#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let x = &mut [0, 1, 2];
    if let Some(first) = x.first_chunk_mut::<2>() {
        first[0] = 5;
        first[1] = 4;
    }
    assert_eq!(x, & [5, 4, 2]);
    assert_eq!(None, x.first_chunk_mut::< 4 > ());
}