[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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@@ -120,10 +120,11 @@ void aggregateWithReferences() {
   clang_analyzer_dump(viaReference);    // expected-warning-re {{&lifetime_extended_object{RefAggregate, viaReference, S{{[0-9]+}}} }}
   clang_analyzer_dump(viaReference.rx); // expected-warning-re {{&lifetime_extended_object{int, viaReference, S{{[0-9]+}}} }}
   clang_analyzer_dump(viaReference.ry); // expected-warning-re {{&lifetime_extended_object{Composite, viaReference, S{{[0-9]+}}} }}
-
-  // clang does not currently implement extending lifetime of object bound to reference members of aggregates,
-  // that are created from default member initializer (see `warn_unsupported_lifetime_extension` from `-Wdangling`)
-  RefAggregate defaultInitExtended{i}; // clang-bug does not extend `Composite`
+  
+  // FIXME: clang currently support extending lifetime of object bound to reference members of aggregates,
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erichkeane wrote:

Please create an issue for this if it doesn't exist.

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