fn to_usize_array(arr: &[isize]) -> &[usize] {
    let len = arr.len();
    let res = unsafe { std::slice::from_raw_parts(arr.as_ptr() as *const usize, len) };
    &res
}

fn main() {
    assert_eq!(to_usize_array(&[2, 3, 4]), &[2, 3, 4]);
    assert_eq!(
        to_usize_array(&[-4, -5, -6]),
        &[
            18446744073709551612,
            18446744073709551611,
            18446744073709551610
        ],
    );
}