RS.CLIPPY.NEEDLESS_COLLECT

Collecting an iterator when collect is not needed

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: needless_collect. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for functions collecting an iterator when collect is not needed.

Why is this bad?

collect causes the allocation of a new data structure, when this allocation may not be needed.

Example

let len = iterator.collect::<Vec<_>>().len();

Use instead:

let len = iterator.count();