Comment by dminik
I think in practice the caller still needs to know.
If I call `a.foo()` but `a` has and is using a stackless coroutine IO but the caller is being executed from a green thread IO then as was said before, I'm hitting UB.
But, I do like that you could skip/mock IO for instance. That's pretty neat.
here is example code. you wont "use the wrong io".