Support Generic arguments to Structs

This removes StructFieldType from the TyTy base as it is not a type that
can be unified against.

It adds in a substition mapper implementation which will likely change
over time when this this support is extended over to Functions and
TupleStructs.

Note generic argument binding is not supported as part of this yet.

Fixes #235

1 files changed, 10 insertions, 2 deletions

diff --git a/gcc/rust/backend/rust-compile-context.h b/gcc/rust/backend/rust-compile-context.h
index c5ae3bb..b191554 100644
--- a/gcc/rust/backend/rust-compile-context.h
+++ b/gcc/rust/backend/rust-compile-context.h
@@ -274,7 +274,15 @@ public:
 
   void visit (TyTy::InferType &) override { gcc_unreachable (); }
 
-  void visit (TyTy::StructFieldType &) override { gcc_unreachable (); }
+  void visit (TyTy::ParamType &param) override
+  {
+    rust_assert (param.get_ref () != param.get_ty_ref ());
+
+    TyTy::BaseType *lookup = nullptr;
+    bool ok = ctx->get_tyctx ()->lookup_type (param.get_ty_ref (), &lookup);
+    rust_assert (ok);
+    lookup->accept_vis (*this);
+  }
 
   void visit (TyTy::FnType &type) override
   {
@@ -338,7 +346,7 @@ public:
     Btype *named_struct
       = ctx->get_backend ()->named_type (type.get_name (), struct_type_record,
 					 ctx->get_mappings ()->lookup_location (
-					   type.get_ty_ref ()));
+					   type.get_ref ()));
 
     ctx->push_type (named_struct);
     ctx->insert_compiled_type (type.get_ty_ref (), named_struct);