WIP: use HdlOption[the_type_var] or UInt[123 + n] for creating types

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

@@ -0,0 +1,708 @@
+use crate::{
+    hdl_type_common::{common_derives, get_target, TypeOptions, WrappedInConst},
+    kw, Errors, HdlAttr, PairsIterExt,
+};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote_spanned, ToTokens};
+use syn::{
+    parse_quote, parse_quote_spanned,
+    punctuated::{Pair, Punctuated},
+    spanned::Spanned,
+    token::Brace,
+    AngleBracketedGenericArguments, Attribute, Field, FieldMutability, Fields, FieldsNamed,
+    GenericParam, Generics, Ident, ItemStruct, Path, Token, Type, Visibility,
+};
+
+#[derive(Clone, Debug)]
+pub struct ParsedBundle {
+    pub(crate) attrs: Vec<Attribute>,
+    pub(crate) options: HdlAttr<TypeOptions>,
+    pub(crate) vis: Visibility,
+    pub(crate) struct_token: Token![struct],
+    pub(crate) ident: Ident,
+    pub(crate) generics: Generics,
+    pub(crate) fields: FieldsNamed,
+    pub(crate) field_flips: Vec<Option<HdlAttr<kw::flip>>>,
+    pub(crate) mask_type_ident: Ident,
+    pub(crate) mask_type_match_variant_ident: Ident,
+    pub(crate) match_variant_ident: Ident,
+    pub(crate) builder_ident: Ident,
+    pub(crate) mask_type_builder_ident: Ident,
+}
+
+impl ParsedBundle {
+    fn parse_field(
+        errors: &mut Errors,
+        field: &mut Field,
+        index: usize,
+    ) -> Option<HdlAttr<kw::flip>> {
+        let Field {
+            attrs,
+            vis: _,
+            mutability,
+            ident,
+            colon_token,
+            ty,
+        } = field;
+        let ident = ident.get_or_insert_with(|| format_ident!("_{}", index, span = ty.span()));
+        if !matches!(mutability, FieldMutability::None) {
+            // FIXME: use mutability as the spanned tokens,
+            // blocked on https://github.com/dtolnay/syn/issues/1717
+            errors.error(&ident, "field mutability is not supported");
+            *mutability = FieldMutability::None;
+        }
+        *mutability = FieldMutability::None;
+        colon_token.get_or_insert(Token![:](ident.span()));
+        let options = errors.unwrap_or_default(HdlAttr::parse_and_take_attr(attrs));
+        options
+    }
+    fn parse(item: ItemStruct) -> syn::Result<Self> {
+        let ItemStruct {
+            mut attrs,
+            vis,
+            struct_token,
+            ident,
+            generics,
+            fields,
+            semi_token,
+        } = item;
+        let mut errors = Errors::new();
+        let options = errors
+            .unwrap_or_default(HdlAttr::parse_and_take_attr(&mut attrs))
+            .unwrap_or_default();
+        let mut fields = match fields {
+            syn::Fields::Named(fields) => fields,
+            syn::Fields::Unnamed(fields) => {
+                errors.error(&fields, "#[hdl] struct must use curly braces: {}");
+                FieldsNamed {
+                    brace_token: Brace(fields.paren_token.span),
+                    named: fields.unnamed,
+                }
+            }
+            syn::Fields::Unit => {
+                errors.error(&fields, "#[hdl] struct must use curly braces: {}");
+                FieldsNamed {
+                    brace_token: Brace(semi_token.unwrap_or_default().span),
+                    named: Punctuated::default(),
+                }
+            }
+        };
+        let mut field_flips = Vec::with_capacity(fields.named.len());
+        for (index, field) in fields.named.iter_mut().enumerate() {
+            field_flips.push(Self::parse_field(&mut errors, field, index));
+        }
+        errors.finish()?;
+        Ok(Self {
+            attrs,
+            options,
+            vis,
+            struct_token,
+            generics,
+            fields,
+            field_flips,
+            mask_type_ident: format_ident!("__{}__MaskType", ident),
+            mask_type_match_variant_ident: format_ident!("__{}__MaskType__MatchVariant", ident),
+            match_variant_ident: format_ident!("__{}__MatchVariant", ident),
