Module ESF2 := FSetFacts.Facts(EqSet2).
Module ESP2 := FSetProperties.Properties(EqSet2).
Module ESD2 := FSetDecide.Decide(EqSet2).

Lemma in_subst_loc:
forall l1 l2 q (e e': eqs),
EqSet.In q e ->
subst_loc l1 l2 e = Some e' ->
(eloc q = l1 /\ EqSet.In (Eq (ekind q) (ereg q) l2) e') \/ (Loc.diff l1 (eloc q) /\ EqSet.In q e').