Definition value_fits: forall t, reptype t -> Prop :=
  type_func (fun t => reptype t -> Prop)
    (fun t v =>
       if type_is_volatile t then True else tc_val' t (repinject t v))
    (fun t n a P v => Zlength (unfold_reptype v) =  Z.max 0 n /\ Forall P (unfold_reptype v))
    (fun id a P v => struct_value_fits_aux (co_members (get_co id)) (co_members (get_co id)) P (unfold_reptype v))
    (fun id a P v => union_value_fits_aux (co_members (get_co id)) (co_members (get_co id)) P (unfold_reptype v)).

Lemma value_fits_type_changable: forall (t1 t2: type) v1 v2, t1 = t2 -> JMeq v1 v2 -> value_fits t1 v1 = value_fits t2 v2.