[clang] [clang] When checking for covariant return types, make sure the pointers or references are to *classes* (PR #111856)

[Ilya Biryukov via cfe-commits]

================
@@ -289,3 +289,13 @@ namespace PR8168 {
     static void foo() {} // expected-error{{'static' member function 'foo' overrides a virtual function}}
   };
 }
+
+namespace T13 {
+  struct A {
+    virtual const int *f() const; // expected-note{{overridden virtual function is here}}
+  };
+
+  struct B : A {
+    int *f() const override; // expected-error{{virtual function 'f' has a different return type ('int *') than the function it overrides (which has return type 'const int *')}}
+  };
+}
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ilya-biryukov wrote:

Given that the code has a different treatment of types which are pointers and references, having a variation of `T2` with non-class types seems valuable. (we could probably add it to `T2` directly).

Same for qualification in `T6`, given that the rules are special for the class types.

https://github.com/llvm/llvm-project/pull/111856