Reconsider `Context::executor` returning `Option`

[carllerche]

It seems that Context::executor was changed to return Option because in no_std Executor is not available.

However, the executor fn is not included when no_std is enabled. Given that Context::executor is present so that all callers can assume that an executor is present, would it be better for it not to return an Option?

Maybe if std is present, initializing a Context w/o a can panic?

[aturon]

Yeah, I think this was a design mistake. I now have a design in mind that is no_std compatible and allows everyone to use executors, but I want to punt it to 0.3 (so we can go ahead and get 0.2 out the door). RFC coming soon.

[carllerche]

What is the timeline to 0.3?

Is the plan that 0.3 will include a breaking change for futures-core?