[clang] [Clang] SubstituteConstraintExpressionWithoutSatisfaction needs an unevaluated context (PR #123883)

[Younan Zhang via cfe-commits]

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@@ -248,6 +248,25 @@ ExprResult Parser::ParseArrayBoundExpression() {
   // If we parse the bound of a VLA... we parse a non-constant
   // constant-expression!
   Actions.ExprEvalContexts.back().InConditionallyConstantEvaluateContext = true;
+  // For a VLA type inside an unevaluated operator like:
+  //
+  //   sizeof(typeof(*(int (*)[N])array))
+  //
+  // in which the expression N is supposed to be ODR-used, as is the `array`.
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zyn0217 wrote:

It's already there: https://github.com/llvm/llvm-project/blob/ebb27ccb08e0579825a53b218ff5b2ddc492626a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp#L225-L248

https://github.com/llvm/llvm-project/pull/123883