Clippy lint · Performance · checked with Clippy 0.1.99

clippy::manual_contains: using `contains()` instead of `iter().any()` is more efficient

What it meansChecks for usage of iter().any() on slices when it can be replaced with contains() and suggests doing so. It is in the performance group and warns by default.

What you see

warning: using `contains()` instead of `iter().any()` is more efficient
 --> main.rs:4:5
  |
4 |     values.iter().any(|&v| v == 10)
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `values.contains(&10)`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#manual_contains
  = note: `#[warn(clippy::manual_contains)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

contains() is more concise and idiomatic, while also being faster in some cases.

Code that could be written to run faster. Warns by default.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

fn foo(values: &[u8]) -> bool {
    values.iter().any(|&v| v == 10)
}

Write this instead

fn foo(values: &[u8]) -> bool {
    values.contains(&10)
}

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

On one item

#[allow(clippy::manual_contains)]
fn my_function() { /* ... */ }

Whole crate (Cargo.toml)

[lints.clippy]
manual_contains = "allow"

One run

cargo clippy -- -A clippy::manual-contains

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.

Performancegroup

warndefault level

yesfixed by cargo clippy --fix

1.87.0added in Rust

Clippy's own documentation

What it does

Checks for usage of iter().any() on slices when it can be replaced with contains() and suggests doing so.

Why is this bad?

contains() is more concise and idiomatic, while also being faster in some cases.

Example

fn foo(values: &[u8]) -> bool {
    values.iter().any(|&v| v == 10)
}

Use instead:

fn foo(values: &[u8]) -> bool {
    values.contains(&10)
}

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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