Lint suggestion: `manual_isolate_lowest_one`

What it does

Checks for manual implementations that returns x with only the least significant bit set, and suggests using x.isolate_lowest_one() instead.

Common manual implementation patterns for this calculation include x & -x or x & x.wrapping_neg(). The - operator is available for signed integer types. The wrapping_neg method is available for both signed and unsigned integer types.

The isolate_lowest_one method will be stabilized in Rust 1.97.0 and will be available for all signed and unsigned primitive integer types and NonZero<T> where T is any signed and unsigned primitive integer type.

Advantage

• Improve readability and clarity compared to manual implementations.
• Eliminate the overflow when x is the smallest value that can be represented by a signed integer type (e.g., i32::MIN) and the - operator is used.
• Preserve non-zero type information by returning NonZero<u32> instead of u32 for NonZero<T>.

x & -x is a well-known trick for finding the least significant bit, but it is opaque to those who don't know this trick.

Drawbacks

Requires MSRV 1.97.0.

Example

let x: u32 = 5;
let lsb = x & x.wrapping_neg();

let x = NonZeroU32::new(5).unwrap();
let lsb = NonZeroU32::new(x.get() & x.get().wrapping_neg()).unwrap();

Could be written as:

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

let x = NonZeroU32::new(5).unwrap();
let lsb = x.isolate_lowest_one();

Comparison with existing lints

No response

Additional Context

No response