Hint Extern 0 (RIntro _ (forall_relation _) _ _) =>
eapply forall_relation_rintro : typeclass_instances.

Lemma forall_relation_relim {A B} (R: forall a:A, relation (B a)) f g a P Q:
RElim (R a) (f a) (g a) P Q ->
RElim (forall_relation R) f g P Q.