a signature for identifier types.
module type S_not_binable : sig ... end
module type S : sig ... end
module Make_using_comparator : functor (M : sig ... end) -> S with type t := M.t with type comparator_witness := M.comparator_witness
module Extend : functor (M : Base.Identifiable.S) -> functor (B : Core_kernel__.Binable0.S with type t = M.t) -> S with type t := M.t with type comparator_witness := M.comparator_witness