+            mask_type_builder_ident: format_ident!("__{}__MaskType__Builder", ident),
+            builder_ident: format_ident!("__{}__Builder", ident),
+            ident,
+        })
+    }
+}
+
+#[derive(Clone, Debug)]
+struct Builder {
+    vis: Visibility,
+    struct_token: Token![struct],
+    ident: Ident,
+    target: Path,
+    generics: Generics,
+    fields: FieldsNamed,
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+enum BuilderFieldState {
+    Unfilled,
+    Generic,
+    Filled,
+}
+
+impl Builder {
+    fn phantom_field_name(&self) -> Ident {
+        format_ident!("__phantom", span = self.ident.span())
+    }
+    fn phantom_field(&self) -> Field {
+        let target = &self.target;
+        let type_generics = self.generics.split_for_impl().1;
+        Field {
+            attrs: vec![],
+            vis: Visibility::Inherited,
+            mutability: FieldMutability::None,
+            ident: Some(self.phantom_field_name()),
+            colon_token: Some(Token![:](self.ident.span())),
+            ty: parse_quote_spanned! {self.ident.span()=>
+                ::fayalite::__std::marker::PhantomData<#target #type_generics>
+            },
+        }
+    }
+    fn builder_struct_generics(
+        &self,
+        mut get_field_state: impl FnMut(usize) -> BuilderFieldState,
+    ) -> Generics {
+        let mut retval = self.generics.clone();
+        for (field_index, field) in self.fields.named.iter().enumerate() {
+            match get_field_state(field_index) {
+                BuilderFieldState::Unfilled | BuilderFieldState::Filled => continue,
+                BuilderFieldState::Generic => {}
+            }
+            if !retval.params.empty_or_trailing() {
+                retval.params.push_punct(Token![,](self.ident.span()));
+            }
+            retval.params.push_value(GenericParam::Type(
+                type_var_for_field_name(field.ident.as_ref().unwrap()).into(),
+            ));
+        }
+        retval
+    }
+    fn builder_struct_ty(
+        &self,
+        mut get_field_state: impl FnMut(usize) -> BuilderFieldState,
+    ) -> Type {
+        let mut ty_arguments: AngleBracketedGenericArguments = if self.generics.params.is_empty() {
+            parse_quote_spanned! {self.ident.span()=>
+                <>
+            }
+        } else {
+            let builder_type_generics = self.generics.split_for_impl().1;
+            parse_quote! { #builder_type_generics }
+        };
+        for (field_index, Field { ident, ty, .. }) in self.fields.named.iter().enumerate() {
+            let ident = ident.as_ref().unwrap();
+            if !ty_arguments.args.empty_or_trailing() {
+                ty_arguments.args.push_punct(Token![,](self.ident.span()));
+            }
+            ty_arguments
+                .args
+                .push_value(match get_field_state(field_index) {
+                    BuilderFieldState::Unfilled => parse_quote_spanned! {self.ident.span()=>
+                        ::fayalite::bundle::Unfilled<#ty>
+                    },
+                    BuilderFieldState::Generic => {
+                        let type_var = type_var_for_field_name(ident);
+                        parse_quote_spanned! {self.ident.span()=>
+                            #type_var
+                        }
+                    }
+                    BuilderFieldState::Filled => parse_quote_spanned! {self.ident.span()=>
+                        ::fayalite::expr::Expr<#ty>
+                    },
+                });
+        }
+        let ident = &self.ident;
+        parse_quote_spanned! {ident.span()=>
+            #ident #ty_arguments
+        }
+    }
+}
+
+fn type_var_for_field_name(ident: &Ident) -> Ident {
+    format_ident!("__T_{}", ident)
+}
+
+fn field_fn_for_field_name(ident: &Ident) -> Ident {
+    format_ident!("field_{}", ident)
+}
+
+impl ToTokens for Builder {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            vis,
+            struct_token,
+            ident,
+            target,
+            generics,
+            fields,
+        } = self;
+        let phantom_field_name = self.phantom_field_name();
