1]
+        input io: Ty1 @[module-XXXXXXXXXX.rs 2:1]
+        input io_zeros: Ty1 @[module-XXXXXXXXXX.rs 3:1]
+        input io_alternating: Ty1 @[module-XXXXXXXXXX.rs 4:1]
+        output parent_out: Ty2 @[module-XXXXXXXXXX.rs 5:1]
+        output parent_zeros_out: Ty2 @[module-XXXXXXXXXX.rs 6:1]
+        output parent_alternating_out: Ty2 @[module-XXXXXXXXXX.rs 7:1]
+        output extern_child_out: Ty2 @[module-XXXXXXXXXX.rs 8:1]
+        output child_out: Ty2 @[module-XXXXXXXXXX.rs 9:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_1: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_2: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_3: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_4: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_5: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_6: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_7: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_8: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_9: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_10: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_11: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_12: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_13: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_14: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_15: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_16: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_17: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_18: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_19: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_20: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_21: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_22: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_23: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        wire __enum_structural_eq_24: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        inst extern_child of check_deduce_structural_eq_flags_extern_child @[module-XXXXXXXXXX.rs 10:1]
+        inst child of check_deduce_structural_eq_flags_child @[module-XXXXXXXXXX.rs 11:1]
+        wire _bundle_literal_expr: Ty3
+        connect _bundle_literal_expr.tag, UInt<1>(0h1)
+        wire _bundle_literal_expr_1: Ty4
+        invalidate _bundle_literal_expr_1
+        connect _bundle_literal_expr.body, UInt<0>(0)
+        wire _cast_bundle_to_bits_expr: Ty3
+        connect _cast_bundle_to_bits_expr.tag, _bundle_literal_expr.tag
+        connect _cast_bundle_to_bits_expr.body, _bundle_literal_expr.body
+        wire _cast_to_bits_expr: UInt<1>
+        connect _cast_to_bits_expr, cat(_cast_bundle_to_bits_expr.body, _cast_bundle_to_bits_expr.tag)
+        connect io.opt_unit_flip, _cast_to_bits_expr @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_out.opt_unit, eq(io.opt_unit, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_out.opt_unit_flip, eq(io.opt_unit_flip, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        wire _bundle_literal_expr_2: Ty5
+        connect _bundle_literal_expr_2.tag, UInt<1>(0h1)
+        connect _bundle_literal_expr_2.body, UInt<1>(0h1)
+        wire _cast_bundle_to_bits_expr_1: Ty5
+        connect _cast_bundle_to_bits_expr_1.tag, _bundle_literal_expr_2.tag
+        connect _cast_bundle_to_bits_expr_1.body, _bundle_literal_expr_2.body
+        wire _cast_to_bits_expr_1: UInt<2>
+        connect _cast_to_bits_expr_1, cat(_cast_bundle_to_bits_expr_1.body, _cast_bundle_to_bits_expr_1.tag)
+        connect io.opt_bool_flip, _cast_to_bits_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_out.opt_bool, __enum_structural_eq @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_out.opt_bool_flip, eq(io.opt_bool_flip, _cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 14:1]
+        wire _bundle_literal_expr_3: Ty5
+        connect _bundle_literal_expr_3.tag, UInt<1>(0h1)
+        connect _bundle_literal_expr_3.body, _cast_to_bits_expr
+        wire _cast_bundle_to_bits_expr_2: Ty5
+        connect _cast_bundle_to_bits_expr_2.tag, _bundle_literal_expr_3.tag
+        connect _cast_bundle_to_bits_expr_2.body, _bundle_literal_expr_3.body
+        wire _cast_to_bits_expr_2: UInt<2>
+        connect _cast_to_bits_expr_2, cat(_cast_bundle_to_bits_expr_2.body, _cast_bundle_to_bits_expr_2.tag)
+        connect io.opt_opt_unit_flip, _cast_to_bits_expr_2 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_out.opt_opt_unit, __enum_structural_eq_1 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_out.opt_opt_unit_flip, eq(io.opt_opt_unit_flip, _cast_to_bits_expr_2) @[module-XXXXXXXXXX.rs 15:1]
+        wire _array_literal_expr: UInt<2>[2]
+        wire _bundle_literal_expr_4: Ty5
+        connect _bundle_literal_expr_4.tag, UInt<1>(0h1)
+        connect _bundle_literal_expr_4.body, UInt<1>(0h0)
+        wire _cast_bundle_to_bits_expr_3: Ty5
+        connect _cast_bundle_to_bits_expr_3.tag, _bundle_literal_expr_4.tag
+        connect _cast_bundle_to_bits_expr_3.body, _bundle_literal_expr_4.body
+        wire _cast_to_bits_expr_3: UInt<2>
+        connect _cast_to_bits_expr_3, cat(_cast_bundle_to_bits_expr_3.body, _cast_bundle_to_bits_expr_3.tag)
+        connect _array_literal_expr[0], _cast_to_bits_expr_3
+        connect _array_literal_expr[1], _cast_to_bits_expr_1
+        connect io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_out.array_opt_bool, and(__enum_structural_eq_2, __enum_structural_eq_3) @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_out.array_opt_bool_flip, and(eq(io.array_opt_bool_flip[0], _array_literal_expr[0]), eq(io.array_opt_bool_flip[1], _array_literal_expr[1])) @[module-XXXXXXXXXX.rs 16:1]
+        wire _bundle_literal_expr_5: Ty0
+        connect _bundle_literal_expr_5.`0`, _cast_to_bits_expr_1
+        connect _bundle_literal_expr_5.`1`, UInt<1>(0h1)
