Ltac solve_field_offset_type i m :=
  let H := fresh "H" in
  let Hty := fresh "H" in
  let Hofs := fresh "H" in
  let t := fresh "t" in
  let ofs := fresh "ofs" in
  pose proof field_offset_field_type_match cenv_cs i m;
  destruct (Ctypes.field_offset cenv_cs i m) as [ofs|?] eqn:Hofs, (Ctypes.field_type i m) as [t|?] eqn:Hty;
    [clear H | inversion H | inversion H | clear H].

Lemma map_members_ext: forall A (f f':ident * type -> A) (m: members), members_no_replicate m = true -> (forall i, in_members i m -> f (i, field_type i m) = f' (i, field_type i m)) -> map f m = map f' m.