anchor.diff:  	|	message
   	|	enum_def
   	|	flags_def
  -    |   extensions
  -    |   reservations
   	;
   
   extensions
  
positive.code:     {
          initSymbolTable(SCOPE_TOP(Symbols), $message::messageName, $message::isExtension);  
      }
  	:	message_element zero_or_more_message_elements
      {
          if($message::isExtension) {
              defineExtensionEnd(ctx, $message::messageName);
  
negative.code:         }
          ;
  
  reservations : (RESERVE integer TO integer_inclusive ITEM_TERMINATOR -> WS[""])
          {
              defineReservedRange(ctx, $integer.text, $integer_inclusive.text);
          }
  