[clang] [llvm] [clang-tools-extra] [compiler-rt] [flang] [libcxx] [Clang][Sema] Fix qualifier restriction of overriden methods (PR #71696)

[Aaron Ballman via cfe-commits]

================
@@ -289,3 +289,29 @@ namespace PR8168 {
     static void foo() {} // expected-error{{'static' member function 'foo' overrides a virtual function}}
   };
 }
+
+namespace T13 {
----------------
AaronBallman wrote:

I'd like to see additional test cases involving type aliases with and without qualifiers. e.g.,
```
namespace T13 {
  using cip = const int *;
  using ip = int *;

  class A {
  public:
    virtual const int *foo();
    virtual const int *bar();
    virtual const int *baz();
    virtual const int *quux();
  };

  class B: public A {
  public:
    cip foo() override; // Okay
    const int *bar() override; // Okay
    int *baz() override; // Diagnosed
    ip quux() override; // Diagnosed
  };
}
```
and similar for the class-based tests.

https://github.com/llvm/llvm-project/pull/71696