proposition: Lemma fv_exp_close_exp_wrt_exp_rec_mutual : (forall e1 x1 n1, fv_exp (close_exp_wrt_exp_rec n1 x1 e1) [=] remove x1 (fv_exp e1)).
proof: Proof. apply_mutual_ind exp_mutind; default_simp; fsetdec. Qed.
imports: Coq.Logic.FunctionalExtensionality Coq.Program.Equality Metalib.Metatheory Metalib.LibLNgen Stlc