Definition substopt {A} (ret: option ident) (v: val) (P: environ -> A)  : environ -> A :=
match ret with
| Some id => subst id v P
| None => P
end.

Lemma bind_parameter_temps_excludes :
forall l1 l2 t id t1,
~In id (map fst l1) ->
(bind_parameter_temps l1 l2 t) = Some t1 ->
t1 ! id = t ! id.