use std::collections::HashMap;
use std::sync::{Arc, Weak};

trait MyTrait {}

#[derive(Clone)]
struct MyRef {
    inner: Weak<MyTrait>,
}

impl PartialEq for MyRef {
    fn eq(&self, other: &MyRef) -> bool {
        match (self.inner.upgrade(), other.inner.upgrade()) {
            (Some(ref me), Some(ref it)) => {
                Arc::ptr_eq(me, it)
            }
            _ => false,
        }
    }
}

struct Lookup {
    inner: HashMap<String, MyRef>,
}

impl Lookup {
    fn remove(&mut self, it: MyRef) {
        let matches: Vec<_> = self.inner
            .iter()
            .filter(|&(_, other)| *other == it)
            .map(|(k, _v)| k.clone())
            .collect();
        for m in matches {
            self.inner.remove(&m);
        }
    }
}

fn main() {

}