use std::any::Any;

pub fn dedup_types(list: &mut Vec<Box<Any>>)  {
    list.sort_unstable_by_key(|elem| elem.type_id());
    list.dedup_by_key(|elem| (*elem).type_id());
}

struct Alpha;
struct Beta;
struct Gamma;

pub fn main() {
    let mut list = vec![
        Box::new(Alpha) as Box<Any>,
        Box::new(Gamma) as Box<Any>,
        Box::new(Alpha) as Box<Any>,
        Box::new(Beta) as Box<Any>,
        Box::new(Gamma) as Box<Any>,
        Box::new(Gamma) as Box<Any>,
    ];

    dedup_types(&mut list);
    assert_eq!(list.len(), 3);
}