[clang] [Clang][Sema] Implement proposed resolution for CWG2847 (PR #80899)

[Vlad Serebrennikov via cfe-commits]

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@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -std=c++20 -verify=expected %s
+
+namespace dr2847 { // dr2847: 19
+
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Endilll wrote:

`#if __cplusplus >= 202302L` skips over C++20, which doesn't seem intentional given the previous iteration of this PR I reviewed. I also put this comment on this specific lines, as we put `#if __cplusplus` checks inside namespace each test have, so that they are as independent as possible.

https://github.com/llvm/llvm-project/pull/80899