+        connect io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_out.struct_opt_bool, and(__enum_structural_eq_4, eq(io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_out.struct_opt_bool_flip, and(eq(io.struct_opt_bool_flip.`0`, _bundle_literal_expr_5.`0`), eq(io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect io_zeros.opt_unit_flip, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_zeros_out.opt_unit, eq(io_zeros.opt_unit, UInt<1>(0h0)) @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_zeros_out.opt_unit_flip, eq(io_zeros.opt_unit_flip, UInt<1>(0h0)) @[module-XXXXXXXXXX.rs 13:1]
+        connect io_zeros.opt_bool_flip, UInt<2>(0h0) @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_zeros_out.opt_bool, __enum_structural_eq_5 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_zeros_out.opt_bool_flip, eq(io_zeros.opt_bool_flip, UInt<2>(0h0)) @[module-XXXXXXXXXX.rs 14:1]
+        connect io_zeros.opt_opt_unit_flip, UInt<2>(0h0) @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_zeros_out.opt_opt_unit, __enum_structural_eq_6 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_zeros_out.opt_opt_unit_flip, eq(io_zeros.opt_opt_unit_flip, UInt<2>(0h0)) @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr: UInt<2>[2]
+        wire _cast_bits_to_array_expr_flattened: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened[0], bits(UInt<4>(0h0), 1, 0)
+        connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+        connect _cast_bits_to_array_expr_flattened[1], bits(UInt<4>(0h0), 3, 2)
+        connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+        connect io_zeros.array_opt_bool_flip, _cast_bits_to_array_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_zeros_out.array_opt_bool, and(__enum_structural_eq_7, __enum_structural_eq_8) @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_zeros_out.array_opt_bool_flip, and(eq(io_zeros.array_opt_bool_flip[0], _cast_bits_to_array_expr[0]), eq(io_zeros.array_opt_bool_flip[1], _cast_bits_to_array_expr[1])) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr: Ty0
+        wire _cast_bits_to_bundle_expr_flattened: Ty6
+        connect _cast_bits_to_bundle_expr_flattened.`0`, bits(UInt<3>(0h0), 1, 0)
+        connect _cast_bits_to_bundle_expr.`0`, _cast_bits_to_bundle_expr_flattened.`0`
+        connect _cast_bits_to_bundle_expr_flattened.`1`, bits(UInt<3>(0h0), 2, 2)
+        connect _cast_bits_to_bundle_expr.`1`, _cast_bits_to_bundle_expr_flattened.`1`
+        connect io_zeros.struct_opt_bool_flip, _cast_bits_to_bundle_expr @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_zeros_out.struct_opt_bool, and(__enum_structural_eq_9, eq(io_zeros.struct_opt_bool.`1`, _cast_bits_to_bundle_expr.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_zeros_out.struct_opt_bool_flip, and(eq(io_zeros.struct_opt_bool_flip.`0`, _cast_bits_to_bundle_expr.`0`), eq(io_zeros.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect io_alternating.opt_unit_flip, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_alternating_out.opt_unit, eq(io_alternating.opt_unit, UInt<1>(0h0)) @[module-XXXXXXXXXX.rs 13:1]
+        connect parent_alternating_out.opt_unit_flip, eq(io_alternating.opt_unit_flip, UInt<1>(0h0)) @[module-XXXXXXXXXX.rs 13:1]
+        connect io_alternating.opt_bool_flip, UInt<2>(0h2) @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool, __enum_structural_eq_10 @[module-XXXXXXXXXX.rs 14:1]
+        connect parent_alternating_out.opt_bool_flip, __enum_structural_eq_11 @[module-XXXXXXXXXX.rs 14:1]
+        connect io_alternating.opt_opt_unit_flip, UInt<2>(0h2) @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit, __enum_structural_eq_12 @[module-XXXXXXXXXX.rs 15:1]
+        connect parent_alternating_out.opt_opt_unit_flip, __enum_structural_eq_13 @[module-XXXXXXXXXX.rs 15:1]
+        wire _cast_bits_to_array_expr_1: UInt<2>[2]
+        wire _cast_bits_to_array_expr_flattened_1: UInt<2>[2]
+        connect _cast_bits_to_array_expr_flattened_1[0], bits(UInt<4>(0hA), 1, 0)
+        connect _cast_bits_to_array_expr_1[0], _cast_bits_to_array_expr_flattened_1[0]
+        connect _cast_bits_to_array_expr_flattened_1[1], bits(UInt<4>(0hA), 3, 2)
+        connect _cast_bits_to_array_expr_1[1], _cast_bits_to_array_expr_flattened_1[1]
+        connect io_alternating.array_opt_bool_flip, _cast_bits_to_array_expr_1 @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool, and(__enum_structural_eq_14, __enum_structural_eq_15) @[module-XXXXXXXXXX.rs 16:1]
+        connect parent_alternating_out.array_opt_bool_flip, and(__enum_structural_eq_16, __enum_structural_eq_17) @[module-XXXXXXXXXX.rs 16:1]
+        wire _cast_bits_to_bundle_expr_1: Ty0
+        wire _cast_bits_to_bundle_expr_flattened_1: Ty6
+        connect _cast_bits_to_bundle_expr_flattened_1.`0`, bits(UInt<3>(0h2), 1, 0)
+        connect _cast_bits_to_bundle_expr_1.`0`, _cast_bits_to_bundle_expr_flattened_1.`0`
+        connect _cast_bits_to_bundle_expr_flattened_1.`1`, bits(UInt<3>(0h2), 2, 2)
+        connect _cast_bits_to_bundle_expr_1.`1`, _cast_bits_to_bundle_expr_flattened_1.`1`
+        connect io_alternating.struct_opt_bool_flip, _cast_bits_to_bundle_expr_1 @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool, and(__enum_structural_eq_18, eq(io_alternating.struct_opt_bool.`1`, _cast_bits_to_bundle_expr_1.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect parent_alternating_out.struct_opt_bool_flip, and(__enum_structural_eq_19, eq(io_alternating.struct_opt_bool_flip.`1`, _cast_bits_to_bundle_expr_1.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child.io.opt_unit_flip, _cast_to_bits_expr @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child_out.opt_unit, eq(extern_child.io.opt_unit, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child_out.opt_unit_flip, eq(extern_child.io.opt_unit_flip, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        connect extern_child.io.opt_bool_flip, _cast_to_bits_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child_out.opt_bool, __enum_structural_eq_20 @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child_out.opt_bool_flip, eq(extern_child.io.opt_bool_flip, _cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 14:1]
