Lint suggestion: `manual_isolate_highest_one`

What it does

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

The isolate_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 off-by-one errors for $x = 0$.
• Preserve non-zero type information by returning NonZero<u32> instead of u32 for NonZero<T>.

Drawbacks

Requires MSRV 1.97.0.

Example

let x: u32 = 5;
// `31 == (u32::BITS - 1)`
let msb = x & ((1_u32 << 31).wrapping_shr(x.leading_zeros()));
let msb = if x == 0 {
    0
} else {
    1 << (31 - x.leading_zeros())
};

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

Could be written as:

let x: u32 = 5;
let msb = x.isolate_highest_one();

let x = NonZeroU32::new(5).unwrap();
let msb = x.isolate_highest_one();

Comparison with existing lints

No response

Additional Context

No response

Start by locating existing Clippy lint implementations for analogous bit-operation suggestions and their tests. Use the issue's examples to cover manual highest-bit isolation for signed and unsigned primitives and NonZero types, gated by MSRV 1.97.0; done means the lint suggests isolate_highest_one without off-by-one behavior for x = 0.