more details

gistfile1.txt

fn sometestbox(
    c: future::Loop<u32, u32>,
) -> Box<Future<Item = future::Loop<u32, u32>, Error = u32> + Send> {
    if let future::Loop::Continue(i) = c {
        let delay = Instant::now().add(Duration::from_secs(1));

        Box::new(
            Delay::new(delay)
                .map(move |_| future::Loop::Continue(i))
                .map_err(|_| 1)
        )
    } else {
        Box::new(future::ok(c))
    }
}


//this one does not compile
//giving the error:
// `if let` arms have incompatible types
//expected struct `futures::MapErr`, found struct `futures::FutureResult`
//note: expected type `futures::MapErr<futures::Map<tokio::timer::Delay, [closure@src/bin/main.rs:84:18: 84:52 i:_]>, [closure@src/bin/main.rs:85:22: 85:27]>`
//        found type `futures::FutureResult<futures::future::Loop<u32, u32>, _>`
fn sometest(
    c: future::Loop<u32, u32>,
) -> impl Future<Item = future::Loop<u32, u32>, Error = u32>  {
    if let future::Loop::Continue(i) = c {
        let delay = Instant::now().add(Duration::from_secs(1));

        Delay::new(delay)
            .map(move |_| future::Loop::Continue(i))
            .map_err(|_| 1)
        
    } else {
        future::ok(c)
    }
}