proposition: Lemma degree_exp_wrt_exp_open_exp_wrt_exp_inv : forall e1 e2, degree_exp_wrt_exp 0 (open_exp_wrt_exp e1 e2) -> degree_exp_wrt_exp 1 e1.
proof: Proof. unfold open_exp_wrt_exp; eauto with lngen. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc