[llvm] [LLVM Demangler] Set `InConstraintExpr` to `true` when demangling a c… (PR #107385)

[Ilya Biryukov via llvm-commits]

https://github.com/ilya-biryukov requested changes to this pull request.

My main request is to add a test for the cases that used to fail. Otherwise LG, and I hope this is temporary and we would follow up with addressing the actual underlying problem.

Also, see a few suggestions on naming and wording.

Suggestion: a much more common tag for the commit title is `[Demangle]` or `[ItaniumDemangle]`. Could we use one of those two for consistency?

Could you also mention #89914 in the commit message so that people can access the relevant discussions right away?

https://github.com/llvm/llvm-project/pull/107385