proposition: Lemma subst_exp_close_exp_wrt_exp_rec_mutual : (forall e2 e1 x1 x2 n1, degree_exp_wrt_exp n1 e1 -> x1 <> x2 -> x2 `notin` fv_exp e1 -> subst_exp e1 x1 (close_exp_wrt_exp_rec n1 x2 e2) = close_exp_wrt_exp_rec n1 x2 (subst_exp e1 x1 e2)).
proof: Proof. apply_mutual_ind exp_mutind; default_simp. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc