Draft RFC to add Stream to the standard library

[nikomatsakis]

No description provided.

[nikomatsakis]

Something else I was wondering: where in the standard library hierarchy should this trait live? I have to check what @sfackler did in the PR I guess.

More generally I feel like we have to decide whether to just sprinkle async things here and there with names like AsyncFoo or to take some other approach (e.g., std::async::..., although that's a keyword). I guess maybe it depends on how many additions we ultimately have.

[yoshuawuyts]

I guess maybe it depends on how many additions we ultimately have.

async-std is effectively a big experiment to see how much of the stdlib would be useful (and possible) to port to async Rust. And so far the it seems virtually everything async-std provides is seeing use by people. What this means for the stdlib is that it would be reasonable to leave ourselves with enough space to grow, even if we're currently only considering a modest set of APIs for inclusion. Examples of "We may want to include a lot of this in the future" are: the io submodule (37 top-level exports) and sync submodule (18 top-level exports).

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where in the standard library hierarchy should this trait live?

That's a really good question. @sfackler added it under core::stream, which makes sense as a counterpart to core::future. But when we consider AsyncRead and AsyncWrite for inclusion there may be different tradeoffs and the obvious std::io submodule may not be the best fit.

[yoshuawuyts]

So far this reads really well. Added a few notes of things that seem worth of mention. Very excited for this!

[nikomatsakis]

I'm going to merge this as a WIP -- we'll need to do follow-up work to flesh it out.