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

Theorem binds_singles_inv : forall A x y (v w : A) ys (ws : list A),
x ∹ v ⋲ (y :: ys ∷ w :: ws) ->
(x = y ∧ v = w) ∨ (x ∹ v ⋲ (ys ∷ ws)).