Function primal_crossbeam::primes_unbounded

pub fn primes_unbounded() -> (impl FnOnce() + Send, Receiver<usize>)

let (thread, r) = thread_spawn(primes_unbounded());
assert_eq!(r.recv(), Ok(2));
assert_eq!(r.recv(), Ok(3));
assert_eq!(r.recv(), Ok(5));
// thread.join(); // Would block indefinitely
drop(r);
thread.join();