[clang] [clang] Reapply Handle templated operators with reversed arguments (PR #72213)

[Ilya Biryukov via cfe-commits]

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@@ -37,6 +37,27 @@ These changes are ones which we think may surprise users when upgrading to
 Clang |release| because of the opportunity they pose for disruption to existing
 code bases.
 
+- Fix a bug in reversed argument for templated operators.
+  This breaks code in C++20 which was previously accepted in C++17. Eg:
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ilya-biryukov wrote:

Could you also clarify add a sentence clarifying that Clang did not properly diagnose this case in C++20 mode before this change?

https://github.com/llvm/llvm-project/pull/72213