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

(** Binds and remove. *)
Theorem binds_remove : forall A x y (v : A) (E : gen_env A),
x <> y -> x ∹ v ⋲ E ->
x ∹ v ⋲ (E ∖ {y}).