+        let builder_struct = ItemStruct {
+            attrs: vec![parse_quote_spanned! {ident.span()=>
+                #[allow(non_camel_case_types, dead_code)]
+            }],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: ident.clone(),
+            generics: self.builder_struct_generics(|_| BuilderFieldState::Generic),
+            fields: Fields::Named(FieldsNamed {
+                brace_token: fields.brace_token,
+                named: Punctuated::from_iter(
+                    [Pair::Punctuated(
+                        self.phantom_field(),
+                        Token![,](self.ident.span()),
+                    )]
+                    .into_iter()
+                    .chain(fields.named.pairs().map_pair_value_ref(|field| {
+                        let ident = field.ident.as_ref().unwrap();
+                        let type_var = type_var_for_field_name(ident);
+                        Field {
+                            vis: Visibility::Inherited,
+                            ty: parse_quote_spanned! {ident.span()=>
+                                #type_var
+                            },
+                            ..field.clone()
+                        }
+                    })),
+                ),
+            }),
+            semi_token: None,
+        };
+        builder_struct.to_tokens(tokens);
+        let field_idents = Vec::from_iter(
+            self.fields
+                .named
+                .iter()
+                .map(|field| field.ident.as_ref().unwrap()),
+        );
+        for (
+            field_index,
+            Field {
+                vis,
+                ident: field_ident,
+                ty,
+                ..
+            },
+        ) in self.fields.named.iter().enumerate()
+        {
+            let field_ident = field_ident.as_ref().unwrap();
+            let fn_ident = field_fn_for_field_name(field_ident);
+            let fn_generics = self.builder_struct_generics(|i| {
+                if i == field_index {
+                    BuilderFieldState::Unfilled
+                } else {
+                    BuilderFieldState::Generic
+                }
+            });
+            let (impl_generics, _, where_clause) = fn_generics.split_for_impl();
+            let unfilled_ty = self.builder_struct_ty(|i| {
+                if i == field_index {
+                    BuilderFieldState::Unfilled
+                } else {
+                    BuilderFieldState::Generic
+                }
+            });
+            let filled_ty = self.builder_struct_ty(|i| {
+                if i == field_index {
+                    BuilderFieldState::Filled
+                } else {
+                    BuilderFieldState::Generic
+                }
+            });
+            let pat_fields =
+                Vec::from_iter(self.fields.named.iter().enumerate().map(|(i, field)| {
+                    let field_ident = field.ident.as_ref().unwrap();
+                    if field_index == i {
+                        quote_spanned! {self.ident.span()=>
+                            #field_ident: _,
+                        }
+                    } else {
+                        quote_spanned! {self.ident.span()=>
+                            #field_ident,
+                        }
+                    }
+                }));
+            quote_spanned! {self.ident.span()=>
+                #[automatically_derived]
+                #[allow(non_camel_case_types, dead_code)]
+                impl #impl_generics #unfilled_ty
+                #where_clause
+                {
+                    #vis fn #fn_ident(
+                        self,
+                        #field_ident: ::fayalite::expr::Expr<#ty>,
+                    ) -> #filled_ty {
+                        let Self {
+                            #phantom_field_name: _,
+                            #(#pat_fields)*
+                        } = self;
+                        #ident {
+                            #phantom_field_name: ::fayalite::__std::marker::PhantomData,
+                            #(#field_idents,)*
+                        }
