[clang] [Clang] disallow attributes on void parameters (PR #124920)

[Erich Keane via cfe-commits]

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@@ -3832,6 +3832,9 @@ def warn_type_attribute_wrong_type : Warning<
   "'%0' only applies to %select{function|pointer|"
   "Objective-C object or block pointer}1 types; type here is %2">,
   InGroup<IgnoredAttributes>;
+def warn_attribute_on_void_param: Warning<
+  "attribute %0 cannot be applied to a 'void' parameter">,
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erichkeane wrote:

Is `'void' parameter` technically correct here?  Isn't `(void)` technically an empty parameter list?  Can we word this better, or are we ok with the term?

https://github.com/llvm/llvm-project/pull/124920