[clang] [C23][Parser] Diagnostic for attribute declaration where statement is required (PR #146224)

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@@ -159,6 +159,7 @@ def BuiltinRequiresHeader : DiagGroup<"builtin-requires-header">;
 def C99Compat : DiagGroup<"c99-compat">;
 def C23Compat : DiagGroup<"c23-compat">;
 def : DiagGroup<"c2x-compat", [C23Compat]>;
+def CAttributeExtensions : DiagGroup<"c-attribute-extension">;
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yronglin wrote:

removed

https://github.com/llvm/llvm-project/pull/146224