Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::explicit_counter_loop: Checks for loops over slices with an explicit counter and suggests the use of .enumerate()

What it meansChecks for loops over slices with an explicit counter and suggests the use of .enumerate(). It is in the complexity group and warns by default.

Does it matter?

Using .enumerate() makes the intent more clear, declutters the code and may be faster in some instances.

Code that does something simple in a complicated way. Warns by default.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

let mut i = 0;
for item in &v {
    bar(i, *item);
    i += 1;
}

Write this instead

for (i, item) in v.iter().enumerate() { bar(i, *item); }

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
explicit_counter_loop = "allow"

One run

cargo clippy -- -A clippy::explicit-counter-loop

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.

Complexitygroup

warndefault level

nofixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for loops over slices with an explicit counter and suggests the use of .enumerate().

Why is this bad?

Using .enumerate() makes the intent more clear, declutters the code and may be faster in some instances.

Example

let mut i = 0;
for item in &v {
    bar(i, *item);
    i += 1;
}

Use instead:

for (i, item) in v.iter().enumerate() { bar(i, *item); }

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

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