Ltac solve_JMeq_sumtype H :=
  match type of H with
  | JMeq ?x ?y =>
    destruct x; destruct y;
     [apply JMeq_sumtype_ll in H; auto
     |apply JMeq_sumtype_lr in H; auto; inversion H
     |apply JMeq_sumtype_rl in H; auto; inversion H
     |apply JMeq_sumtype_rr in H; auto]
  end.

Lemma list_func_JMeq: forall {A: Type} {B: Type} {C: Type} (a: list A) (b: list B) (f: forall X, list X -> C), @eq Type A B -> JMeq a b -> f A a = f B b.