Async project goal

[nikomatsakis]

This is a proposed flagship goal for 2024h2 covering async Rust. You can read more about the project goal slate and its associated process here. This RFC is prepared using the project goal template, which differs from the typical RFC template.

The overall goal is bringing the Async Rust experience closer to parity with sync Rust. We have identified three high-priority goals that we believe would do the most to improve async over the long term:

• resolving the "send bound problem", thus enabling foundational, generic traits like Tower's Service trait;
• stabilizing async closures, thus enabling richer, combinator APIs like sync Rust's Iterator;
• reorganizing the async WG, so the project can benefit from a group of async rust experts with deep knowledge of the space that can align around a shared vision;

We have also identified two "stretch goals":

• stabilizing a trait in libstd for async iteration, thus enabling the ecosystem to build atop a stable foundation;
• completing the async drop experiments proposed in MCP 727, laying the groundwork for resolving the the next major gap in language feature support.

Approving this goal implies agreement from the Lang, Libs, and Libs-API teams to the items marked as in the table of work items, along with potentially other design meetings as needed.

Rendered

[nikomatsakis]

@rfcbot fcp merge

This project goal has been under development and discussion for some time. Since discussion on the thread has been relatively quiet, I'm going to go ahead and propose to merge it now. There will be a long list of checkboxes regardless so I want to get that discussion up and going.

[rfcbot]

Team member @nikomatsakis has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se
• @nikomatsakis
• @pnkfelix
• @scottmcm
• @tmandry

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

[nikomatsakis]

Thanks for the edits. Will respond now to the more thoughtful questions.

[nikomatsakis]

After discussion with @tmandry I have made two major updates to the goal structure

• First, we removed the async vision doc, which seemed a bit premature and overly ambitious. We have replaced it with the goal to reorganize the async WG.
• Second, I added more explicit prioritization, clarifying the async iteration + async drop are "stretch goals". The prioritization is based on what will set us up for long-term success.

[nikomatsakis]

Upon reflection, I've decided to change the process for approving project goals. I'm going to close this RFC, but the content is still correct.

[bew]

Hello, I was following this rfc (was probably mentioned in TWiR), is there a new/different issue/object to follow? 🤔

[clarfonthey]

I shared a similar question on the other RFC that was closed relating to project goals; might be worth centralising the discussion there: #3658 (comment)

Although presumably an alternative link to follow this specific goal will be provided here once that discussion has finished.