[Sema] Add MacroQualified case for FunctionTypeUnwrapper

This is a fix for PR43315. An assertion error is hit for this minimal example:

```
//clang -cc1 -triple x86_64-- -S tstVMStructRC-min.cpp
int (a b)();  // Assertion `Chunk.Kind == DeclaratorChunk::Function' failed.
```

This is because we do not cover the case in the FunctionTypeUnwrapper where it
receives a MacroQualifiedType. We have not run into this earlier because this
is a unique case where the __attribute__ contains both __cdecl__ and
__regparm__ (in that order), and we are compiling for x86_64. Changing the
architecture or the order of __cdecl__ and __regparm__ does not raise the
assertion.

Differential Revision: https://reviews.llvm.org/D67992

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/test/Frontend/macro_defined_type.cpp b/clang/test/Frontend/macro_defined_type.cpp
index d4f54b65a8d..71a0ff18477 100644
--- a/clang/test/Frontend/macro_defined_type.cpp
+++ b/clang/test/Frontend/macro_defined_type.cpp
@@ -19,3 +19,7 @@ void Func() {
 struct A {
   _LIBCPP_FLOAT_ABI int operator()() throw(); // expected-warning{{'pcs' calling convention is not supported for this target}}
 };
+
+// Added test for fix for PR43315
+#define a __attribute__((__cdecl__, __regparm__(0)))
+int(a b)();