[clang] [Clang][Sema] Diagnose variable template explicit specializations with storage-class-specifiers (PR #93873)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

> I've been hinted though that Clang may be incorrect in accepting explicit specializations of a templated static class data member in the class scope. It looks like with all the restrictions in the standard it may only be allowed to place explicit specializations of a templated static class data member outside of the class.

@alexfh What makes you say that? I think the resolution of [CWG727](https://cplusplus.github.io/CWG/issues/727.html) quite clearly permits class scope explicit specializations of function templates, class templates, and static data member templates.

https://github.com/llvm/llvm-project/pull/93873