proposition: Lemma subst'_int (X:Set) (ty : TT X) (f:X) (H : computable f) : forall x t, subst' (ext f) x t = (ext f).
proof: Proof. intros. apply subst'_cls. Lproc. Qed.
imports: Undecidability.L(ComputableTactics Lproc Tactics.Computable Lrewrite)