[ObjC generics] Fix not inheriting type bounds in categories/extensions.

When a category/extension doesn't repeat a type bound, corresponding
type parameter is substituted with `id` when used as a type argument. As
a result, in the added test case it was causing errors like

> type argument 'T' (aka 'id') does not satisfy the bound ('id<NSCopying>') of type parameter 'T'

We are already checking that type parameters should be consistent
everywhere (see `checkTypeParamListConsistency`) and update
`ObjCTypeParamDecl` to have correct underlying type. And when we use the
type parameter as a method return type or a method parameter type, it is
substituted to the bounded type. But when we use the type parameter as a
type argument, we check `ObjCTypeParamType` that ignores the updated
underlying type and remains `id`.

Fix by desugaring `ObjCTypeParamType` to the underlying type, the same
way we are doing with `TypedefType`.

rdar://problem/54329242

Reviewers: erik.pilkington, ahatanak

Reviewed By: erik.pilkington

Subscribers: jkorous, dexonsmith, ributzka, cfe-commits

Differential Revision: https://reviews.llvm.org/D66696


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374202 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 1 deletions

diff --git a/include/clang/AST/Type.h b/include/clang/AST/Type.h
index ecbbd73e19..c9238e9521 100644
--- a/include/clang/AST/Type.h
+++ b/include/clang/AST/Type.h
@@ -5569,7 +5569,7 @@ class ObjCTypeParamType : public Type,
 
 public:
   bool isSugared() const { return true; }
-  QualType desugar() const { return getCanonicalTypeInternal(); }
+  QualType desugar() const;
 
   static bool classof(const Type *T) {
     return T->getTypeClass() == ObjCTypeParam;