[cl-sdl-help] another "%sap-alien warning" question

[David M. <dc...@gm...>]

Sorry to raise such a similar issue to one that keeps coming up.

In sbcl calls to 
(sdl:event-mouse-motion-x event)
generate a warning about inefficient runtime-compile-invoking
%sap-alien conversions.  I've tried to properly declare my event, ala:
  (declare (type event-ptr event))
where I've already evaluated the top level form 
  (uffi:def-type event-ptr '(* sdl:event))
But I still seem to get the warning.  Is this because a pointer to a
mouse-motion-event is an even narrower subtype of a pointer to an
event?  Is there some magic declaration I can use to make it shut up? 
I tried
    (uffi:def-type motion-event-ptr '(* sdl:mouse-motion-event))
and though it evaluated fine, I still get the pesky warning.