WA has no duty to inform, further you have no duty to answer questions not directly connected to the investigation the Officer is conducting. If you're stopped for a traffic violation and the Officer asks if you have any firearms in the vehicle you are not obligated to answer and refusing to answer is not grounds for RS let alone PC.
However should the Officer learn that you are lawfully armed the courts have ruled that an Officer may secure a lawfully carried firearm if the Officer feels it necessary to insure the Officers safety. Some Officers abuse this discretionary ruling of the courts as blanket policy. Some LEO feel that every lawfully armed citizen is a threat to their personal safety, these are Officers that should not be Officers.