(* field_offset2_in_range union's version *)

(* if sizeof Tvoid = 0, this lemma can be nicer. *)
Lemma field_offset_no_overlap:
forall i1 i2 m,
i1 <> i2 ->
in_members i1 m ->
in_members i2 m ->
field_offset cenv_cs i1 m + sizeof (field_type i1 m) <= field_offset cenv_cs i2 m \/
field_offset cenv_cs i2 m + sizeof (field_type i2 m) <= field_offset cenv_cs i1 m.