+        connect extern_child.io.opt_opt_unit_flip, _cast_to_bits_expr_2 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child_out.opt_opt_unit, __enum_structural_eq_21 @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child_out.opt_opt_unit_flip, eq(extern_child.io.opt_opt_unit_flip, _cast_to_bits_expr_2) @[module-XXXXXXXXXX.rs 15:1]
+        connect extern_child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child_out.array_opt_bool, and(__enum_structural_eq_22, __enum_structural_eq_23) @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child_out.array_opt_bool_flip, and(eq(extern_child.io.array_opt_bool_flip[0], _array_literal_expr[0]), eq(extern_child.io.array_opt_bool_flip[1], _array_literal_expr[1])) @[module-XXXXXXXXXX.rs 16:1]
+        connect extern_child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child_out.struct_opt_bool, and(__enum_structural_eq_24, eq(extern_child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect extern_child_out.struct_opt_bool_flip, and(eq(extern_child.io.struct_opt_bool_flip.`0`, _bundle_literal_expr_5.`0`), eq(extern_child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect child.io.opt_unit_flip, _cast_to_bits_expr @[module-XXXXXXXXXX.rs 13:1]
+        connect child_out.opt_unit, eq(child.io.opt_unit, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        connect child_out.opt_unit_flip, eq(child.io.opt_unit_flip, _cast_to_bits_expr) @[module-XXXXXXXXXX.rs 13:1]
+        connect child.io.opt_bool_flip, _cast_to_bits_expr_1 @[module-XXXXXXXXXX.rs 14:1]
+        connect child_out.opt_bool, eq(child.io.opt_bool, _cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 14:1]
+        connect child_out.opt_bool_flip, eq(child.io.opt_bool_flip, _cast_to_bits_expr_1) @[module-XXXXXXXXXX.rs 14:1]
+        connect child.io.opt_opt_unit_flip, _cast_to_bits_expr_2 @[module-XXXXXXXXXX.rs 15:1]
+        connect child_out.opt_opt_unit, eq(child.io.opt_opt_unit, _cast_to_bits_expr_2) @[module-XXXXXXXXXX.rs 15:1]
+        connect child_out.opt_opt_unit_flip, eq(child.io.opt_opt_unit_flip, _cast_to_bits_expr_2) @[module-XXXXXXXXXX.rs 15:1]
+        connect child.io.array_opt_bool_flip, _array_literal_expr @[module-XXXXXXXXXX.rs 16:1]
+        connect child_out.array_opt_bool, and(eq(child.io.array_opt_bool[0], _array_literal_expr[0]), eq(child.io.array_opt_bool[1], _array_literal_expr[1])) @[module-XXXXXXXXXX.rs 16:1]
+        connect child_out.array_opt_bool_flip, and(eq(child.io.array_opt_bool_flip[0], _array_literal_expr[0]), eq(child.io.array_opt_bool_flip[1], _array_literal_expr[1])) @[module-XXXXXXXXXX.rs 16:1]
+        connect child.io.struct_opt_bool_flip, _bundle_literal_expr_5 @[module-XXXXXXXXXX.rs 17:1]
+        connect child_out.struct_opt_bool, and(eq(child.io.struct_opt_bool.`0`, _bundle_literal_expr_5.`0`), eq(child.io.struct_opt_bool.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect child_out.struct_opt_bool_flip, and(eq(child.io.struct_opt_bool_flip.`0`, _bundle_literal_expr_5.`0`), eq(child.io.struct_opt_bool_flip.`1`, _bundle_literal_expr_5.`1`)) @[module-XXXXXXXXXX.rs 17:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io.opt_bool, 0, 0), bits(_cast_to_bits_expr_1, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io.opt_bool, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq, eq(bits(bits(io.opt_bool, 1, 1), 0, 0), bits(bits(_cast_to_bits_expr_1, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_1, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io.opt_opt_unit, 0, 0), bits(_cast_to_bits_expr_2, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io.opt_opt_unit, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_1, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_25: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_1, __enum_structural_eq_25 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_25, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                when eq(bits(bits(bits(io.opt_opt_unit, 1, 1), 0, 0), 0, 0), bits(bits(bits(_cast_to_bits_expr_2, 1, 1), 0, 0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(bits(bits(bits(io.opt_opt_unit, 1, 1), 0, 0), 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_2: Ty4
+                        invalidate _cast_bits_to_bundle_expr_2
+                        wire _cast_bits_to_bundle_expr_3: Ty4
+                        invalidate _cast_bits_to_bundle_expr_3
+                        connect __enum_structural_eq_25, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_2, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io.array_opt_bool[0], 0, 0), bits(_array_literal_expr[0], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io.array_opt_bool[0], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_2, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_2, eq(bits(bits(io.array_opt_bool[0], 1, 1), 0, 0), bits(bits(_array_literal_expr[0], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_3, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io.array_opt_bool[1], 0, 0), bits(_array_literal_expr[1], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io.array_opt_bool[1], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_3, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_3, eq(bits(bits(io.array_opt_bool[1], 1, 1), 0, 0), bits(bits(_array_literal_expr[1], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_4, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io.struct_opt_bool.`0`, 0, 0), bits(_bundle_literal_expr_5.`0`, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io.struct_opt_bool.`0`, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_4, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_4, eq(bits(bits(io.struct_opt_bool.