#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(once_cell_try_insert)]
use std::cell::OnceCell;
fn main() {
    let cell = OnceCell::new();
    assert!(cell.get().is_none());
    assert_eq!(cell.try_insert(92), Ok(& 92));
    assert_eq!(cell.try_insert(62), Err((& 92, 62)));
    assert!(cell.get().is_some());
}