#![allow(unused_variables)]
fn main() {
    use std::sync::{Arc, Weak};
    struct Foo;
    impl Drop for Foo {
        fn drop(&mut self) {
            println!("dropped!");
        }
    }
    let foo = Arc::new(Foo);
    let weak_foo = Arc::downgrade(&foo);
    let other_weak_foo = Weak::clone(&weak_foo);
    drop(weak_foo);
    drop(foo);
    assert!(other_weak_foo.upgrade().is_none());
}