public XmlQueryType CheckSort(QilLoop node) {
XmlQueryType varType = node.Variable.Binding.XmlType;
CheckClassAndNodeType(node[0], typeof(QilIterator), QilNodeType.For);
CheckClassAndNodeType(node[1], typeof(QilList), QilNodeType.SortKeyList);
// Sort does not preserve DocOrderDistinct
if (varType.IsDod)
return XmlQueryTypeFactory.PrimeProduct(XmlQueryTypeFactory.NodeNotRtfS, varType.Cardinality);
return node.Variable.Binding.XmlType;
}