proposition: Lemma fresh_mid_tail : uniq (F ++ (one (VarAsn B x a)) ++ E) -> x `notin` dom E.
proof: Proof. clear. solve_uniq. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics