Section Properties.
Implicit Types x y : TVar.
Implicit Types xs ys : list TVar.
(* ---------------------------------------------------------------------- *)
(** **** Abstract properties of ok *)
(* ---------------------------------------------------------------------- *)
(** **** Properties of binds *)

(** Decidability of binds. *)
Theorem binds_dec_exists : forall A x (E : gen_env A),
{ v | x ∹ v ⋲ E } + { forall v, ¬ x ∹ v ⋲ E }.