rust-lang / rust-lang/rust

rustdoc: support for `async Fn*` trait bounds

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A-async-closures C-bug F-async_trait_bounds requires-nightly T-rustdoc
Dominant language
Rust
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Description

Source:

#![feature(async_closure)]

pub fn demo(_: impl async Fn() -> i32) {}

Current rendered output (local, etc. — more generally: HIR-based) below (issue: dropping the trait bound modifier async).

pub fn demo(_: impl Fn() -> i32)

Current rendered output (inlined cross-crate re-export, etc. — more generally: middle-based) below (issue: leaking the internal desugaring):

pub fn demo(_: impl AsyncFn<(), Output = i32>)

Tracking:

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing rustdoc's HIR-based and middle-based rendering of the async Fn* trait bound shown in the issue. Compare both outputs against the source example; done means the rendered signature preserves the async Fn* bound without dropping async or exposing the internal AsyncFn desugaring.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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