Lemma body_pushdown_left: semax_body Vprog Gprog f_pushdown_left pushdown_left_spec.
Definition delete_inv (b0: val) (t0: tree val) (x: nat): environ -> mpred :=
EX b: val, EX t: tree val, EX P: tree val -> tree val,
PROP(P (delete x t) = delete x t0)
LOCAL(temp _t b; temp _x (Vint (Int.repr (Z.of_nat x))))
SEP(treebox_rep t b; partial_treebox_rep P b0 b).