add #[hdl(get(|v| ...))] type GetStuff<P: PhantomConstGet<MyStruct>> = MyType or DynSize;

crates/fayalite/src/phantom_const.rs

@@ -415,3 +415,71 @@ impl<T: ?Sized + PhantomConstValue> ToSimValueWithType<CanonicalType> for Phanto
         SimValue::into_canonical(SimValue::from_value(Self::from_canonical(ty), *self))
     }
 }
+
+mod sealed {
+    pub trait Sealed<T: ?Sized> {}
+}
+
+pub trait PhantomConstGet<T: ?Sized + PhantomConstValue>: sealed::Sealed<T> {
+    fn get(&self) -> Interned<T>;
+}
+
+impl<T: ?Sized + PhantomConstValue, This: ?Sized + std::ops::Deref<Target: PhantomConstGet<T>>>
+    sealed::Sealed<T> for This
+{
+}
+
+impl<T: ?Sized + PhantomConstValue, This: ?Sized + std::ops::Deref<Target: PhantomConstGet<T>>>
+    PhantomConstGet<T> for This
+{
+    fn get(&self) -> Interned<T> {
+        This::Target::get(&**self)
+    }
+}
+
+macro_rules! impl_phantom_const_get {
+    (
+        impl PhantomConstGet<$T:ident> for $ty:ty {
+            fn $get:ident(&$get_self:ident) -> _ $get_body:block
+        }
+    ) => {
+        impl<$T: ?Sized + PhantomConstValue> sealed::Sealed<$T> for $ty {}
+
+        impl<$T: ?Sized + PhantomConstValue> PhantomConstGet<$T> for $ty {
+            fn $get(&$get_self) -> Interned<$T> $get_body
+        }
+    };
+}
+
+impl_phantom_const_get! {
+    impl PhantomConstGet<T> for PhantomConst<T> {
+        fn get(&self) -> _ {
+            PhantomConst::get(*self)
+        }
+    }
+}
+
+impl_phantom_const_get! {
+    impl PhantomConstGet<T> for Expr<PhantomConst<T>> {
+        fn get(&self) -> _ {
+            PhantomConst::get(Expr::ty(*self))
+        }
+    }
+}
+
+#[doc(hidden)]
+pub trait ReturnSelfUnchanged<T: ?Sized> {
+    type Type: ?Sized;
+}
+
+impl<This: ?Sized, T: ?Sized> ReturnSelfUnchanged<T> for This {
+    type Type = This;
+}
+
+#[doc(hidden)]
+pub fn type_alias_phantom_const_get_helper<T: ?Sized + PhantomConstValue, R: Intern + Clone>(
+    param: impl PhantomConstGet<T>,
+    get: impl FnOnce(Interned<T>) -> R,
+) -> &'static R {
+    Interned::into_inner(get(param.get()).intern_sized())
+}

crates/fayalite/src/prelude.rs

@@ -27,7 +27,7 @@ pub use crate::{
         Instance, Module, ModuleBuilder, annotate, connect, connect_any, incomplete_wire, instance,
         memory, memory_array, memory_with_init, reg_builder, wire,
     },
-    phantom_const::PhantomConst,
+    phantom_const::{PhantomConst, PhantomConstGet},
     platform::{DynPlatform, Platform, PlatformIOBuilder, peripherals},
     reg::Reg,
     reset::{AsyncReset, Reset, SyncReset, ToAsyncReset, ToReset, ToSyncReset},

crates/fayalite/tests/hdl_types.rs

@@ -4,7 +4,6 @@ use fayalite::{
     bundle::BundleType,
     enum_::EnumType,
     int::{BoolOrIntType, IntType},
-    phantom_const::PhantomConst,
     prelude::*,
     ty::StaticType,
 };
@@ -197,3 +196,21 @@ check_bounds!(CheckBoundsTTT2<#[a, Type] A: BundleType +, #[b, Type] B: Type +,
 check_bounds!(CheckBoundsTTT3<#[a, Type] A: EnumType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
 check_bounds!(CheckBoundsTTT4<#[a, Type] A: IntType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
 check_bounds!(CheckBoundsTTT5<#[a, Type] A: StaticType +, #[b, Type] B: Type +, #[c, Type] C: Type +>);
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug, serde::Serialize, serde::Deserialize)]
+pub struct MyPhantomConstInner {
+    pub a: usize,
+    pub b: UInt,
+}
+
+#[hdl(outline_generated, get(|v| v.a))]
+pub type GetA<P: PhantomConstGet<MyPhantomConstInner>> = DynSize;
+
+#[hdl(outline_generated, get(|v| v.b))]
+pub type GetB<P: PhantomConstGet<MyPhantomConstInner>> = UInt;
+
+#[hdl(outline_generated, no_static)]
+pub struct MyTypeWithPhantomConstParameter<P: Type + PhantomConstGet<MyPhantomConstInner>> {
+    pub a: ArrayType<Bool, GetA<P>>,
+    pub b: HdlOption<GetB<P>>,
+}