code: public NotificationChain basicSetGuard(Expression newGuard, NotificationChain msgs)
    {
      Expression oldGuard = guard;
      guard = newGuard;
      if (eNotificationRequired())
      {
        ENotificationImpl notification = new ENotificationImpl(this, Notification.SET, SimpleAntlrPackage.RULE_ELEMENT__GUARD, oldGuard, newGuard);
        if (msgs == null) msgs = notification; else msgs.add(notification);
      }
      return msgs;
    }
docs: <!-- begin-user-doc -->
  <!-- end-user-doc -->
  @generated