`0`, 1, 1), 0, 0), bits(bits(_bundle_literal_expr_5.`0`, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_5, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_zeros.opt_bool, 0, 0), bits(UInt<2>(0h0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_zeros.opt_bool, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_5, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_5, eq(bits(bits(io_zeros.opt_bool, 1, 1), 0, 0), bits(bits(UInt<2>(0h0), 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_6, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_zeros.opt_opt_unit, 0, 0), bits(UInt<2>(0h0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_zeros.opt_opt_unit, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_6, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_26: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_6, __enum_structural_eq_26 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_26, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                when eq(bits(bits(bits(io_zeros.opt_opt_unit, 1, 1), 0, 0), 0, 0), bits(bits(bits(UInt<2>(0h0), 1, 1), 0, 0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(bits(bits(bits(io_zeros.opt_opt_unit, 1, 1), 0, 0), 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_4: Ty4
+                        invalidate _cast_bits_to_bundle_expr_4
+                        wire _cast_bits_to_bundle_expr_5: Ty4
+                        invalidate _cast_bits_to_bundle_expr_5
+                        connect __enum_structural_eq_26, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_7, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_zeros.array_opt_bool[0], 0, 0), bits(_cast_bits_to_array_expr[0], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_zeros.array_opt_bool[0], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_7, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_7, eq(bits(bits(io_zeros.array_opt_bool[0], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr[0], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_8, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_zeros.array_opt_bool[1], 0, 0), bits(_cast_bits_to_array_expr[1], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_zeros.array_opt_bool[1], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_8, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_8, eq(bits(bits(io_zeros.array_opt_bool[1], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr[1], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_9, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_zeros.struct_opt_bool.`0`, 0, 0), bits(_cast_bits_to_bundle_expr.`0`, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_zeros.struct_opt_bool.`0`, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_9, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_9, eq(bits(bits(io_zeros.struct_opt_bool.`0`, 1, 1), 0, 0), bits(bits(_cast_bits_to_bundle_expr.`0`, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_10, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.opt_bool, 0, 0), bits(UInt<2>(0h2), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.opt_bool, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_10, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_10, eq(bits(bits(io_alternating.opt_bool, 1, 1), 0, 0), bits(bits(UInt<2>(0h2), 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_11, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.opt_bool_flip, 0, 0), bits(UInt<2>(0h2), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.opt_bool_flip, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_11, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_11, eq(bits(bits(io_alternating.opt_bool_flip, 1, 1), 0, 0), bits(bits(UInt<2>(0h2), 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_12, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.opt_opt_unit, 0, 0), bits(UInt<2>(0h2), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.opt_opt_unit, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_12, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_27: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_12, __enum_structural_eq_27 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_27, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                when eq(bits(bits(bits(io_alternating.opt_opt_unit, 1, 1), 0, 0), 0, 0), bits(bits(bits(UInt<2>(0h2), 1, 1), 0, 0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(bits(bits(bits(io_alternating.opt_opt_unit, 1, 1), 0, 0), 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_6: Ty4
+                        invalidate _cast_bits_to_bundle_expr_6
+                        wire _cast_bits_to_bundle_expr_7: Ty4
+                        invalidate _cast_bits_to_bundle_expr_7
+                        connect __enum_structural_eq_27, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_13, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.opt_opt_unit_flip, 0, 0), bits(UInt<2>(0h2), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.opt_opt_unit_flip, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_13, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_28: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_13, __enum_structural_eq_28 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_28, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                when eq(bits(bits(bits(io_alternating.opt_opt_unit_flip, 1, 1), 0, 0), 0, 0), bits(bits(bits(UInt<2>(0h2), 1, 1), 0, 0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(bits(bits(bits(io_alternating.opt_opt_unit_flip, 1, 1), 0, 0), 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_8: Ty4
+                        invalidate _cast_bits_to_bundle_expr_8
+                        wire _cast_bits_to_bundle_expr_9: Ty4
+                        invalidate _cast_bits_to_bundle_expr_9
