type ('a, 'b, 'c) pattern
= ('a, 'b, 'c) t
type ('a, 'b) t
val create : ('a, 'b, 'c) pattern ‑> 'b ‑> ('a, 'c) t
val parse : ('a, 'b) t ‑> Location.t ‑> 'a ‑> 'b