[clang] [clang] move -Wcast-function-type under -Wextra (PR #77178)

[Vlad Serebrennikov via cfe-commits]

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@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 %s -fsyntax-only -Wextra -verify
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Endilll wrote:

As written, tests checks only default language mode for C (which is `gnu99` AFAIK). Maybe we want to check other modes as well? 

https://github.com/llvm/llvm-project/pull/77178