Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::neg_multiply: Checks for multiplication by -1 as a form of negation
What it meansChecks for multiplication by -1 as a form of negation. It is in the style group and warns by default.
Does it matter?
It’s more readable to just negate.
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 a = x * -1;
Write this instead
let a = -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::neg_multiply)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
neg_multiply = "allow"One run
cargo clippy -- -A clippy::neg-multiplyThe [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 multiplication by -1 as a form of negation.
Why is this bad?
It’s more readable to just negate.
Example
let a = x * -1;
Use instead:
let a = -x;
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
- needless_range_loopthe loop variable `i` is only used to index `vec`
- needless_return_with_question_markChecks for return statements on Err paired with the ? operator
- new_ret_no_selfChecks for new not returning a type that contains Self
- non_minimal_cfgunneeded sub `cfg` when there is only one condition
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::needless_returnunneeded `return` statementRead it next →Did this answer your question?