[Clang][Sema] Fix crash with const qualified member operator new

We should diagnose a const qualified member operator new but we fail to do so
and this leads to crash during debug info generation.

The fix is to diagnose this as ill-formed in the front-end.

Fixes: llvm#79748

clang/lib/Sema/SemaType.cpp

@@ -5914,8 +5914,10 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
     //
     // ... for instance.
     if (IsQualifiedFunction &&
-        !(Kind == Member && !D.isExplicitObjectMemberFunction() &&
-          D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static) &&
+        (Kind != Member || D.isExplicitObjectMemberFunction() ||
+         D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static ||
+         (D.getContext() == clang::DeclaratorContext::Member &&
+          D.isStaticMember())) &&
         !IsTypedefName && D.getContext() != DeclaratorContext::TemplateArg &&
         D.getContext() != DeclaratorContext::TemplateTypeArg) {
       SourceLocation Loc = D.getBeginLoc();

clang/test/SemaCXX/function-type-qual.cpp

@@ -37,3 +37,9 @@ void instantiateArrayDecay() {
   int a[1];
   arrayDecay(a);
 }
+
+namespace GH79748 {
+struct A {
+  void* operator new(unsigned long bytes) const; //expected-error {{static member function cannot have 'const' qualifier}}
+};
+}