+                    }
+                }
+            }
+            .to_tokens(tokens);
+        }
+        let unfilled_generics = self.builder_struct_generics(|_| BuilderFieldState::Unfilled);
+        let unfilled_ty = self.builder_struct_ty(|_| BuilderFieldState::Unfilled);
+        let (unfilled_impl_generics, _, unfilled_where_clause) = unfilled_generics.split_for_impl();
+        quote_spanned! {self.ident.span()=>
+            #[automatically_derived]
+            #[allow(non_camel_case_types, dead_code)]
+            impl #unfilled_impl_generics ::fayalite::__std::default::Default for #unfilled_ty
+            #unfilled_where_clause
+            {
+                fn default() -> Self {
+                    #ident {
+                        #phantom_field_name: ::fayalite::__std::marker::PhantomData,
+                        #(#field_idents: ::fayalite::__std::default::Default::default(),)*
+                    }
+                }
+            }
+        }
+        .to_tokens(tokens);
+        let filled_generics = self.builder_struct_generics(|_| BuilderFieldState::Filled);
+        let filled_ty = self.builder_struct_ty(|_| BuilderFieldState::Filled);
+        let (filled_impl_generics, _, filled_where_clause) = filled_generics.split_for_impl();
+        let type_generics = self.generics.split_for_impl().1;
+        quote_spanned! {self.ident.span()=>
+            #[automatically_derived]
+            #[allow(non_camel_case_types, dead_code)]
+            impl #filled_impl_generics ::fayalite::expr::ToExpr for #filled_ty
+            #filled_where_clause
+            {
+                type Type = #target #type_generics;
+                fn to_expr(
+                    &self,
+                ) -> ::fayalite::expr::Expr<<Self as ::fayalite::expr::ToExpr>::Type> {
+                    let __ty = #target {
+                        #(#field_idents: ::fayalite::expr::Expr::ty(self.#field_idents),)*
+                    };
+                    let __field_values = [
+                        #(::fayalite::expr::Expr::canonical(self.#field_idents),)*
+                    ];
+                    ::fayalite::expr::ToExpr::to_expr(
+                        &::fayalite::expr::ops::BundleLiteral::new(__ty, &__field_values),
+                    )
+                }
+            }
+        }
+        .to_tokens(tokens);
+    }
+}
+
+impl ToTokens for ParsedBundle {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self {
+            attrs,
+            options,
+            vis,
+            struct_token,
+            ident,
+            generics,
+            fields,
+            field_flips,
+            mask_type_ident,
+            mask_type_match_variant_ident,
+            match_variant_ident,
+            builder_ident,
+            mask_type_builder_ident,
+        } = self;
+        let TypeOptions {
+            outline_generated: _,
+            connect_inexact,
+            target,
+        } = &options.body;
+        let target = get_target(target, ident);
+        let mut item_attrs = attrs.clone();
+        item_attrs.push(common_derives(ident.span()));
+        ItemStruct {
+            attrs: item_attrs,
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: ident.clone(),
+            generics: generics.clone(),
+            fields: Fields::Named(fields.clone()),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
+        let mut wrapped_in_const = WrappedInConst::new(tokens, ident.span());
+        let tokens = wrapped_in_const.inner();
+        let builder = Builder {
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: builder_ident.clone(),
+            target: target.clone(),
+            generics: generics.clone(),
+            fields: fields.clone(),
+        };
+        builder.to_tokens(tokens);
+        let unfilled_builder_ty = builder.builder_struct_ty(|_| BuilderFieldState::Unfilled);
+        let filled_builder_ty = builder.builder_struct_ty(|_| BuilderFieldState::Filled);
+        let mut mask_type_fields = fields.clone();
+        for Field { ident, ty, .. } in &mut mask_type_fields.named {
