[clang] [Clang] Fix Microsoft ABI inheritance model when member pointer is used in a base specifier (PR #91990)

[Reid Kleckner via cfe-commits]

================
@@ -13,3 +15,18 @@ template <typename T>
 struct S3 {
   int T::*foo;
 };
+
+template<int I> struct Base {};
+struct
+S5 // #S5
+:
+Base<sizeof(int S5::*)>
+// expected-error at -1 {{member pointer has incomplete base type 'S5'}}
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rnk wrote:

I agree on the desired behavior, but doesn't this test show that, in the MS ABI mode, clang emits a hard error about an incomplete type? That's my reading of what the code does, and what the test shows.

https://github.com/llvm/llvm-project/pull/91990