+                        connect __enum_structural_eq_28, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_14, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.array_opt_bool[0], 0, 0), bits(_cast_bits_to_array_expr_1[0], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.array_opt_bool[0], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_14, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_14, eq(bits(bits(io_alternating.array_opt_bool[0], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr_1[0], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_15, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.array_opt_bool[1], 0, 0), bits(_cast_bits_to_array_expr_1[1], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.array_opt_bool[1], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_15, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_15, eq(bits(bits(io_alternating.array_opt_bool[1], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr_1[1], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_16, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.array_opt_bool_flip[0], 0, 0), bits(_cast_bits_to_array_expr_1[0], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.array_opt_bool_flip[0], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_16, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_16, eq(bits(bits(io_alternating.array_opt_bool_flip[0], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr_1[0], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_17, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.array_opt_bool_flip[1], 0, 0), bits(_cast_bits_to_array_expr_1[1], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.array_opt_bool_flip[1], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_17, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_17, eq(bits(bits(io_alternating.array_opt_bool_flip[1], 1, 1), 0, 0), bits(bits(_cast_bits_to_array_expr_1[1], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_18, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.struct_opt_bool.`0`, 0, 0), bits(_cast_bits_to_bundle_expr_1.`0`, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.struct_opt_bool.`0`, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_18, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_18, eq(bits(bits(io_alternating.struct_opt_bool.`0`, 1, 1), 0, 0), bits(bits(_cast_bits_to_bundle_expr_1.`0`, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_19, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(io_alternating.struct_opt_bool_flip.`0`, 0, 0), bits(_cast_bits_to_bundle_expr_1.`0`, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(io_alternating.struct_opt_bool_flip.`0`, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_19, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_19, eq(bits(bits(io_alternating.struct_opt_bool_flip.`0`, 1, 1), 0, 0), bits(bits(_cast_bits_to_bundle_expr_1.`0`, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_20, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(extern_child.io.opt_bool, 0, 0), bits(_cast_to_bits_expr_1, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(extern_child.io.opt_bool, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_20, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_20, eq(bits(bits(extern_child.io.opt_bool, 1, 1), 0, 0), bits(bits(_cast_to_bits_expr_1, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_21, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(extern_child.io.opt_opt_unit, 0, 0), bits(_cast_to_bits_expr_2, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(extern_child.io.opt_opt_unit, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_21, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire __enum_structural_eq_29: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_21, __enum_structural_eq_29 @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_29, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+                when eq(bits(bits(bits(extern_child.io.opt_opt_unit, 1, 1), 0, 0), 0, 0), bits(bits(bits(_cast_to_bits_expr_2, 1, 1), 0, 0), 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+                    when eq(bits(bits(bits(extern_child.io.opt_opt_unit, 1, 1), 0, 0), 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                        connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                    else:
+                        wire _cast_bits_to_bundle_expr_10: Ty4
+                        invalidate _cast_bits_to_bundle_expr_10
+                        wire _cast_bits_to_bundle_expr_11: Ty4
+                        invalidate _cast_bits_to_bundle_expr_11
+                        connect __enum_structural_eq_29, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_22, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(extern_child.io.array_opt_bool[0], 0, 0), bits(_array_literal_expr[0], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(extern_child.io.array_opt_bool[0], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_22, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_22, eq(bits(bits(extern_child.io.array_opt_bool[0], 1, 1), 0, 0), bits(bits(_array_literal_expr[0], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_23, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(extern_child.io.array_opt_bool[1], 0, 0), bits(_array_literal_expr[1], 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(extern_child.io.array_opt_bool[1], 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_23, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_23, eq(bits(bits(extern_child.io.array_opt_bool[1], 1, 1), 0, 0), bits(bits(_array_literal_expr[1], 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+        connect __enum_structural_eq_24, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(extern_child.io.struct_opt_bool.`0`, 0, 0), bits(_bundle_literal_expr_5.`0`, 0, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(extern_child.io.struct_opt_bool.`0`, 0, 0), UInt<1>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq_24, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                connect __enum_structural_eq_24, eq(bits(bits(extern_child.io.struct_opt_bool.`0`, 1, 1), 0, 0), bits(bits(_bundle_literal_expr_5.`0`, 1, 1), 0, 0)) @[module-XXXXXXXXXX.rs 1:1]
