I believe it needs to be this: 

> the error should be propagated and all future sequences produced by the parent sequence should be ignored (unsubscribed)

It's the same way with `merge`, `zip`, etc. If an error occurs on any sequence it immediately kills the entire sequence and passes the error.

I could see an overload of `switch` existing that could add behavior such as `onErrorResumeNext` so that the user can choose whether to ignore the error and just `switch` to the next sequence, or handle it with a default or something else before switching, etc.

We can't just swallow errors though so if an onError is received from a child sequence it must behave as if the parent received an onError and unsubscribe and pass on the error.