Recognize trailing_ones code patterns

What it does

Perhaps Clippy could spot code patterns like foo2() and suggest to replace that loop with trailing_ones() (and similar code for the other functions like trailing_zeros and leading_zeros):

fn foo1(x: usize) -> u32 {
    x.trailing_ones()
}

fn foo2(mut x: usize) -> u32 {
    let mut count = 0;
    while x & 1 == 1 {
        x >>= 1;
        count += 1;
    }
    count
}

fn main() {
    for i in 0 .. 1_000 {
        assert_eq!(foo1(i), foo2(i));
    }
}

In Rust code translated from C and C++ code I see many of such small loops (GCC has many functions like __builtin_clz(), but they are less portable so lot of people don't use them or don't remember to use them).

Lint Name

No response

Category

No response

Advantage

No response

Drawbacks

No response

Example

<code>

Could be written as:

<code>

Start with the Rust examples in the issue, especially the foo2 loop, and inspect how rust-clippy implements and tests similar pattern-recognition lints. The work is complete when equivalent loops are recognized and suggestions use trailing_ones(), trailing_zeros(), and leading_zeros() appropriately, with coverage for the shown behavior.