+    extmodule check_deduce_structural_eq_flags_extern_child: @[module-XXXXXXXXXX-2.rs 1:1]
+        output io: Ty1 @[module-XXXXXXXXXX-2.rs 2:1]
+        defname = check_deduce_structural_eq_flags_extern_child
+    module check_deduce_structural_eq_flags_child: @[module-XXXXXXXXXX-3.rs 1:1]
+        output io: Ty1 @[module-XXXXXXXXXX-3.rs 2:1]
+        connect io.opt_unit, io.opt_unit_flip @[module-XXXXXXXXXX-3.rs 4:1]
+        connect io.opt_bool, io.opt_bool_flip @[module-XXXXXXXXXX-3.rs 5:1]
+        connect io.opt_opt_unit, io.opt_opt_unit_flip @[module-XXXXXXXXXX-3.rs 6:1]
+        connect io.array_opt_bool, io.array_opt_bool_flip @[module-XXXXXXXXXX-3.rs 7:1]
+        connect io.struct_opt_bool, io.struct_opt_bool_flip @[module-XXXXXXXXXX-3.rs 8:1]
+",
+    };
+}
diff --git a/crates/fayalite/tests/module.rs b/crates/fayalite/tests/module.rs
index aa028f4..7d12810 100644
--- a/crates/fayalite/tests/module.rs
+++ b/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]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
-        match lhs: @[module-XXXXXXXXXX.rs 5:1]
+        wire _cast_enum_to_bits_expr: UInt<10>
+        match lhs:
             A:
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
-                    A:
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-                    B(_match_arm_value):
-                        skip
-                    C(_match_arm_value_1):
-                        skip
-            B(_match_arm_value_2):
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
-                    A:
-                        skip
-                    B(_match_arm_value_3):
-                        connect TestEnum_cmp_eq, eq(_match_arm_value_2, _match_arm_value_3) @[module-XXXXXXXXXX.rs 5:1]
-                    C(_match_arm_value_4):
-                        skip
-            C(_match_arm_value_5):
-                match rhs: @[module-XXXXXXXXXX.rs 5:1]
-                    A:
-                        skip
-                    B(_match_arm_value_6):
-                        skip
-                    C(_match_arm_value_7):
-                        wire _array_literal_expr: UInt<1>[3]
-                        connect _array_literal_expr[0], eq(_match_arm_value_5[0], _match_arm_value_7[0])
-                        connect _array_literal_expr[1], eq(_match_arm_value_5[1], _match_arm_value_7[1])
-                        connect _array_literal_expr[2], eq(_match_arm_value_5[2], _match_arm_value_7[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]
+                connect _cast_enum_to_bits_expr, UInt<10>(0)
+            B(_cast_enum_to_bits_expr_B):
+                connect _cast_enum_to_bits_expr, pad(cat(_cast_enum_to_bits_expr_B, UInt<2>(1)), 10)
+            C(_cast_enum_to_bits_expr_C):
+                wire _cast_array_to_bits_expr: UInt<1>[3]
+                connect _cast_array_to_bits_expr[0], _cast_enum_to_bits_expr_C[0]
+                connect _cast_array_to_bits_expr[1], _cast_enum_to_bits_expr_C[1]
+                connect _cast_array_to_bits_expr[2], _cast_enum_to_bits_expr_C[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 _cast_enum_to_bits_expr, pad(cat(_cast_to_bits_expr, UInt<2>(2)), 10)
+        wire _cast_enum_to_bits_expr_1: UInt<10>
+        match rhs:
+            A:
+                connect _cast_enum_to_bits_expr_1, UInt<10>(0)
+            B(_cast_enum_to_bits_expr_B_1):
+                connect _cast_enum_to_bits_expr_1, pad(cat(_cast_enum_to_bits_expr_B_1, UInt<2>(1)), 10)
+            C(_cast_enum_to_bits_expr_C_1):
+                wire _cast_array_to_bits_expr_1: UInt<1>[3]
+                connect _cast_array_to_bits_expr_1[0], _cast_enum_to_bits_expr_C_1[0]
+                connect _cast_array_to_bits_expr_1[1], _cast_enum_to_bits_expr_C_1[1]
+                connect _cast_array_to_bits_expr_1[2], _cast_enum_to_bits_expr_C_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 _cast_enum_to_bits_expr_1, pad(cat(_cast_to_bits_expr_1, UInt<2>(2)), 10)
+        connect eq, eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1) @[module-XXXXXXXXXX.rs 5:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -764,60 +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]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
-        match lhs.tag: @[module-XXXXXXXXXX.rs 5:1]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        connect eq, __enum_structural_eq @[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]
-                    A:
-                        connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-                    B:
-                        skip
-                    C:
-                        skip
+                connect _cast_enum_to_bits_expr, UInt<2>(0)
             B:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
-                    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
+                connect _cast_enum_to_bits_expr, UInt<2>(1)
             C:
-                match rhs.tag: @[module-XXXXXXXXXX.rs 5:1]
-                    A:
-                        skip
-                    B:
-                        skip
-                    C:
-                        wire _array_literal_expr: UInt<1>[3]
-                        wire _cast_bits_to_array_expr: UInt<1>[3]
