proposition: Lemma close_exp_wrt_exp_inj : forall e1 e2 x1, close_exp_wrt_exp x1 e1 = close_exp_wrt_exp x1 e2 -> e1 = e2.
proof: Proof. unfold close_exp_wrt_exp; eauto with lngen. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc