The promises winrt::fire_and_forget and winrt::impl::promise_base have the member function await_transform which uses winrt::impl::notify_awaiter, which uses winrt::impl::get_awaiter, which in turn uses winrt::impl::awaiter_finder.

When you do things like co_await 10ms in a coroutine with one of these promise types, the await_transform member function is called, and the operator co_await for std::chrono::duration is resolved by winrt::impl::get_awaiter using winrt::impl::awaiter_finder.

This works in MSVC, however Clang and GCC don't like it when the operator co_await is not declared before the definition of the awaiter_finder template class: https://godbolt.org/z/hbhhMdj3d

I believe this is the reason why some of the tests using co_await does not work on Clang without these workarounds in #1203.

Any ideas? I cannot tell which compilers are doing it wrong.