[clang] [clang] fix RecursiveASTVisitor traversal from type to decl (PR #132551)

[Andrey Ali Khan Bolshakov via cfe-commits]

bolshakov-a wrote:

Thanks, it becomes now clearer for me. However, I'm still not succeeded in making this code really working, because the default version of `TraverseDecltypeType` doesn't traverse the underlying desugared type:
https://github.com/llvm/llvm-project/blob/be6ccc98f38227db02164f17bfaf0ac86d800e4a/clang/include/clang/AST/RecursiveASTVisitor.h#L1101-L1102
But, maybe, if someone provides his own version of `TraverseDecltypeType` in his visitor, then this may become useful...

My primary concern is that one may think that `NestedNameSpecifier` node is now always inserted between `MemberPointerType` and its class type node, but it may be not the case, and under very specific conditions.

By the way, it looks strange for me that `int Typedef::*` is not considered as a sugar.

https://github.com/llvm/llvm-project/pull/132551