Hint Resolve tree_rep_nullval: saturate_local.

Lemma treebox_rep_leaf: forall x p b (v: val),
is_pointer_or_null v ->
Int.min_signed <= x <= Int.max_signed ->
field_at Tsh t_struct_tree [] (Vint (Int.repr x), (v, (nullval, nullval))) p *
field_at Tsh (tptr t_struct_tree) [] p b |-- treebox_rep (T E x v E) b.