Constify the Backend resolve compile interface

This is a bad name for this class, but it will compile a TyTy type into a
GCC Backend::Btype* node. The class also tries to determine if we have
already compiled this node for monomorphization and canonicalization of
types which will avoid unnessecary conversion code based on type equality.

This patch simply makes this a const visitor to enforce pointer ownership
rules.

1 files changed, 26 insertions, 27 deletions

diff --git a/gcc/rust/backend/rust-compile-context.h b/gcc/rust/backend/rust-compile-context.h
index 0da2198..fd2c0b5 100644
--- a/gcc/rust/backend/rust-compile-context.h
+++ b/gcc/rust/backend/rust-compile-context.h
@@ -340,10 +340,10 @@ private:
   std::vector<::Bfunction *> func_decls;
 };
 
-class TyTyResolveCompile : public TyTy::TyVisitor
+class TyTyResolveCompile : public TyTy::TyConstVisitor
 {
 public:
-  static ::Btype *compile (Context *ctx, TyTy::BaseType *ty,
+  static ::Btype *compile (Context *ctx, const TyTy::BaseType *ty,
 			   bool trait_object_mode = false)
   {
     TyTyResolveCompile compiler (ctx, trait_object_mode);
@@ -351,26 +351,25 @@ public:
     return compiler.translated;
   }
 
-  void visit (TyTy::ErrorType &) override { gcc_unreachable (); }
+  void visit (const TyTy::ErrorType &) override { gcc_unreachable (); }
+  void visit (const TyTy::InferType &) override { gcc_unreachable (); }
 
-  void visit (TyTy::InferType &) override { gcc_unreachable (); }
-
-  void visit (TyTy::ProjectionType &type) override
+  void visit (const TyTy::ProjectionType &type) override
   {
     type.get ()->accept_vis (*this);
   }
 
-  void visit (TyTy::PlaceholderType &type) override
+  void visit (const TyTy::PlaceholderType &type) override
   {
     type.resolve ()->accept_vis (*this);
   }
 
-  void visit (TyTy::ParamType &param) override
+  void visit (const TyTy::ParamType &param) override
   {
     param.resolve ()->accept_vis (*this);
   }
 
-  void visit (TyTy::FnType &type) override
+  void visit (const TyTy::FnType &type) override
   {
     Backend::Btyped_identifier receiver;
     std::vector<Backend::Btyped_identifier> parameters;
@@ -409,7 +408,7 @@ public:
 	ctx->get_mappings ()->lookup_location (type.get_ref ()));
   }
 
-  void visit (TyTy::FnPtr &type) override
+  void visit (const TyTy::FnPtr &type) override
   {
     Btype *result_type
       = TyTyResolveCompile::compile (ctx, type.get_return_type ());
@@ -426,7 +425,7 @@ public:
       ctx->get_mappings ()->lookup_location (type.get_ref ()));
   }
 
-  void visit (TyTy::ADTType &type) override
+  void visit (const TyTy::ADTType &type) override
   {
     if (ctx->lookup_compiled_types (type.get_ty_ref (), &translated, &type))
       return;
@@ -434,7 +433,7 @@ public:
     std::vector<Backend::Btyped_identifier> fields;
     for (size_t i = 0; i < type.num_fields (); i++)
       {
-	TyTy::StructFieldType *field = type.get_field (i);
+	const TyTy::StructFieldType *field = type.get_field (i);
 	Btype *compiled_field_ty
 	  = TyTyResolveCompile::compile (ctx, field->get_field_type ());
 
@@ -460,7 +459,7 @@ public:
     ctx->insert_compiled_type (type.get_ty_ref (), named_struct, &type);
   }
 
-  void visit (TyTy::TupleType &type) override
+  void visit (const TyTy::TupleType &type) override
   {
     if (type.num_fields () == 0)
       {
@@ -504,7 +503,7 @@ public:
     translated = named_struct;
   }
 
-  void visit (TyTy::ArrayType &type) override
+  void visit (const TyTy::ArrayType &type) override
   {
     Btype *element_type
       = TyTyResolveCompile::compile (ctx, type.get_element_type ());
@@ -512,7 +511,7 @@ public:
       = ctx->get_backend ()->array_type (element_type, type.get_capacity ());
   }
 
-  void visit (TyTy::BoolType &type) override
+  void visit (const TyTy::BoolType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -520,7 +519,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::IntType &type) override
+  void visit (const TyTy::IntType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -528,7 +527,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::UintType &type) override
+  void visit (const TyTy::UintType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -536,7 +535,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::FloatType &type) override
+  void visit (const TyTy::FloatType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -544,7 +543,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::USizeType &type) override
+  void visit (const TyTy::USizeType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -552,7 +551,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::ISizeType &type) override
+  void visit (const TyTy::ISizeType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -560,7 +559,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::CharType &type) override
+  void visit (const TyTy::CharType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -568,7 +567,7 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::ReferenceType &type) override
+  void visit (const TyTy::ReferenceType &type) override
   {
     Btype *base_compiled_type
       = TyTyResolveCompile::compile (ctx, type.get_base (), trait_object_mode);
@@ -583,7 +582,7 @@ public:
       }
   }
 
-  void visit (TyTy::PointerType &type) override
+  void visit (const TyTy::PointerType &type) override
   {
     Btype *base_compiled_type
       = TyTyResolveCompile::compile (ctx, type.get_base (), trait_object_mode);
@@ -598,7 +597,7 @@ public:
       }
   }
 
-  void visit (TyTy::StrType &type) override
+  void visit (const TyTy::StrType &type) override
   {
     ::Btype *compiled_type = nullptr;
     bool ok = ctx->lookup_compiled_types (type.get_ty_ref (), &compiled_type);
@@ -606,12 +605,12 @@ public:
     translated = compiled_type;
   }
 
-  void visit (TyTy::NeverType &) override
+  void visit (const TyTy::NeverType &) override
   {
     translated = ctx->get_backend ()->unit_type ();
   }
 
-  void visit (TyTy::DynamicObjectType &type) override
+  void visit (const TyTy::DynamicObjectType &type) override
   {
     if (trait_object_mode)
       {
@@ -661,7 +660,7 @@ public:
     ctx->insert_compiled_type (type.get_ty_ref (), named_struct, &type);
   }
 
-  void visit (TyTy::ClosureType &type) override { gcc_unreachable (); }
+  void visit (const TyTy::ClosureType &type) override { gcc_unreachable (); }
 
 private:
   TyTyResolveCompile (Context *ctx, bool trait_object_mode)