rust-lang / rust-lang/rust-clippy

lint impl on trait object

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A-lint E-medium T-middle
Dominant language
Rust
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Description

Example code:

trait Foo {}

impl Foo {
    fn bar(&self) {
        /* whatever */
    }
}

The lint would be "warning: this adds a method to a trait object type, which is rarely intended. Consider a blanket impl of Foo instead."

Advanced mode: rewrite the impl header to suggest impl<T> Foo for T.

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 reproducing the Rust example from the issue in Clippy and inspect how existing lints detect inherent implementations on trait objects. Done means emitting the proposed warning for this pattern and, if the advanced mode is supported, suggesting a blanket impl such as impl Foo for T; add coverage for both behaviors.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
38/100

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