[clang] [clang] Fix assertion crash in alloc_size structural equivalence check (#199407) (PR #199980)

[Shafik Yaghmour via cfe-commits]

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@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -std=c23 -fsyntax-only -verify %s
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shafik wrote:

I think `clang/test/Sema/alloc-size.c ` is a better home for this test and maybe name the macro GH199407 or add a comment explaining it is a regression test for GH199407.

https://github.com/llvm/llvm-project/pull/199980