Comment by zelphirkalt

Function coloring is the issue, that arises in practice, which is why people discuss, whether some approach solves it or does not.

Why do you think it automatically follows, that with an async I/O you are going to have a streaming API? An async I/O can just like the sync I/O return a whole complete result, only that you are not waiting for that to happen, but the called async procedure will call you back once the result is calculated. I think a streaming API requires additional implementation effort, not merely async.