Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::manual_rotate: there is no need to manually implement bit rotation
What it meansIt detects manual bit rotations that could be rewritten using standard functions rotate_left or rotate_right. It is in the style group and warns by default.
What you see
warning: there is no need to manually implement bit rotation --> main.rs:4:9 | 4 | let _ = (x >> 8) | (x << 24); | ^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x.rotate_right(8)` | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#manual_rotate = note: `#[warn(clippy::manual_rotate)]` 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?
Calling the function better conveys the intent.
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 = 12345678_u32;
let _ = (x >> 8) | (x << 24);
Write this instead
let x = 12345678_u32;
let _ = x.rotate_right(8);
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_rotate)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
manual_rotate = "allow"One run
cargo clippy -- -A clippy::manual-rotateThe [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
It detects manual bit rotations that could be rewritten using standard
functions rotate_left or rotate_right.
Why is this bad?
Calling the function better conveys the intent.
Known issues
Currently, the lint only catches shifts by constant amount.
Example
let x = 12345678_u32;
let _ = (x >> 8) | (x << 24);
Use instead:
let x = 12345678_u32;
let _ = x.rotate_right(8);
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_pattern_char_comparisonthis manual char comparison can be written more succinctly
- manual_range_containsmanual `Range::contains` implementation
- manual_repeat_nthis `repeat().take()` can be written more concisely
- 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
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?