#![feature(conservative_impl_trait)]

extern crate futures;
extern crate tokio_core;
use futures::future::{self};
use futures::future::*;
use tokio_core::reactor::Core;

fn main() {
    let mut core = Core::new().expect("Failed to initialize tokio_core reactor!");

    let f = test();

    core.run(f).unwrap();
}

fn test() -> MapErr<(), ()> {
    future::ok(())
        .map_err(|String| ())
}