Fixpoint find_id (id: ident) (G: funspecs) : option funspec  :=
 match G with
 | (id', f)::G' => if eq_dec id id' then Some f else find_id id G'
 | nil => None
 end.

Lemma find_id_i: forall id fs G, In (id,fs) G -> list_norepet (map (@fst _ _) G) -> find_id id G = Some fs.