[Lazarus] Confusing compiler hint on unused parameter

[Werner Pamler]

This compiler message looks strange to me: "tatextelements.pas(177,24) 
Hint: Value parameter "AValue" is assigned but never used". It occurs 
when TAChart is recompiled (see bug report #0027484). Here is the 
corresponding code:

procedure TGenericChartMarks.SetFrame(AValue: _TFramePen);
begin
   if FFrame = AValue then exit;
   FFrame.Assign(AValue);
   StyleChanged(Self);
end;

I would say that the parameter "AValue" *is* used. So, what is this hint 
for?