rust-lang/rust-clippy

New lint: clone on arguments taken by reference

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#2,074 opened on Sep 19, 2017

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A-lintL-unnecessaryT-middlegood first issue

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Description

If a function takes an argument by reference, but later calls .clone() on it (or otherwise requires an impl Clone or impl Copy from it), lint that taking it by ownership allows the caller to pass in its memory rather than forcing a clone on the data.

I don't know if this is possible, but can it default to allow on public functions and deny on crate-private functions (due to the API change)?

Contributor guide

Research direction
Study the Clippy lint creation guide. Implement a new lint that detects when a function argument is taken by reference but later cloned, indicating it should be taken by value. Consider the allow/deny defaults based on visibility.
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
Rust
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70