-                        wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-                        connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-                        connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-                        connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-                        connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-                        connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-                        connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-                        wire _cast_bits_to_array_expr_1: UInt<1>[3]
-                        wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[0]
-                        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])
-                        connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
-                        connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[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]
+                connect _cast_enum_to_bits_expr, UInt<2>(2)
+        wire _cast_enum_to_bits_expr_1: UInt<2>
+        match rhs.tag:
+            A:
+                connect _cast_enum_to_bits_expr_1, UInt<2>(0)
+            B:
+                connect _cast_enum_to_bits_expr_1, UInt<2>(1)
+            C:
+                connect _cast_enum_to_bits_expr_1, UInt<2>(2)
+        when eq(_cast_enum_to_bits_expr, _cast_enum_to_bits_expr_1): @[module-XXXXXXXXXX.rs 1:1]
+            match lhs.tag: @[module-XXXXXXXXXX.rs 1:1]
+                A:
+                    connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+                B:
+                    connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
+                C:
+                    wire _cast_bits_to_array_expr: UInt<1>[3]
+                    wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                    connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+                    connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                    connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                    connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                    connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                    connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                    wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                    wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                    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]
+                    wire _array_structural_eq: UInt<1>
+                    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 _array_structural_eq_1: UInt<1>
+                    connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
+                    connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -834,51 +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]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
-        when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-                skip
-        else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-            when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-                skip
-            else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-                connect TestEnum_cmp_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
-        else when eq(rhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-            skip
-        else when eq(rhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-            skip
-        else:
-            wire _array_literal_expr: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
-            connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[0]
-            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])
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[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]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(lhs.tag, rhs.tag): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(lhs.tag, UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else when eq(lhs.tag, UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, eq(bits(lhs.body, 7, 0), bits(rhs.body, 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(lhs.body, 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                connect _cast_bits_to_array_expr_flattened[1], bits(bits(lhs.body, 2, 0), 1, 1)
+                connect _cast_bits_to_array_expr[1], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(lhs.body, 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[0]
+                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]
+                wire _array_structural_eq: UInt<1>
+                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 _array_structural_eq_1: UInt<1>
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
 ",
     };
     #[rustfmt::skip] // work around https://github.com/rust-lang/rustfmt/issues/6161
@@ -894,51 +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]
-        connect TestEnum_cmp_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 5:1]
-        when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-                connect TestEnum_cmp_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 5:1]
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-                skip
-        else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-            when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-                skip
-            else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-                connect TestEnum_cmp_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 5:1]
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 5:1]
-            skip
-        else when eq(bits(rhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 5:1]
-            skip
-        else:
-            wire _array_literal_expr: UInt<1>[3]
-            wire _cast_bits_to_array_expr: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
-            connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
-            connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
