module type POLYMORPHIC2 =Same assig
..end
POLYMORPHIC
for types with two type variables.type ('a, 'b)
poly
val instantiate : 'a Type.t -> 'b Type.t -> ('a, 'b) poly Type.t
val is_instance_of : 'a Type.t -> bool
val get_instance : ('a, 'b) poly Type.t -> 'a Type.t * 'b Type.t