Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::unused_enumerate_index: you seem to use `.enumerate()` and immediately discard the index
What it meansChecks for uses of the enumerate method where the index is unused (_) It is in the style group and warns by default.
What you see
warning: you seem to use `.enumerate()` and immediately discard the index --> main.rs:4:23 | 4 | for (_, x) in v.iter().enumerate() { | ^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unused_enumerate_index = note: `#[warn(clippy::unused_enumerate_index)]` on by default help: remove the `.enumerate()` call | 4 - for (_, x) in v.iter().enumerate() { 4 + for x in v.iter() { |
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?
The index from .enumerate() is immediately dropped.
Code that works but is not idiomatic Rust. 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
let v = vec![1, 2, 3, 4];
for (_, x) in v.iter().enumerate() {
println!("{x}");
}
Write this instead
let v = vec![1, 2, 3, 4];
for x in v.iter() {
println!("{x}");
}
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::unused_enumerate_index)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
unused_enumerate_index = "allow"One run
cargo clippy -- -A clippy::unused-enumerate-indexThe [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.
Clippy's own documentation
What it does
Checks for uses of the enumerate method where the index is unused (_)
Why is this bad?
The index from .enumerate() is immediately dropped.
Example
let v = vec![1, 2, 3, 4];
for (_, x) in v.iter().enumerate() {
println!("{x}");
}
Use instead:
let v = vec![1, 2, 3, 4];
for x in v.iter() {
println!("{x}");
}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
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- new_without_defaultChecks for public types with a pub fn new() -> Self method and no implementation of Default
- len_zeroChecks for getting the length of something via .len() just to compare to zero, and suggests using .is_empty() where applicable
- unnecessary_owned_empty_stringsusage of `&String::new()` for a function expecting a `&str` argument
- unneeded_struct_patternstruct pattern is not needed for a unit variant
- unsafe_removed_from_nameChecks for imports that remove “unsafe” from an item’s name
- unused_unitunneeded unit expression
- unusual_byte_groupingsWarns if hexadecimal or binary literals are not grouped by nibble or byte
- unwrap_or_defaultChecks for usages of the following functions with an argument that constructs a default value (e.g., Default::default or String::new): unwrap_or unwrap_or_else or_insert or_insert_with
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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