Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::map_clone: you are using an explicit closure for copying elements
What it meansChecks for usage of map(|x| x.clone()) or dereferencing closures for Copy types, on Iterator or Option, and suggests cloned() or copied() instead It is in the style group and warns by default.
What you see
warning: you are using an explicit closure for copying elements --> main.rs:5:9 | 5 | let z = y.map(|i| *i); | ^^^^^^^^^^^^^ help: consider calling the dedicated `copied` method: `y.copied()` | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#map_clone = note: `#[warn(clippy::map_clone)]` 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?
Readability, this can be written more concisely
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 x = vec![42, 43];
let y = x.iter();
let z = y.map(|i| *i);
Write this instead
let x = vec![42, 43];
let y = x.iter();
let z = y.cloned();
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::map_clone)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
map_clone = "allow"One run
cargo clippy -- -A clippy::map-cloneThe [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.
Settings in clippy.toml
msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml
Clippy's own documentation
What it does
Checks for usage of map(|x| x.clone()) or
dereferencing closures for Copy types, on Iterator or Option,
and suggests cloned() or copied() instead
Why is this bad?
Readability, this can be written more concisely
Example
let x = vec![42, 43];
let y = x.iter();
let z = y.map(|i| *i);
The correct use would be:
let x = vec![42, 43];
let y = x.iter();
let z = y.cloned();
Configuration
-
msrv: The minimum rust version that the project supports. Defaults to therust-versionfield inCargo.toml(default:
current version)
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- needless_returnunneeded `return` statement
- 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
- manual_saturating_arithmeticChecks for .checked_add/sub(x).unwrap_or(MAX/MIN)
- manual_slice_fillmanually filling a slice
- manual_while_let_someyou seem to be trying to pop elements from a `Vec` in a loop
- map_collect_result_unit`.map().collect()` can be replaced with `.try_for_each()`
- match_like_matches_macromatch expression looks like `matches!` macro
- match_overlapping_armsome ranges overlap
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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