-            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], _cast_bits_to_array_expr_flattened[1]
-            connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
-            connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
-            wire _cast_bits_to_array_expr_1: UInt<1>[3]
-            wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[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_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])
-            connect _array_literal_expr[1], eq(_cast_bits_to_array_expr[1], _cast_bits_to_array_expr_1[1])
-            connect _array_literal_expr[2], eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[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]
+        wire __enum_structural_eq: UInt<1> @[module-XXXXXXXXXX.rs 1:1]
+        connect eq, __enum_structural_eq @[module-XXXXXXXXXX.rs 5:1]
+        connect __enum_structural_eq, UInt<1>(0h0) @[module-XXXXXXXXXX.rs 1:1]
+        when eq(bits(lhs, 1, 0), bits(rhs, 1, 0)): @[module-XXXXXXXXXX.rs 1:1]
+            when eq(bits(lhs, 1, 0), UInt<2>(0h0)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, UInt<1>(0h1) @[module-XXXXXXXXXX.rs 1:1]
+            else when eq(bits(lhs, 1, 0), UInt<2>(0h1)): @[module-XXXXXXXXXX.rs 1:1]
+                connect __enum_structural_eq, eq(bits(bits(lhs, 9, 2), 7, 0), bits(bits(rhs, 9, 2), 7, 0)) @[module-XXXXXXXXXX.rs 1:1]
+            else:
+                wire _cast_bits_to_array_expr: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened: UInt<1>[3]
+                connect _cast_bits_to_array_expr_flattened[0], bits(bits(bits(lhs, 9, 2), 2, 0), 0, 0)
+                connect _cast_bits_to_array_expr[0], _cast_bits_to_array_expr_flattened[0]
+                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], _cast_bits_to_array_expr_flattened[1]
+                connect _cast_bits_to_array_expr_flattened[2], bits(bits(bits(lhs, 9, 2), 2, 0), 2, 2)
+                connect _cast_bits_to_array_expr[2], _cast_bits_to_array_expr_flattened[2]
+                wire _cast_bits_to_array_expr_1: UInt<1>[3]
+                wire _cast_bits_to_array_expr_flattened_1: 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_1[0], _cast_bits_to_array_expr_flattened_1[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_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]
+                wire _array_structural_eq: UInt<1>
+                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 _array_structural_eq_1: UInt<1>
+                connect _array_structural_eq_1, and(_array_structural_eq, eq(_cast_bits_to_array_expr[2], _cast_bits_to_array_expr_1[2]))
+                connect __enum_structural_eq, _array_structural_eq_1 @[module-XXXXXXXXXX.rs 1:1]
 ",
     };
 }
@@ -4909,34 +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]
-        connect _array_literal_expr[0], eq(tuple_lhs.`0`, tuple_rhs.`0`)
-        connect _array_literal_expr[1], eq(tuple_lhs.`1`, tuple_rhs.`1`)
-        connect _array_literal_expr[2], eq(tuple_lhs.`2`, tuple_rhs.`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 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]
+        wire _bundle_structural_eq: UInt<1>
+        connect _bundle_structural_eq, and(eq(tuple_lhs.`0`, tuple_rhs.`0`), eq(tuple_lhs.`1`, tuple_rhs.`1`))
+        wire _bundle_structural_eq_1: UInt<1>
+        connect _bundle_structural_eq_1, and(_bundle_structural_eq, eq(tuple_lhs.`2`, tuple_rhs.`2`))
+        connect tuple_cmp_eq, _bundle_structural_eq_1 @[module-XXXXXXXXXX.rs 5:1]
+        connect tuple_cmp_ne, not(_bundle_structural_eq_1) @[module-XXXXXXXXXX.rs 7:1]
+        wire _bundle_structural_eq_2: UInt<1>
+        connect _bundle_structural_eq_2, and(eq(test_struct_lhs.a, test_struct_rhs.a), eq(test_struct_lhs.b, test_struct_rhs.b))
+        connect test_struct_cmp_eq, _bundle_structural_eq_2 @[module-XXXXXXXXXX.rs 11:1]
+        connect test_struct_cmp_ne, not(_bundle_structural_eq_2) @[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]
 ",
     };
 }
diff --git a/crates/fayalite/tests/sim.rs b/crates/fayalite/tests/sim.rs
index 223c4bc..343b87b 100644
--- a/crates/fayalite/tests/sim.rs
+++ b/crates/fayalite/tests/sim.rs
@@ -3749,3 +3749,67 @@ at module-XXXXXXXXXX.rs:12:1: in InstantiatedModule(formal_counter: formal_count
         }
     }
 }
+
+#[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!();
+    }
+}
diff --git a/crates/fayalite/tests/sim/expected/test_enum_structural_eq.txt b/crates/fayalite/tests/sim/expected/test_enum_structural_eq.txt
new file mode 100644
index 0000000..bad046e
--- /dev/null
+++ b/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: [],
+    ..
+}
\ No newline at end of file
diff --git a/crates/fayalite/tests/sim/expected/test_enum_structural_eq.vcd b/crates/fayalite/tests/sim/expected/test_enum_structural_eq.vcd
new file mode 100644
index 0000000..8da11c9
--- /dev/null
+++ b/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
diff --git a/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr b/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr
index 8eff725..75bb262 100644
--- a/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr
+++ b/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
diff --git a/crates/fayalite/visit_types.json b/crates/fayalite/visit_types.json
index 1267aa7..5c36374 100644
--- a/crates/fayalite/visit_types.json
+++ b/crates/fayalite/visit_types.json
@@ -1055,6 +1055,15 @@
                 "global()": "Visible"
             }
         },
+        "ops::StructuralEq": {
+            "data": {
+                "$kind": "Struct",
+                "$constructor": "ops::StructuralEq::with_flags",
+                "lhs()": "Visible",
+                "rhs()": "Visible",
+                "flags()": "Opaque"
+            }
+        },
         "BlockId": {
             "data": {
                 "$kind": "Opaque"