type ('self, 'trec, 'f, 'r) t
val stop : ('self, norec, 'r, 'r) tval next : ('self, _, 'a, 'r) t -> ('self, _, 'b) Symbol.t -> ('self, mayrec, 'b -> 'a, 'r) tval next_norec : ('self, norec, 'a, 'r) Rule.t -> ('self, norec, 'b) Symbol.t -> ('self, norec, 'b -> 'a, 'r) t