[clang] [Clang] Coroutines: Properly Check if `await_suspend` return type convertible to `std::coroutine_handle<>` (PR #85684)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> > I am confused. If we don't need to check whether a type can be converted to std::coroutine_handle, why do we still need EvaluateBinaryTypeTraits or similar things.
> 
> I thought your previous comment was to show concern about exposing `EvaluateBinaryTypeTraits` contained a bunch of nonfunctional changes.

Yes, this is the intention.

> Do you think it's good?

For the issue we have, it is not. We're introducing a lot of nonfunctional change for a non-standard and unimportant feature... So I may feel better if we can avoid that.


https://github.com/llvm/llvm-project/pull/85684