docs: @Override
  	public XExpression getArgument()
  	{
  		if (argument != null && argument.eIsProxy())
  		{
  			InternalEObject oldArgument = (InternalEObject)argument;
  			argument = (XExpression)eResolveProxy(oldArgument);
  			if (argument != oldArgument)
  			{
  				if (eNotificationRequired())
  					eNotify(new ENotificationImpl(this, Notification.RESOLVE, SarlPackage.SARL_CASTED_EXPRESSION__ARGUMENT, oldArgument, argument));
  			}
  		}
  		return argument;
  	}