Univ.Variance
type t
=

Irrelevant
Covariant
Invariant
A universe position in the instance given to a cumulative inductive can be the following. Note there is no Contravariant case because forall x : A, B <= forall x : A', B' requires A = A' as opposed to A' <= A.
forall x : A, B <= forall x : A', B'
A = A'
A' <= A
val check_subtype : t > t > bool
check_subtype x y holds if variance y is also an instance of x
check_subtype x y
y
x
val sup : t > t > t
val pr : t > Pp.t
val equal : t > t > bool