[Python-Dev] PEP 492: async/await in Python; v3

[Greg]

On 29/04/2015 9:49 a.m., Guido van Rossum wrote:
>     c) 'yield from' only accept coroutine objects from
>     generators decorated with 'types.coroutine'. That means
>     that existing asyncio generator-based coroutines will
>     happily yield from both coroutines and generators.
>     *But* every generator-based coroutine *must* be
>     decorated with `asyncio.coroutine()`.  This is
>     potentially a backwards incompatible change.
>
> See below. I worry about backward compatibility. A lot. Are you saying
> that asycio-based code that doesn't use @coroutine will break in 3.5?

That seems unavoidable if the goal is for 'await' to only
work on generators that are intended to implement coroutines,
and not on generators that are intended to implement
iterators. Because there's no way to tell them apart
without marking them in some way.

-- 
Greg