Streaming/delta-streaming for script values.

I'm not saying its wrong but I don't understand why it would return 'true' if second is not valid... unless we know first is also invalid (and two invalid entries are considered equal (are they?))... but it is not clear to me that first is invalid... unless this is known to be true because all possibilities have been exhausted.  If I've got to go through all of this logic to understand maybe there should be a helpful comment here saying something like "first must be invalid therefore...".

This does not block the merge.