+            let ident = ident.as_ref().unwrap();
+            *ty = parse_quote_spanned! {ident.span()=>
+                <#ty as ::fayalite::ty::Type>::MaskType
+            };
+        }
+        let mask_type_builder = Builder {
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: mask_type_builder_ident.clone(),
+            target: mask_type_ident.clone().into(),
+            generics: generics.clone(),
+            fields: mask_type_fields.clone(),
+        };
+        mask_type_builder.to_tokens(tokens);
+        let unfilled_mask_type_builder_ty =
+            mask_type_builder.builder_struct_ty(|_| BuilderFieldState::Unfilled);
+        let filled_mask_type_builder_ty =
+            mask_type_builder.builder_struct_ty(|_| BuilderFieldState::Filled);
+        ItemStruct {
+            attrs: vec![
+                common_derives(ident.span()),
+                parse_quote_spanned! {ident.span()=>
+                    #[allow(non_camel_case_types, dead_code)]
+                },
+            ],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: mask_type_ident.clone(),
+            generics: generics.clone(),
+            fields: Fields::Named(mask_type_fields.clone()),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let mut mask_type_match_variant_fields = mask_type_fields;
+        for Field { ident, ty, .. } in &mut mask_type_match_variant_fields.named {
+            let ident = ident.as_ref().unwrap();
+            *ty = parse_quote_spanned! {ident.span()=>
+                ::fayalite::expr::Expr<#ty>
+            };
+        }
+        ItemStruct {
+            attrs: vec![
+                common_derives(ident.span()),
+                parse_quote_spanned! {ident.span()=>
+                    #[allow(non_camel_case_types, dead_code)]
+                },
+            ],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: mask_type_match_variant_ident.clone(),
+            generics: generics.clone(),
+            fields: Fields::Named(mask_type_match_variant_fields),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let mut match_variant_fields = fields.clone();
+        for Field { ident, ty, .. } in &mut match_variant_fields.named {
+            let ident = ident.as_ref().unwrap();
+            *ty = parse_quote_spanned! {ident.span()=>
+                ::fayalite::expr::Expr<#ty>
+            };
+        }
+        ItemStruct {
+            attrs: vec![
+                common_derives(ident.span()),
+                parse_quote_spanned! {ident.span()=>
+                    #[allow(non_camel_case_types, dead_code)]
+                },
+            ],
+            vis: vis.clone(),
+            struct_token: *struct_token,
+            ident: match_variant_ident.clone(),
+            generics: generics.clone(),
+            fields: Fields::Named(match_variant_fields),
+            semi_token: None,
+        }
+        .to_tokens(tokens);
+        let match_variant_body_fields =
+            Vec::from_iter(fields.named.iter().map(|Field { ident, .. }| {
+                let ident: &Ident = ident.as_ref().unwrap();
+                let ident_str = ident.to_string();
+                quote_spanned! {ident.span()=>
+                    #ident: ::fayalite::expr::Expr::field(__this, #ident_str),
+                }
+            }));
+        let mask_type_body_fields =
+            Vec::from_iter(fields.named.iter().map(|Field { ident, .. }| {
+                let ident: &Ident = ident.as_ref().unwrap();
+                quote_spanned! {ident.span()=>
+                    #ident: ::fayalite::ty::Type::mask_type(&self.#ident),
+                }
+            }));
+        let from_canonical_body_fields = Vec::from_iter(fields.named.iter().enumerate().zip(field_flips).map(
+            |((index, Field { ident, .. }), flip)| {
+                let ident: &Ident = ident.as_ref().unwrap();
+                let ident_str = ident.to_string();
+                let flipped = flip.is_some();
+                quote_spanned! {ident.span()=>
+                    #ident: {
+                        let ::fayalite::bundle::BundleField { name: __name, flipped: __flipped, ty: __ty } = __fields[#index];
