[all-commits] [llvm/llvm-project] ccc4d8: [ObjC] Diagnose implicit type coercion from ObjC '...

[jyknight via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: ccc4d83cda16bea1d9dfd0967dc7d2cfb24b8e75
      https://github.com/llvm/llvm-project/commit/ccc4d83cda16bea1d9dfd0967dc7d2cfb24b8e75
  Author: James Y Knight <jyknight at google.com>
  Date:   2019-10-17 (Thu, 17 Oct 2019)

  Changed paths:
    M clang/lib/AST/ASTContext.cpp
    M clang/lib/Sema/SemaExpr.cpp
    M clang/test/SemaObjC/comptypes-1.m
    M clang/test/SemaObjCXX/class-method-self.mm
    M clang/test/SemaObjCXX/comptypes-1.mm
    M clang/test/SemaObjCXX/comptypes-7.mm
    M clang/test/SemaObjCXX/instancetype.mm

  Log Message:
  -----------
  [ObjC] Diagnose implicit type coercion from ObjC 'Class' to object
pointer types.

For example, in Objective-C mode, the initialization of 'x' in:
```
  @implementation MyType
  + (void)someClassMethod {
    MyType *x = self;
  }
  @end
```
is correctly diagnosed with an incompatible-pointer-types warning, but
in Objective-C++ mode, it is not diagnosed at all -- even though
incompatible pointer conversions generally become an error in C++.

This patch fixes that oversight, allowing implicit conversions
involving Class only to/from unqualified-id, and between qualified and
unqualified Class, where the protocols are compatible.

Note that this does change some behaviors in Objective-C, as well, as
shown by the modified tests.

Of particular note is that assignment from from 'Class<MyProtocol>' to
'id<MyProtocol>' now warns. (Despite appearances, those are not
compatible types. 'Class<MyProtocol>' is not expected to have instance
methods defined by 'MyProtocol', while 'id<MyProtocol>' is.)

Differential Revision: https://reviews.llvm.org/D67983

llvm-svn: 375125