code: public void setGuard(Expression newGuard)
    {
      if (newGuard != guard)
      {
        NotificationChain msgs = null;
        if (guard != null)
          msgs = ((InternalEObject)guard).eInverseRemove(this, EOPPOSITE_FEATURE_BASE - SimpleAntlrPackage.RULE_ELEMENT__GUARD, null, msgs);
        if (newGuard != null)
          msgs = ((InternalEObject)newGuard).eInverseAdd(this, EOPPOSITE_FEATURE_BASE - SimpleAntlrPackage.RULE_ELEMENT__GUARD, null, msgs);
        msgs = basicSetGuard(newGuard, msgs);
        if (msgs != null) msgs.dispatch();
      }
      else if (eNotificationRequired())
        eNotify(new ENotificationImpl(this, Notification.SET, SimpleAntlrPackage.RULE_ELEMENT__GUARD, newGuard, newGuard));
    }
docs: <!-- begin-user-doc -->
  <!-- end-user-doc -->
  @generated