rust-lang / rust-lang/rust-clippy
Lint needless `&mut` when `&` suffices
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A-lint
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- Rust
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Description
Idea: Add a lint for unneeded mutable borrows when an immutable borrow suffices:
fn main() {
let m = &mut 21; // `&21` would suffice
println!("{}", m);
}
This lint could also catch an unneeded ref mut when a plain ref suffices:
fn main() {
let test = &mut Test{a: 1};
let &mut Test{ ref mut a } = test;
println!("{}", a);
}
struct Test {
a: i32,
}
cc @oli-obk
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start from the two Rust examples in the issue and determine the cases where mutable borrows or ref mut are unnecessary. Define the lint's scope and verify that it reports only cases where immutable borrowing suffices, with tests covering both examples.
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
- Mostly clear
- Newbie friendliness
- 30/100