pub struct ThreadScope<'a> {

}

// Not sure about this, but doesn't seem necessary or
// particularly useful to be able to pass it to another thread
impl<'a> !Sync for ThreadScope<'a> { }

fn scope<'a,F,R>(f: F) -> R
    where F: FnOnce(&ThreadScope<'a>)

impl ThreadScope<'a> {
    fn spawn<F,R>(&self, f: F) -> Future<'a,R>
        where F: FnOnce()->R + Send + 'a
}

struct Future<'a,R> {
}

impl<'a,R> Future<'a,R> {
    fn join(self) -> R
}