use std::string::ToString;

trait Foo: ToString {}

struct Bar {}

impl ToString for Bar {
    fn to_string(&self) -> String {
        String::from("Bar")
    }
}

impl Foo for Bar {}

struct Baz {}

impl ToString for Baz {
    fn to_string(&self) -> String {
        String::from("Baz")
    }
}

impl Foo for Baz {}

fn main() {
    let b1: &Foo = &Bar {};
    let b2: &Foo = &Baz {};
    let _v: Vec<&Foo> = vec!(b1, b2);
}