#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(downcast_unchecked)]
use std::any::Any;
fn main() {
    let x: Box<dyn Any> = Box::new(1_usize);
    unsafe {
        assert_eq!(* x.downcast_ref_unchecked::< usize > (), 1);
    }
}