proposition: Lemma eq_single_inv : forall x1 x2 v1 v2, x1 ~ v1 = x2 ~ v2 -> x1 = x2 /\ v1 = v2.
proof: Proof. Proof using. introv H. rew_env_defs. inverts~ H. Qed.
imports: TLC(LibTactics LibOption LibList LibProd LibLogic LibReflect)