Shared via Rust Playground

playground.rs

use std::convert::AsMut;

fn clone_into_array<A, T>(slice: &[T]) -> Option<A>
    where A: Sized + Default + AsMut<[T]>,
          T: Clone
{
    let mut arr = Default::default();
    {
        let mut_arr = <A as AsMut<[T]>>::as_mut(&mut arr);
        let arr_len = mut_arr.len();
        if arr_len > slice.len() {
            return None
        }
        mut_arr.clone_from_slice(&slice[..arr_len]);
    }
    Some(arr)
}

fn main() {
    let a: Option<[u8; 4]> = clone_into_array(&[1, 4, 5, 59, 98]);
    println!("{:?}", a);
}