Module Accessor.Identical
An Identical.t is similar to a Type_equal.t, but it relates two pairs of types with each other instead of merely two types. It is a more natural way of using an equality accessor than Type_equal.t would be, since you only need to match on one constructor.
type ('a, 'b, 'at, 'bt) t=|T : ('a, 'b, 'a, 'b) t