destruct (@binds_cons_1 _ c0 c _ (Co phi) G H2) as [[E1 E2] | E3].
    + subst. simpl. eauto.
    + simpl. eapply binds_cons_3. auto.
Qed.Definition AnnTyping_erase :
  (forall G a A, AnnTyping G a A ->
            Typing (erase_context G) (erase a) (erase A)) := first erase_mutual.
Definition AnnPropWff_erase :
  (forall G phi, AnnPropWff G phi ->
            PropWff (erase_context G) (erase phi)) := second erase_mutual.
Definition AnnIso_erase :(forall G D g p1 p2, AnnIso G D g p1 p2 ->
          Iso (erase_context G) D
              (erase_constraint p1) (erase_constraint p2)) := third erase_mutual.
Definition AnnDefEq_erase :
  (forall G D g a b,AnnDefEq G D g a b ->
      forall A, AnnTyping G a A ->
           DefEq (erase_context G) D (erase a) (erase b) (erase A)) := fourth erase_mutual.

exists (a_Conv a g). repeat split. eauto. Qed.