ref_mut_n_lines

This defines a nested mutable reference.

use ref_mut_n_lines::ref_mut_n_lines;

fn main() {
    let mut data = [[0u8; 3]; 4];
    let _ref_data: &mut [&mut [u8]] = ref_mut_n_lines!(data, 4);
}

work as

let _ref_data: &mut [&mut [u8]] = {
    let [ref mut a0, ref mut a1, ref mut a2, ref mut a3] = data;
    &mut[a0, a1, a2, a3]
}