+                        ::fayalite::__std::assert_eq!(&*__name, #ident_str);
+                        ::fayalite::__std::assert_eq!(__flipped, #flipped);
+                        ::fayalite::ty::Type::from_canonical(__ty)
+                    },
+                }
+            },
+        ));
+        let fields_body_fields = Vec::from_iter(fields.named.iter().zip(field_flips).map(
+            |(Field { ident, .. }, flip)| {
+                let ident: &Ident = ident.as_ref().unwrap();
+                let ident_str = ident.to_string();
+                let flipped = flip.is_some();
+                quote_spanned! {ident.span()=>
+                    ::fayalite::bundle::BundleField {
+                        name: ::fayalite::intern::Intern::intern(#ident_str),
+                        flipped: #flipped,
+                        ty: ::fayalite::ty::Type::canonical(&self.#ident),
+                    },
+                }
+            },
+        ));
+        let fields_len = fields.named.len();
+        quote_spanned! {ident.span()=>
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::ty::Type for #mask_type_ident #type_generics
+            #where_clause
+            {
+                type MaskType = #mask_type_ident #type_generics;
+                type MatchVariant = #mask_type_match_variant_ident #type_generics;
+                type MatchActiveScope = ();
+                type MatchVariantAndInactiveScope = ::fayalite::ty::MatchVariantWithoutScope<
+                    <Self as ::fayalite::ty::Type>::MatchVariant,
+                >;
+                type MatchVariantsIter = ::fayalite::__std::iter::Once<
+                    <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
+                >;
+                fn match_variants(
+                    __this: ::fayalite::expr::Expr<Self>,
+                    __module_builder: &mut ::fayalite::module::ModuleBuilder<
+                        ::fayalite::module::NormalModule,
+                    >,
+                    __source_location: ::fayalite::source_location::SourceLocation,
+                ) -> <Self as ::fayalite::ty::Type>::MatchVariantsIter {
+                    let __retval = #mask_type_match_variant_ident {
+                        #(#match_variant_body_fields)*
+                    };
+                    ::fayalite::__std::iter::once(::fayalite::ty::MatchVariantWithoutScope(__retval))
+                }
+                fn mask_type(&self) -> <Self as ::fayalite::ty::Type>::MaskType {
+                    *self
+                }
+                fn canonical(&self) -> ::fayalite::ty::CanonicalType {
+                    ::fayalite::ty::Type::canonical(&::fayalite::bundle::Bundle::new(::fayalite::bundle::BundleType::fields(self)))
+                }
+                #[track_caller]
+                fn from_canonical(__canonical_type: ::fayalite::ty::CanonicalType) -> Self {
+                    let ::fayalite::ty::CanonicalType::Bundle(__bundle) = __canonical_type else {
+                        ::fayalite::__std::panic!("expected bundle");
+                    };
+                    let __fields = ::fayalite::bundle::BundleType::fields(&__bundle);
+                    ::fayalite::__std::assert_eq!(__fields.len(), #fields_len, "bundle has wrong number of fields");
+                    Self {
+                        #(#from_canonical_body_fields)*
+                    }
+                }
+                fn source_location() -> ::fayalite::source_location::SourceLocation {
+                    ::fayalite::source_location::SourceLocation::caller()
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::bundle::BundleType for #mask_type_ident #type_generics
+            #where_clause
+            {
+                type Builder = #unfilled_mask_type_builder_ty;
+                type FilledBuilder = #filled_mask_type_builder_ty;
+                fn fields(&self) -> ::fayalite::intern::Interned<[::fayalite::bundle::BundleField]> {
+                    ::fayalite::intern::Intern::intern(&[#(#fields_body_fields)*][..])
