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

(** Binds on singular(s). *)
Theorem binds_single : forall A x y (v w : A),
x = y -> v = w ->
x ∹ v ⋲ (y ∶ w).