reqchan 0.5.8

This is a channel for requesting and receiving data. Each channel has only one requesting end, but it can have multiple responding ends. It is useful for implementing work sharing. The two ends of the channel are asynchronous with respect to each other, so it is kinda nonblocking. However, if multiple responding ends try to respond to the same request, only one will succeed; the rest will return errors.
Documentation 
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use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread;

extern crate reqchan;
use reqchan::*;

trait FnBox {
    fn call_box(self: Box<Self>);
}

impl<F: FnOnce()> FnBox for F {
    fn call_box(self: Box<F>) {
        (*self)()
    }
}

type Task = Box<FnBox + Send + 'static>;

#[test]
fn test_request_receive_threaded() {
    let (rqst, resp) = channel::<Task>();

    let var = Arc::new(AtomicUsize::new(0));
    let var2 = var.clone();

    let handle = thread::spawn(move || {
        loop {
            match resp.try_respond() {
                Ok(contract) => {
                    contract.send(Box::new(move || {
                        var2.fetch_add(1, Ordering::SeqCst);
                    }) as Task);
                    break;
                },
                Err(TryRespondError::NoRequest) => {},
                Err(TryRespondError::Locked) => { assert!(false); },
            }
        }
    });

    let mut contract = rqst.try_request().unwrap();

    loop {
        match contract.try_receive() {
            Ok(task) => {
                task.call_box();
                break;
            },
            Err(TryReceiveError::Empty) => {},
            Err(TryReceiveError::Done) => { assert!(false); },
        }
    }

    handle.join().unwrap();

    assert_eq!(var.load(Ordering::SeqCst), 1);
}

#[test]
fn test_request_threaded_receive() {
    let (rqst, resp) = channel::<Task>();

    let var = Arc::new(AtomicUsize::new(0));
    let var2 = var.clone();

    let handle = thread::spawn(move || {
        let mut contract = rqst.try_request().unwrap();

        loop {
            match contract.try_receive() {
                Ok(task) => {
                    task.call_box();
                    break;
                },
                Err(TryReceiveError::Empty) => {},
                Err(TryReceiveError::Done) => { assert!(false); },
            }
        }
    });

    loop {
        match resp.try_respond() {
            Ok(contract) => {
                contract.send(Box::new(move || {
                    var2.fetch_add(1, Ordering::SeqCst);
                }) as Task);
                break;
            },
            Err(TryRespondError::NoRequest) => {},
            Err(TryRespondError::Locked) => { assert!(false); },
        }
    }

    handle.join().unwrap();

    assert_eq!(var.load(Ordering::SeqCst), 1);
}

#[test]
fn test_request_threaded_receive_threaded() {
    let (rqst, resp) = channel::<Task>();

    let var = Arc::new(AtomicUsize::new(0));
    let var2 = var.clone();

    let handle1 = thread::spawn(move || {
        let mut contract = rqst.try_request().unwrap();

        loop {
            match contract.try_receive() {
                Ok(task) => {
                    task.call_box();
                    break;
                },
                Err(TryReceiveError::Empty) => {},
                Err(TryReceiveError::Done) => { assert!(false); },
            }
        }
    });

    let handle2 = thread::spawn(move || {
        loop {
            match resp.try_respond() {
                Ok(contract) => {
                    contract.send(Box::new(move || {
                        var2.fetch_add(1, Ordering::SeqCst);
                    }) as Task);
                    break;
                },
                Err(TryRespondError::NoRequest) => {},
                Err(TryRespondError::Locked) => { assert!(false); },
            }
        }
    });

    handle1.join().unwrap();
    handle2.join().unwrap();

    assert_eq!(var.load(Ordering::SeqCst), 1);
}