> it already raises a TypeError with a clear message

This is more to my point: I found the TypeError message not clear at all. 

From my prospective, I was using a future object returned from an asyncio function to call another asyncio function, yet that function was telling me it could only use a future with it. 

Though I eventually figured out what was going on, I think that a more clear message at that moment would have been very helpful to me. And I think other users who benefit from this was well.

A better warning/wording for the API would be helpful as well, but I don't think it fully suffices the problem.