[clang] [Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer (PR #87933)

[Richard Smith via cfe-commits]

https://github.com/zygoloid approved this pull request.

Looks great!

I think it'd be good to understand what's happening with the static analyzer test, and update the comment to explain. But given that this is fixing a conformance / wrong code bug, I don't think we should block this PR on fixing any issue that turns up in the analyzer, unless it turns out that there's still a conformance issue here.

https://github.com/llvm/llvm-project/pull/87933