[clang] [Clang] Don't give up on an unsuccessful function instantiation (PR #126723)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov commented:

Sorry that took a while, I am still coming back from WG21, so I can't look into this throughly yet.

I would look into / want to know about the very specific requirements on hitting the bug, described in the bug report, such as the lambda vs struct thing.

https://github.com/llvm/llvm-project/pull/126723