Module `Arg.Ty`

type 'a witness = ..

exception Not_equal

type (_, _) eq = | Eq : ('a, 'a) eq

module type Ty = sig ... end

type 'a id = (module Ty with type t = 'a)

val new_id : unit -> (module Ty with type t = 'a)
val eq : a b. 'a id -> 'b id -> ('a, 'b) eq