Make2.1-X
type ('a, 'e) t
val bind : ('a, 'e) t -> f:('a -> ('b, 'e) t) -> ('b, 'e) t
val map : [ `Define_using_bind | `Custom of ('a, 'e) t -> f:('a -> 'b) -> ('b, 'e) t ]
val return : 'a -> ('a, _) t