#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(maybe_uninit_fill)]
use std::mem::MaybeUninit;
fn main() {
    let mut buf = [const { MaybeUninit::<usize>::uninit() }; 5];
    let initialized = buf.write_with(|idx| idx + 1);
    assert_eq!(initialized, & mut [1, 2, 3, 4, 5]);
}