gistfile1.txt

extern crate futures;                                                                                                       

use std::str::FromStr;

use futures::{IntoFuture, Future};

fn foo<'a, T: Foo>(string: &'a str) -> Box<Future<Item = T, Error = ()> + 'a> {
    Box::new(string.parse().into_future()
                           .or_else(|_| Err(()))
                           .and_then(|id| Foo::from_id(&id)))
}


pub trait Foo: 'static {
    type Id: FromStr + 'static;
    fn from_id<'a>(&'a Self::Id) -> Box<Future<Item = Self, Error = ()> + 'a>;
}