[clang] #101784 part 1: introduce ctyped in an independent manner (PR #101941)

[Jannick Kremer via cfe-commits]

DeinAlptraum wrote:

@Endilll thanks a lot for the summary! Turning this into documentation also sounds like a good idea.

15\. & 16. fully agree it would be nicer to go without using this `errcheck` functionality, and just call the conversion functions directly. Even if the documentation approves of our use case, imo our current usage is really just abuse of the functionality, and makes the code harder to understand. And as you said, calling it directly would allow us to remove some of the `type: ignore`s.

17\. this does not work out of the box, at least not without further changes. E.g. the exact example you gave there results in an error for me.

https://github.com/llvm/llvm-project/pull/101941