(*  let d := default_val _ in *)

Lemma nested_ufieldlist_at_ramif: forall sh t gfs id a i v p,
let d := default_val _ in
nested_field_type t gfs = Tunion id a ->
in_members i (co_members (get_co id)) ->
nested_ufieldlist_at sh t gfs (co_members (get_co id)) v p |--
field_at sh t (UnionField i :: gfs)
(proj_union i (co_members (get_co id)) v d) p *
(ALL v0: _,
field_at sh t (UnionField i :: gfs) v0 p -*
nested_ufieldlist_at sh t gfs (co_members (get_co id))
(upd_union i (co_members (get_co id)) v v0) p).