clippy::manual_isolate_lowest_one: manual implementation of `isolate_lowest_one`

What you see

warning: manual implementation of `isolate_lowest_one`
 --> main.rs:4:11
  |
4 | let lsb = x & x.wrapping_neg();
  |           ^^^^^^^^^^^^^^^^^^^^ help: consider using `.isolate_lowest_one()`: `x.isolate_lowest_one()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#manual_isolate_lowest_one
  = note: `#[warn(clippy::manual_isolate_lowest_one)]` 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?

The manual bit-twiddling forms are harder to read than the standard library method. Using -x can also overflow for signed minimum values.

Code that does something simple in a complicated way. 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: u32 = 5;
let lsb = x & x.wrapping_neg();

Write this instead

let x: u32 = 5;
let lsb = x.isolate_lowest_one();

Turn it off, or on

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

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

[lints.clippy]
manual_isolate_lowest_one = "allow"

cargo clippy -- -A clippy::manual-isolate-lowest-one

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.

Settings in clippy.toml

• msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml