Handle generic Slices and Arrays

Slices and Arrays are covariant types which means they can contain elements
which bind generics such as ADT or FnTypes. This means substitutions can be
recursive and this gives the typechecker a chance to handle this recursion
on these types.

Author: philberty

gcc/rust/typecheck/rust-substitution-mapper.h

@@ -221,11 +221,19 @@ class SubstMapperInternal : public TyTy::TyVisitor
     resolved = type.handle_substitions (mappings);
   }
 
+  void visit (TyTy::ArrayType &type) override
+  {
+    resolved = type.handle_substitions (mappings);
+  }
+
+  void visit (TyTy::SliceType &type) override
+  {
+    resolved = type.handle_substitions (mappings);
+  }
+
   // nothing to do for these
   void visit (TyTy::InferType &) override { gcc_unreachable (); }
   void visit (TyTy::FnPtr &) override { gcc_unreachable (); }
-  void visit (TyTy::ArrayType &) override { gcc_unreachable (); }
-  void visit (TyTy::SliceType &) override { gcc_unreachable (); }
   void visit (TyTy::BoolType &) override { gcc_unreachable (); }
   void visit (TyTy::IntType &) override { gcc_unreachable (); }
   void visit (TyTy::UintType &) override { gcc_unreachable (); }

gcc/rust/typecheck/rust-tyty.cc

@@ -1508,6 +1508,22 @@ ArrayType::clone () const
 			element_type, get_combined_refs ());
 }
 
+ArrayType *
+ArrayType::handle_substitions (SubstitutionArgumentMappings mappings)
+{
+  auto mappings_table = Analysis::Mappings::get ();
+
+  ArrayType *ref = static_cast<ArrayType *> (clone ());
+  ref->set_ty_ref (mappings_table->get_next_hir_id ());
+
+  // might be &T or &ADT so this needs to be recursive
+  auto base = ref->get_element_type ();
+  BaseType *concrete = Resolver::SubstMapperInternal::Resolve (base, mappings);
+  ref->element_type = TyVar (concrete->get_ty_ref ());
+
+  return ref;
+}
+
 void
 SliceType::accept_vis (TyVisitor &vis)
 {
@@ -1581,6 +1597,22 @@ SliceType::clone () const
 			get_combined_refs ());
 }
 
+SliceType *
+SliceType::handle_substitions (SubstitutionArgumentMappings mappings)
+{
+  auto mappings_table = Analysis::Mappings::get ();
+
+  SliceType *ref = static_cast<SliceType *> (clone ());
+  ref->set_ty_ref (mappings_table->get_next_hir_id ());
+
+  // might be &T or &ADT so this needs to be recursive
+  auto base = ref->get_element_type ();
+  BaseType *concrete = Resolver::SubstMapperInternal::Resolve (base, mappings);
+  ref->element_type = TyVar (concrete->get_ty_ref ());
+
+  return ref;
+}
+
 void
 BoolType::accept_vis (TyVisitor &vis)
 {

gcc/rust/typecheck/rust-tyty.h

@@ -1665,6 +1665,8 @@ class ArrayType : public BaseType
 
   HIR::Expr &get_capacity_expr () const { return capacity_expr; }
 
+  ArrayType *handle_substitions (SubstitutionArgumentMappings mappings);
+
 private:
   TyVar element_type;
   HIR::Expr &capacity_expr;
@@ -1710,6 +1712,8 @@ class SliceType : public BaseType
     return get_element_type ()->is_concrete ();
   }
 
+  SliceType *handle_substitions (SubstitutionArgumentMappings mappings);
+
 private:
   TyVar element_type;
 };