[clang] [Clang] Add [[clang::diagnose_specializations]] (PR #101469)

[via cfe-commits]

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@@ -5407,6 +5407,9 @@ def note_dependent_function_template_spec_discard_reason : Note<
   "candidate ignored: %select{not a function template|"
   "not a member of the enclosing %select{class template|"
   "namespace; did you mean to explicitly qualify the specialization?}1}0">;
+def warn_diag_specialization : Warning<
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Sirraide wrote:

nit: `warn_diag_...` is a bit of a weird name for a diagnostic. Can we call this just `warn_invalid_specialization` or sth like that?

https://github.com/llvm/llvm-project/pull/101469