Thanks very much for following this through. And spotting my silly error - which is to not notice that the third clause is recursive (as it needs to be). I know that the number can’t be converted to an integer, I just couldn’t see why it wouldn’t match on the third clause. And indeed it does match on the first pass. I missed that it was recursing and not matching on a later pass (in fact there is an accepted PR that handles this error case better then the published version).
Thanks again.
