#![allow(unused_variables)]
fn main() {
    use std::sync::{Arc, Weak};
    let strong = Arc::new("hello".to_owned());
    let raw_1 = Arc::downgrade(&strong).into_raw();
    let raw_2 = Arc::downgrade(&strong).into_raw();
    assert_eq!(2, Arc::weak_count(& strong));
    assert_eq!("hello", &* unsafe { Weak::from_raw(raw_1) } .upgrade().unwrap());
    assert_eq!(1, Arc::weak_count(& strong));
    drop(strong);
    assert!(unsafe { Weak::from_raw(raw_2) } .upgrade().is_none());
}