rust-lang/rust-clippy

Lint functions taking references as arguments but only use them to create an owned value

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#1563 opened on Feb 21, 2017

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 (3 comments) (0 reactions) (0 assignees)Rust (10,406 stars) (1,391 forks)batch import
A-lintE-hardL-unnecessaryT-middlegood first issue

Description

A function that takes a &str and always converts it to a String, should be taking a String argument instead. This is hard to generalize, but we could start with anything implementing to_owned and only calling to_owned.

Contributor guide

Tech stack
rust
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Rust knowledgefamiliarity with Clippy lint implementation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
This issue proposes a new lint for Clippy that checks functions taking a reference (like `&str`) but only using it to create an owned value (like `to owned()`). To implement, examine existing lints in the `clippy lints` crate, particularly those in `src/clippy lints/` that deal with function arguments and type checking. Look at the lint 'needless pass by value' as a reference. The current issue lacks a specific implementation strategy; a good starting point is to discuss the lint's scope and possible false positives with maintainers before coding.