use std::fmt::{self,Display,Formatter};
use std::string::ToString;

struct Foo<T>(pub Option<T>);

impl<T: Display> Display for Foo<T> {
    fn fmt(&self, _f: &mut Formatter) -> fmt::Result {
        Ok(())
    }
}

struct Bar { bar: usize }

impl Display for Bar {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        f.write_str("bar")
    }
}

fn main() {
   let to_string = ToString::to_string;
   let i = Bar { bar: 1 };
   let foo = Foo(Some(&i));
   assert_eq!("bar", to_string(&foo));
}