Hint Resolve PROP_later_derives LOCAL_later_derives SEP_later_derives : derives.

Lemma extract_exists_post:
forall {Espec: OracleKind} {cs: compspecs} {A: Type} (x: A) Delta
(P: environ -> mpred) c (R: A -> environ -> mpred),
semax Delta P c (normal_ret_assert (R x)) ->
semax Delta P c (normal_ret_assert (exp R)).