default ParameterDeclaration asParameter(){
  throw new UnsupportedOperationException(String.format("%s is not a ParameterDeclaration",this));
}

default ParameterDeclaration asParameter ( ) { throw new UnsupportedOperationException ( String . format ( "%s is not a ParameterDeclaration" , this ) ) ; }
return this as a parameterdeclaration or throw an unsupportedoperationexception
