Opaque member_dec.

Lemma union_pred_ramif: forall m {A} (P: forall it, A it -> val -> mpred) (i: ident) v p d,
(forall i' (v': A (i', field_type i' m)), in_members i' m -> P _ v' p |-- P _ d p) ->
in_members i m ->
members_no_replicate m = true ->
union_pred m P v p |--
P _ (proj_union i m v d) p *
(ALL v0: _, P _ v0 p -* union_pred m P (upd_union i m v v0) p).