Opaque member_dec.

Lemma struct_pred_ramif: forall m {A} (P: forall it, A it -> val -> mpred) (i: ident) v p d,
in_members i m ->
members_no_replicate m = true ->
struct_pred m P v p |--
P _ (proj_struct i m v d) p *
(ALL v0: _, P _ v0 p -* struct_pred m P (upd_struct i m v v0) p).