Bring the Async Rust experience closer to parity with sync Rust

[nikomatsakis]

Metadata
Owner(s)	@tmandry, @nikomatsakis
Team(s)	compiler, lang, libs, libs-api
Goal document	2024h2/async

Summary

Over the next six months, we will deliver several critical async Rust building block features

• resolve the "Send bound" problem, which blocks the widespread usage of async functions in traits;
• reorganize the async WG, so that we can be better aligned and move more swiftly from here out;
• stabilize async closures, allowing for a much wider variety of async related APIs (async closures are implemented on nightly).

Tasks and status

• [ ] Overall program management (@tmandry, @nikomatsakis)
• [ ] "Send bound" problem (@nikomatsakis)
  • [x] Implementation (@compiler-errors)
  • [x] Author RFC (@nikomatsakis)
  • [x] RFC decision: RTN (rust-lang/rfcs#3654) (lang )
  • [ ] RFC decision: Implementable trait aliases (rust-lang/rfcs#3437 or similar)
  • [ ] Stabilization decision (lang )
• [ ] Async WG reorganization (@nikomatsakis)
  • [ ] Author proposal
  • [ ] Org decision (libs, lang )
• [ ] Async closures (@compiler-errors)
  • [x] implementation
  • [x] Author RFC
  • [ ] RFC decision (lang )
  • [ ] Design meeting (lang )
  • [ ] Author call for usage (@compiler-errors)
  • [ ] Stabilization decision (lang )
• [ ] Trait for async iteration (@eholk)
  • [ ] Author RFC
  • [ ] RFC decision (libs-api, lang )
  • [ ] Design meeting (lang )
  • [ ] Implementation
• [ ] Dyn dispatch for AFIT (@spastorino)
  • [ ] Implementation (@spastorino)
  • [ ] Standard reviews (@tmandry)
• [ ] Async drop experiments (@petrochenkov)
  • [x] author MCP
  • [x] MCP decision ()
  • [ ] Implementation work
  • [ ] Design meeting (lang )
  • [ ] Standard reviews (compiler )

[nikomatsakis]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.

[tmandry]

Status update: July 30, 2024

Key developments

• Our project goal was merged :)
• Return type notation RFC was merged (rust-lang/rfcs#3654)
• Async closures RFC is in final comment period (rust-lang/rfcs#3668)

Blockers

We are able to make some progress in each area, but the biggest upcoming blocker we can see is:

• Lang team deciding on final syntax for async closure bounds

Help wanted

There will be a call for testing async closures on the Inside Rust blog soon. Please check it out and give them a try in your own async code!

We'd like to see an updated RFC for implementable trait aliases that follows the guidelines laid out in this comment.