[clang] [clang] CTAD: Generate deduction guides for alias templates from non-template explicit deduction guides (PR #96686)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 approved this pull request.

One nit, otherwise LGTM.

Regarding the issue of attaching the constraint to a non-template function, pragmatically, this is just something internal to compiler, and we're still conforming to the standard in terms of the user's codes. So, it is probably fine now, given that GCC also seems to take a similar approach here.

However, let's wait another few days before merging if @zygoloid has some insights.

https://github.com/llvm/llvm-project/pull/96686