iter-overeager-cloned

Delay iterator cloning until after operations that discard elements

Cloning iterator values before filtering or selection may clone values that the operation discards.
Instead, you SHOULD apply cloned after filtering or limiting adapters and clone only values returned by terminal selectors.

- Category: performance
- Level: warning
- Fix: suggestion
- Scope: module

Reported

import { Iterator } from "destack:iter";

struct Label {
    values: ^int32[];
}

function prefix(values: Iterator<&readonly Label>, count: isize): Iterator<Label> {
    return values.cloned().take(count);
}
Accepted

import { Iterator } from "destack:iter";

struct Label {
    values: ^int32[];
}

function prefix(values: Iterator<&readonly Label>, count: isize): Iterator<Label> {
    return values.take(count).cloned();
}
Prior art

- Clippy · iterovereagercloned

language/linter/src/rules/performance/iterovereagercloned.rs:12