rust-lang / rust-lang/rust-clippy

new lint: reflexive String queries: s.find(&s)

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A-lint
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Rust
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Description

This was inspired by a cppcheck lint.
operations like s.find(&s); on strings will always yield the same results so they are probably not intentional.

fn main() {
    let s = String::from("hello world");
    let a = s.find(&s); // always 0
    let b = s.ends_with(&s); // always true
    let c = s.contains(&s); // always true
    let d = s.starts_with(&s); // always true
}

currently, none of these trigger a related warning.

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Research direction

The issue names no implementation file or test. Start by locating Clippy’s existing String-method lints and their UI tests, then verify the four self-query examples produce diagnostics without false positives; done means the new lint is registered and its expected warnings pass.

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
35/100

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