clippy::collection_is_never_read: Checks for collections that are never queried

Does it matter?

Putting effort into constructing a collection but then never querying it might indicate that the author forgot to do whatever they intended to do with the collection. Example: Clone a vector, sort it for iteration, but then mistakenly iterate the original vector instead.

New lints still being finished. Off by default and may have false positives.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

let mut sorted_samples = samples.clone();
sorted_samples.sort();
for sample in &samples { // Oops, meant to use `sorted_samples`.
    println!("{sample}");
}

Write this instead

let mut sorted_samples = samples.clone();
sorted_samples.sort();
for sample in &sorted_samples {
    println!("{sample}");
}

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

[lints.clippy]
collection_is_never_read = "warn"

#![warn(clippy::collection_is_never_read)]

cargo clippy -- -W clippy::collection-is-never-read

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.