[Clang] Fix __{add,remove}_pointer in Objective-C++ (#123678)

This aligns the builtins with how implementations work which don't use
the buitins.

Author: philnik777

clang/docs/ReleaseNotes.rst

@@ -122,6 +122,8 @@ Bug Fixes in This Version
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- The behvaiour of ``__add_pointer`` and ``__remove_pointer`` for Objective-C++'s ``id`` and interfaces has been fixed.
+
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

clang/lib/Sema/SemaType.cpp

@@ -1826,7 +1826,8 @@ QualType Sema::BuildPointerType(QualType T,
   if (checkQualifiedFunction(*this, T, Loc, QFK_Pointer))
     return QualType();
 
-  assert(!T->isObjCObjectType() && "Should build ObjCObjectPointerType");
+  if (T->isObjCObjectType())
+    return Context.getObjCObjectPointerType(T);
 
   // In ARC, it is forbidden to build pointers to unqualified pointers.
   if (getLangOpts().ObjCAutoRefCount)
@@ -9807,8 +9808,7 @@ QualType Sema::BuiltinAddPointer(QualType BaseType, SourceLocation Loc) {
 }
 
 QualType Sema::BuiltinRemovePointer(QualType BaseType, SourceLocation Loc) {
-  // We don't want block pointers or ObjectiveC's id type.
-  if (!BaseType->isAnyPointerType() || BaseType->isObjCIdType())
+  if (!BaseType->isAnyPointerType())
     return BaseType;
 
   return BaseType->getPointeeType();

clang/test/SemaCXX/remove_pointer.mm

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsyntax-only -verify -std=c++17  %s
+
+// expected-no-diagnostics
+
+@interface I;
+@end
+
+@class C;
+
+static_assert(__is_same(__add_pointer(id), id*));
+static_assert(__is_same(__add_pointer(I), I*));
+
+static_assert(__is_same(__remove_pointer(C*), C));
+static_assert(!__is_same(__remove_pointer(id), id));
+static_assert(__is_same(__remove_pointer(id*), id));
+static_assert(__is_same(__remove_pointer(__add_pointer(id)), id));
+static_assert(__is_same(__add_pointer(__remove_pointer(id)), id));