[clang] [Clang] Correctly propagate type aliases' unexpanded flags up to lambda (PR #122875)

[Matheus Izvekov via cfe-commits]

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

I think the change is ok, but I don't think this fixes the underlying issue. There is something generally wrong with type aliases which don't use all of their parameters, and this needs more thought.

https://github.com/llvm/llvm-project/pull/122875