error_chain.rs

#![feature(conservative_impl_trait)]

extern crate futures;

use futures::future::*;

struct ErrorA;
struct ErrorB;

fn fut_a() -> impl Future<Item = (), Error = ErrorA> {
    ok(())
} 
  
fn fut_b() -> impl Future<Item = (), Error = ErrorB> {
    ok(())
}
    
fn main() {
    let future = fut_a().and_then(|_| fut_b());
}