Hint Rewrite eval_cast_neutral_isptr using assumption : norm.
Arguments ret_type !Delta /.
Arguments Datatypes.id {A} x / .

Lemma lift_lift_retval:
forall (i: ident) P,
@liftx (Tarrow environ (LiftEnviron mpred))
(@liftx (Tarrow val (LiftEnviron mpred)) P retval) (get_result1 i) = `P (eval_id i).