Section FancyUpdates.
Context {inv_names : invG}.
Definition fupd (E1 E2 : Ensemble iname) P :=
(wsat * ghost_set g_en E1) -* |==> except0 (wsat * ghost_set g_en E2 * P).
Notation "|={ E1 , E2 }=> P" := (fupd E1 E2 P) (at level 62): logic.
Notation "|={ E }=> P" := (fupd E E P) (at level 62): logic.

Lemma inv_open : forall E i P, In E i ->
invariant i P |-- |={E, Subtract E i}=> (|> P) * (|>P -* |={Subtract E i, E}=> emp).