[clang] [Clang][Sema] Diagnose use of template keyword after declarative nested-name-specifiers (PR #78595)

[Vlad Serebrennikov via cfe-commits]

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@@ -182,8 +182,8 @@ struct Bad2 { int a, b; };
 } // namespace dr2386
 namespace std {
 template <typename T> struct tuple_size;
-template <> struct std::tuple_size<dr2386::Bad1> {};
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Endilll wrote:

Is this warning emitted if we spell it `::std::tuple)size`?

https://github.com/llvm/llvm-project/pull/78595