Definition tc_fn_return (Delta: tycontext) (ret: option ident) (t: type) :=
match ret with
| None => True
| Some i => match (temp_types Delta) ! i with Some t' => t=t' | _ => False end
end.

Lemma derives_refl' {A: Type}  `{ageable A}:
forall P Q: pred A, P=Q -> P |-- Q.