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::ty::TypeWithDeref for #mask_type_ident #type_generics
+            #where_clause
+            {
+                fn expr_deref(__this: &::fayalite::expr::Expr<Self>) -> &<Self as ::fayalite::ty::Type>::MatchVariant {
+                    let __this = *__this;
+                    let __retval = #mask_type_match_variant_ident {
+                        #(#match_variant_body_fields)*
+                    };
+                    ::fayalite::intern::Interned::<_>::into_inner(::fayalite::intern::Intern::intern_sized(__retval))
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::ty::Type for #target #type_generics
+            #where_clause
+            {
+                type MaskType = #mask_type_ident #type_generics;
+                type MatchVariant = #match_variant_ident #type_generics;
+                type MatchActiveScope = ();
+                type MatchVariantAndInactiveScope = ::fayalite::ty::MatchVariantWithoutScope<
+                    <Self as ::fayalite::ty::Type>::MatchVariant,
+                >;
+                type MatchVariantsIter = ::fayalite::__std::iter::Once<
+                    <Self as ::fayalite::ty::Type>::MatchVariantAndInactiveScope,
+                >;
+                fn match_variants(
+                    __this: ::fayalite::expr::Expr<Self>,
+                    __module_builder: &mut ::fayalite::module::ModuleBuilder<
+                        ::fayalite::module::NormalModule,
+                    >,
+                    __source_location: ::fayalite::source_location::SourceLocation,
+                ) -> <Self as ::fayalite::ty::Type>::MatchVariantsIter {
+                    let __retval = #match_variant_ident {
+                        #(#match_variant_body_fields)*
+                    };
+                    ::fayalite::__std::iter::once(::fayalite::ty::MatchVariantWithoutScope(__retval))
+                }
+                fn mask_type(&self) -> <Self as ::fayalite::ty::Type>::MaskType {
+                    #mask_type_ident {
+                        #(#mask_type_body_fields)*
+                    }
+                }
+                fn canonical(&self) -> ::fayalite::ty::CanonicalType {
+                    ::fayalite::ty::Type::canonical(&::fayalite::bundle::Bundle::new(::fayalite::bundle::BundleType::fields(self)))
+                }
+                #[track_caller]
+                fn from_canonical(__canonical_type: ::fayalite::ty::CanonicalType) -> Self {
+                    let ::fayalite::ty::CanonicalType::Bundle(__bundle) = __canonical_type else {
+                        ::fayalite::__std::panic!("expected bundle");
+                    };
+                    let __fields = ::fayalite::bundle::BundleType::fields(&__bundle);
+                    ::fayalite::__std::assert_eq!(__fields.len(), #fields_len, "bundle has wrong number of fields");
+                    Self {
+                        #(#from_canonical_body_fields)*
+                    }
+                }
+                fn source_location() -> ::fayalite::source_location::SourceLocation {
+                    ::fayalite::source_location::SourceLocation::caller()
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::bundle::BundleType for #target #type_generics
+            #where_clause
+            {
+                type Builder = #unfilled_builder_ty;
+                type FilledBuilder = #filled_builder_ty;
+                fn fields(&self) -> ::fayalite::intern::Interned<[::fayalite::bundle::BundleField]> {
+                    ::fayalite::intern::Intern::intern(&[#(#fields_body_fields)*][..])
