#![feature(nll)]

use std::collections::HashMap;

fn get_default(map: &mut HashMap<usize, String>, key: usize) -> &mut String {
    match map.get_mut(&key) {
        Some(value) => value,
        None => {
            map.insert(key, "".to_string());
            map.get_mut(&key).unwrap()
        }
    }
}

fn main() {
    let map = &mut HashMap::new();
    map.insert(22, format!("Hello, world"));
    map.insert(44, format!("Goodbye, world"));
    assert_eq!(&*get_default(map, 22), "Hello, world");
    assert_eq!(&*get_default(map, 66), "");
}