propagate

    function

    (propagate x fib)

    Propagate a signal from a fiber `fib` to the current fiber and set 
    the last value of the current fiber to `x`. The signal value is 
    then available as the status of the current fiber. The resulting 
    stack trace from the current fiber will include frames from `fib`. 
    If `fib` is in a state that can be resumed, resuming the current 
    fiber will first resume `fib`. This function can be used to 
    re-raise an error without losing the original stack trace.