Cython functions that return a generator aren't special in any way, so it's actually correct that isgeneratorfunction() always returns False. I mean, I could set the CO_COROUTINE flag on the code object that we fake, but that wouldn't help much as Cython's functions are not Python functions, so isfunction() will also return False for them and no-one would look at the flag in the first place. And finally, a Cython generator is not a Python generator (with byte code position etc.), so isgenerator() also correctly returns False.

At least iscoroutine() and iswaitable() will return True for Cython Coroutines now.