Instance CompSpecs : compspecs.Definition Vprog : varspecs.Definition t_struct_tree := Tstruct _tree noattr.Definition key := Z.Inductive tree : Type :=
 | E : tree
 | T: tree -> key -> V -> tree -> tree.Inductive tree : Type :=
 | E : tree
 | T: tree -> key -> V -> tree -> tree.Inductive tree : Type :=
 | E : tree
 | T: tree -> key -> V -> tree -> tree.Definition empty_tree : tree := E.Fixpoint pushdown_left (a: tree) (bc: tree) : tree :=
 match bc with
 | E => a
 | T b y vy c => T (pushdown_left a b) y vy c
 end.

Lemma is_pointer_or_null_force_val_sem_cast_neutral: forall p, is_pointer_or_null p -> force_val (sem_cast_neutral p) = p.