sig
type t
val empty : cstr:Constraint.t -> Literal.ClosureSet.t
val add : Literal.ClosureSet.t -> key:substituable -> Literal.ClosureSet.t
val closure_applies : Literal.ClosureSet.t -> key:substituable -> bool
val add_constraint :
Literal.ClosureSet.t -> cstr:Constraint.t -> Literal.ClosureSet.t
end