[clang] [clang] Implement CWG2877 "Type-only lookup for using-enum-declarator" (PR #95399)

[Vlad Serebrennikov via cfe-commits]

================
@@ -148,13 +148,10 @@ template <int I> struct C {
   enum class D { d,
                  e,
                  f };
-  using enum D;
-
-  static constexpr int W = int(f) + I;
+  using enum D; // expected-error {{using-enum cannot name a dependent type}}
----------------
Endilll wrote:

Yes. I first implemented the DR, ran the tests, and this one failed. Then I realized that this test was incorrect.

https://github.com/llvm/llvm-project/pull/95399