Hint Resolve treebox_rep_saturate_local: saturate_local.
Definition insert_inv (b0: val) (t0: tree val) (x: Z) (v: val): environ -> mpred :=
EX b: val, EX t: tree val,
PROP()
LOCAL(temp _t b; temp _x (Vint (Int.repr x));   temp _value v)
SEP(treebox_rep t b;  (treebox_rep (insert x v t) b -* treebox_rep (insert x v t0) b0)).

Lemma tree_rep_nullval: forall t,
tree_rep t nullval |-- !! (t = E).