Module Types.Variance

type t
type f =
  1. | May_pos
  2. | May_neg
  3. | May_weak
  4. | Inj
  5. | Pos
  6. | Neg
  7. | Inv
val null : t
val full : t
val covariant : t
val unknown : t
val union : t -> t -> t
val inter : t -> t -> t
val subset : t -> t -> bool
val eq : t -> t -> bool
val set : f -> t -> t
val set_if : bool -> f -> t -> t
val mem : f -> t -> bool
val conjugate : t -> t
val compose : t -> t -> t
val strengthen : t -> t
val get_upper : t -> bool * bool
val get_lower : t -> bool * bool * bool
val unknown_signature : injective:bool -> arity:int -> t list

The most pessimistic variance for a completely unknown type.