[PATCH] D72872: [ObjC generics] Fix not inheriting type bounds in categories/extensions.

[Volodymyr Sapsai via Phabricator via cfe-commits]

vsapsai created this revision.
vsapsai added reviewers: erik.pilkington, ahatanak.
Herald added subscribers: ributzka, dexonsmith, jkorous.
Herald added a project: clang.

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 wasn't updated and
remains `id`.

Fix by updating not only `ObjCTypeParamDecl` UnderlyingType but also
TypeForDecl as we use the underlying type to create a canonical type for
`ObjCTypeParamType` (see `ASTContext::getObjCTypeParamType`).

This is a different approach to fixing the issue. The previous one was
02c2ab3d8872416589bd1a6ca3dfb96ba373a3b9 which was reverted in
4c539e8da1b3de38a53ef3f7497f5c45a3243b61. The problem with the previous
approach was that `ObjCTypeParamType::desugar` was returning underlying
type for `ObjCTypeParamDecl` without applying any protocols stored in
`ObjCTypeParamType`. It caused inconsistencies in comparing types before
and after desugaring.

rdar://problem/54329242


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D72872

Files:
  clang/include/clang/AST/ASTContext.h
  clang/lib/AST/ASTContext.cpp
  clang/lib/AST/Type.cpp
  clang/lib/Sema/SemaDeclObjC.cpp
  clang/test/SemaObjC/parameterized_classes_collection_literal.m
  clang/test/SemaObjC/parameterized_classes_subst.m

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