module type With_Widening = sig .. end
sig
end
type t
type widen_hint
hints for the widening
val widen : widen_hint -> t -> t -> t
widen_hint -> t -> t -> t
widen h t1 t2 is an over-approximation of join t1 t2. Assumes is_included t1 t2
widen h t1 t2
join t1 t2
is_included t1 t2