Admitted. (* QuickChick t_update_same *)

(* Specifications: *)
Theorem t_update_permute : forall v1 v2 x1 x2
(m : total_map),
x2 <> x1 ->
(t_update (t_update m x2 v2) x1 v1)
= (t_update (t_update m x1 v1) x2 v2).