[clang] improve class type sugar preservation in pointers to members (#130537)

This changes the MemberPointerType representation to use a
NestedNameSpecifier instead of a Type to represent the class.

Since the qualifiers are always parsed as nested names, there was an
impedance mismatch when converting these back and forth into types, and
this led to issues in preserving sugar.

The nested names are indeed a better match for these, as the differences
which a QualType can represent cannot be expressed syntactically, and it
also represents the use case more exactly, being either dependent or
referring to a CXXRecord, unqualified.

This patch also makes the MemberPointerType able to represent sugar for
a {up/downcast}cast conversion of the base class, although for now the
underlying type is canonical, as preserving the sugar up to that point
requires further work.

As usual, includes a few drive-by fixes in order to make use of the
improvements, and removing some duplications, for example
CheckBaseClassAccess is deduplicated from across SemaAccess and
SemaCast.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index f88d620..e26c6c3 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2667,7 +2667,7 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
     for (const CXXRecordDecl *Base : getMostBaseClasses(MD->getParent())) {
       llvm::Metadata *Id =
           CreateMetadataIdentifierForType(Context.getMemberPointerType(
-              MD->getType(), Context.getRecordType(Base).getTypePtr()));
+              MD->getType(), /*Qualifier=*/nullptr, Base));
       F->addTypeMetadata(0, Id);
     }
   }