[clang] [Clang][Parser] Accept P2741R3 (static_assert with user-generated message) in C++11 as an extension (PR #102044)

[Vlad Serebrennikov via cfe-commits]

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@@ -671,10 +671,8 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
                         LangOpts.CPlusPlus23   ? "202211L"
                         : LangOpts.CPlusPlus17 ? "201603L"
                                                : "200907");
-    Builder.defineMacro("__cpp_static_assert", LangOpts.CPlusPlus26 ? "202306L"
-                                               : LangOpts.CPlusPlus17
-                                                   ? "201411L"
-                                                   : "200410");
+    // C++17 / C++26 static_assert backported
+    Builder.defineMacro("__cpp_static_assert", "202306L");
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Endilll wrote:

Looking at how we handle other backported features, it appears that we didn't change anything about feature test macros when we enabled them. In other words, what was undefined remain undefined, what was defined is still defined to have the same value as if backport never happened.

https://github.com/llvm/llvm-project/pull/102044