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

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> In SemaExprCXX.cpp there's EvaluateBinaryTypeTraits that I needed to expose as suggested by the comment in SemaCoroutine. Is there an alternative way to do type coercion/equivalence checks?

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.

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