proposition: Lemma uniq_app_1 : uniq (E ++ F) -> uniq E.
proof: Proof. clear. intros H; induction E as [ | a E']; simpl_asnlist in *. apply uniq_nil. destruct a. apply uniq_push; inversion H; subst. auto. simpl_asnlist in *. fsetdec. apply uniq_alt; inversion H; subst. auto. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics