proposition: Lemma change_bvars_rangewspec: forall (lva : list (vType vc)) (sub: SSubstitution vc), {sr : SSubstitution vc $ sub === sr # disjoint (flat_map (tBndngVarsDeep vc) (ALRange sr)) lva}.
proof: Proof. intros. eexists; apply change_bvars_range_spec. Qed.
imports: SubstAuxAlphaEq AlphaRen Term