[clang] Reapply "[Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer" (PR #108039)

[Erich Keane via cfe-commits]

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@@ -2509,8 +2509,9 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
 
       // P2718R0 - Lifetime extension in range-based for loops.
       if (getLangOpts().CPlusPlus23) {
-        auto &LastRecord = Actions.ExprEvalContexts.back();
+        auto &LastRecord = Actions.currentEvaluationContext();
         LastRecord.InLifetimeExtendingContext = true;
+        LastRecord.RebuildDefaultArgOrDefaultInit = true;
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erichkeane wrote:

Why is this in C++23 only?  I would expect this to apply to older stuff as well, particularly since this is a DR, right?

https://github.com/llvm/llvm-project/pull/108039