+                }
+            }
+            #[automatically_derived]
+            impl #impl_generics ::fayalite::ty::TypeWithDeref for #target #type_generics
+            #where_clause
+            {
+                fn expr_deref(__this: &::fayalite::expr::Expr<Self>) -> &<Self as ::fayalite::ty::Type>::MatchVariant {
+                    let __this = *__this;
+                    let __retval = #match_variant_ident {
+                        #(#match_variant_body_fields)*
+                    };
+                    ::fayalite::intern::Interned::<_>::into_inner(::fayalite::intern::Intern::intern_sized(__retval))
+                }
+            }
+        }
+        .to_tokens(tokens);
+    }
+}
+
+pub(crate) fn hdl_bundle(item: ItemStruct) -> syn::Result<TokenStream> {
+    let item = ParsedBundle::parse(item)?;
+    let outline_generated = item.options.body.outline_generated;
+    let mut contents = item.to_token_stream();
+    if outline_generated.is_some() {
+        contents = crate::outline_generated(contents, "hdl-bundle-");
+    }
+    Ok(contents)
+}

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

@@ -0,0 +1,6 @@
+use proc_macro2::TokenStream;
+use syn::ItemEnum;
+
+pub(crate) fn hdl_enum(item: ItemEnum) -> syn::Result<TokenStream> {
+    todo!()
+}

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

@@ -0,0 +1,70 @@
+use crate::{fold::impl_fold, kw};
+use proc_macro2::{Span, TokenStream};
+use quote::{quote, quote_spanned, ToTokens};
+use syn::{
+    parse::{Parse, ParseStream},
+    parse_quote_spanned,
+    punctuated::Punctuated,
+    token::Paren,
+    Attribute, Ident, Path, Token, WhereClause, WherePredicate,
+};
+
+crate::options! {
+    #[options = TypeOptions]
+    pub(crate) enum TypeOption {
+        OutlineGenerated(outline_generated),
+        ConnectInexact(connect_inexact),
+        Target(target, Path),
+    }
+}
+
+pub(crate) struct WrappedInConst<'a> {
+    outer: &'a mut TokenStream,
+    span: Span,
+    inner: TokenStream,
+}
+
+impl<'a> WrappedInConst<'a> {
+    pub(crate) fn new(outer: &'a mut TokenStream, span: Span) -> Self {
+        Self {
+            outer,
+            span,
+            inner: TokenStream::new(),
+        }
+    }
+    pub(crate) fn inner(&mut self) -> &mut TokenStream {
+        &mut self.inner
+    }
+}
+
+impl Drop for WrappedInConst<'_> {
+    fn drop(&mut self) {
+        let inner = &self.inner;
+        quote_spanned! {self.span=>
+            const _: () = {
+                #inner
+            };
+        }
+        .to_tokens(self.outer);
+    }
+}
+
+pub(crate) fn get_target(target: &Option<(kw::target, Paren, Path)>, item_ident: &Ident) -> Path {
+    match target {
+        Some((_, _, target)) => target.clone(),
+        None => item_ident.clone().into(),
+    }
+}
+
+pub(crate) fn common_derives(span: Span) -> Attribute {
+    parse_quote_spanned! {span=>
+        #[::fayalite::__std::prelude::v1::derive(
+            ::fayalite::__std::fmt::Debug,
+            ::fayalite::__std::cmp::Eq,
+            ::fayalite::__std::cmp::PartialEq,
+            ::fayalite::__std::hash::Hash,
+            ::fayalite::__std::marker::Copy,
+            ::fayalite::__std::clone::Clone,
+        )]
+    }
+}

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

@@ -13,6 +13,9 @@ use syn::{
 };
 
 mod fold;
+mod hdl_bundle;
+mod hdl_enum;
+mod hdl_type_common;
 mod module;
 mod value_derive_common;
 mod value_derive_enum;
@@ -728,3 +731,15 @@ pub fn value_derive(item: TokenStream) -> syn::Result<TokenStream> {
         )),
     }
 }
+
+pub fn hdl_attr(attr: TokenStream, item: TokenStream) -> syn::Result<TokenStream> {
+    let item = syn::parse2::<Item>(quote! { #[hdl(#attr)] #item })?;
+    match item {
+        Item::Enum(item) => hdl_enum::hdl_enum(item),
+        Item::Struct(item) => hdl_bundle::hdl_bundle(item),
+        _ => Err(syn::Error::new(
+            Span::call_site(),
+            "top-level #[hdl] can only be used on structs or enums",
+        )),
+    }
+}

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

@@ -1290,7 +1290,10 @@ impl Visitor {
                 memory,
                 paren,
                 ty_expr,
-            } => (paren, unwrap_or_static_type(ty_expr.as_ref(), memory.span())),
+            } => (
+                paren,
+                unwrap_or_static_type(ty_expr.as_ref(), memory.span()),
+            ),
             MemoryFn::MemoryArray {
                 memory_array,
                 paren,