Async fundamentals initiative

[tmandry]

Proposal

Summary and problem statement

async fn exists today, but does not integrate well with many core language features like traits, closures, and destructors. We would like to make it so that you can write async code just like any other Rust code.

Motivation, use-cases, and solution sketches

• Able to write async fn in traits and impls
  • Return futures can easily be bound by Send
  • Traits that use async fn can still be dyn safe
• Able to write destructors that await (async drop)
• Support for async closures

Links and related work

This initiative already has a website and Github repo with design notes.

Initial people involved

• Owner: @tmandry
• Liaison: @nikomatsakis

What happens now?

This issue is part of the lang-team initiative process. Once this issue is filed, a Zulip topic will be opened for discussion, and the lang-team will review open proposals in its weekly triage meetings. You should receive feedback within a week or two.

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[rustbot]

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[nikomatsakis]

@tmandry I think we should close this and re-open with a clearer deliverable -- async fns in traits.

[nikomatsakis]

Going to go ahead and do that