rust-lang/rust-clippy

Lint for Iterator + Copy

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#1,534 opened on Feb 13, 2017

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A-lintE-mediumL-correctnessgood first issue

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Description

Implementing Copy for iterators makes footguns, and the standard library settled not to do so for now.

let mut it = /* a Copy + Iterator */;
for x in it { if cond { break; } } // `it` copied here (forgot to `&mut it`)
let x = it.next(); // `it` is in the initial state

Clippy should have a lint that warns if "use of the original iterator after copied" is detected.

Contributor guide

Research direction
Study existing Clippy lints that detect iterator misuse (e.g., 'iter not returning iterator'). Understand how Clippy tracks state across statements. Write a new lint that warns when a Copy iterator is used after a for loop that may have consumed it.
Tech stack
rust
Domain
developer experience
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.
Half day
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.
Clear
Prerequisites
Rust
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40