intros.
unfold as_tree in H.
repeat
match goal with
| [ H : match ?x with _ => _  end = _ |- _ ] => destruct x; simpl in H;  try congruence end.
inversion H. subst. auto.
Admitted.
Ltac destruct_as_tree :=
repeat
match goal with
| [ H : context [ match as_tree ?x with _ => _ end] |- _] => destruct (as_tree x) eqn:?
| [ H : as_tree _ = Some (inl (_ , _ , _, _)) |- _ ] => apply as_tree_l in H
| [ H : as_tree _ = Some (inr _) |- _ ] => apply as_tree_r in H
| [ H : as_tree _ = Some (inl (?p, _, _)) |- _ ] => destruct p
| [ H : as_tree _ = Some (inl (?p, _)) |- _ ] => destruct p
| [ H : as_tree _ = Some (inl ?p) |- _ ] => destruct p
| [ H : as_tree _ = Some ?p |- _ ] => destruct p
end;
subst.
Ltac solve_exprD := solve_exprD.solve_exprD tbl.
Opaque type_cast.

Lemma get_reif_val_exists :
forall i tr typ tus tvs vtr,
exprD' tus tvs (typtree typ) tr = Some vtr ->
exists v, exprD' tus tvs (tyoption typ) (get_reif i tr typ) = Some v.