#![allow(unused_variables)]
#![feature(binary_heap_peek_mut_refresh)]
fn main() {
    use std::collections::BinaryHeap;
    let mut heap: BinaryHeap<u32> = [1, 2, 3].into();
    let mut peek = heap.peek_mut().unwrap();
    assert_eq!(* peek, 3);
    *peek = 42;
    assert!(! peek.refresh(), "42 is even larger than 3");
    assert_eq!(* peek, 42);
}