[clang] Fix enum enumerator visibility loss when #include is between module imports (PR #188865)

[Avi Kivity via cfe-commits]

avikivity wrote:

> > I could feed your feedback to the AI, but then I just become a conduit between you. I don't mind doing that but I don't think it's effective. I just don't have sufficient understanding of the codebase.
> 
> @avikivity this depends on what you want to do,
> 
> if you just want to provide a issue report and some hints to compiler developers, I think you've done a great job. It indeed helped me to understand the problem sooner.
> 
> But if you want to contribute the project directly, according to our AI policy (https://llvm.org/docs/AIToolPolicy.html), you have to understand what you send.

I cannot claim to have a deep understanding, or even shallow, of the changes. They are too complicated for me to follow without a deep study of the code.

If the AI generated changes are not helpful, I'll close this pull request. In my opinion, they are useful at least as a hint of what a change would look like.

btw, I encountered two more issues related to module support, and AI successfully solved them (although, perhaps not in an acceptable way). I planned to file them once we made progress here, I can file them earlier, with or without the proposed fix, whichever you prefer.

https://github.com/llvm/llvm-project/pull/188865