Throw an error if calling parser recursively

Throw an error if calling parser recursively

People accidentally (or sometimes intentionally) calling the
parser recursively has been a major source of bugs over the
years. I think its much better to fail suddenly, instead
of having unclear signs like UNIQ's all over the place.

Change-Id: I0e42aa69835c15a5df7aecb0dc5c3dec946bdf6a