Lint suggestion: `manual_highest_one`

What it does

Checks for manual implementations that returns the index of the highest bit set to one in x, and suggests using x.highest_one() instead.

The highest_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 zero.

Drawbacks

Requires MSRV 1.97.0.

Example

let x: u32 = 5;
// `31 == (u32::BITS - 1)`
let index = 31 - x.leading_zeros();
let index = if x == 0 {
    None
} else {
    Some(31 - x.leading_zeros())
};

let x = NonZeroU32::new(5).unwrap();
// `31 == (NonZeroU32::BITS - 1)`
let index = 31 - x.leading_zeros();

Could be written as:

let x: u32 = 5;
let index = x.highest_one().unwrap();
let index = x.highest_one();

let x = NonZeroU32::new(5).unwrap();
let index = x.highest_one();

Comparison with existing lints

No response

Additional Context

No response