rust-lang / rust-lang/rust-analyzer

feature request: inlay hints for default trait object lifetimes

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A-inlay-hints C-feature
Dominant language
Rust
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Description

I recently found out about this (very cool!) feature of r-a to show elided lifetimes of functions as inlay hints and thought it would be even cooler it could also show the default trait object lifetimes, because they can often be confusing.

For example this input

trait Trait {}
fn foo(_: &dyn Trait, _: Box<dyn Trait>) {}

could be displayed as

trait Trait {}
fn foo<'0>(_: &'0 (dyn Trait + '0), _: Box<dyn Trait + 'static>) {}

to explicitly show the inferred lifetime of trait objects.

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

No file, test, or entry point is named. Start by locating the existing inlay-hint implementation for elided function lifetimes, then trace how it represents inferred lifetimes; done means default trait-object lifetimes are shown as in the issue's reference-bound and 'static examples.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
developer-experience, tooling
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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