proposition: Lemma sepcon_unique_vertex_at sh: writable_share sh -> sepcon_unique2 (@vertex_at _ _ _ _ _ (SGP_VST sh)).
proof: Proof. intros. hnf; intros. simpl. destruct y1 as [? ?], y2 as [? ?]. unfold binode. rewrite data_at_isptr. normalize. apply data_at_conflict. + apply readable_nonidentity, writable_readable. auto. + change (sizeof node_type) with (if Archi.ptr64 then 16 else 8). cbv [Archi.ptr64]. lia. Qed.
imports: CertiGraph.msl_ext.iter_sepcon CertiGraph.msl_application.Graph CertiGraph.msl_application.GList VST.veric.SeparationLogic CertiGraph.unionfind.env_unionfind CertiGraph.floyd_ext.share