public XmlQueryType CheckError(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.StringX);
     return XmlQueryTypeFactory.None;
 }

 public XmlQueryType CheckXPathPreceding(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtf);
     return XmlQueryTypeFactory.ContentS;
 }

 //-----------------------------------------------
 // XSLT
 //-----------------------------------------------
 public XmlQueryType CheckXsltGenerateId(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtfS);
     return XmlQueryTypeFactory.StringX;
 }

 public XmlQueryType CheckPrefixOf(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.Node);
     return XmlQueryTypeFactory.StringX;
 }

 public XmlQueryType CheckIsEmpty(QilUnary node) {
     return XmlQueryTypeFactory.BooleanX;
 }

 public XmlQueryType CheckRawTextCtor(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.StringX);
     return XmlQueryTypeFactory.Text;
 }

 //-----------------------------------------------
 // Node properties
 //-----------------------------------------------
 public XmlQueryType CheckNameOf(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.Node);
     return XmlQueryTypeFactory.QNameX;
 }

 public XmlQueryType CheckMaximum(QilUnary node) {
     return CheckAverage(node);
 }

 //-----------------------------------------------
 // arithmetic operators
 //-----------------------------------------------
 public XmlQueryType CheckNegate(QilUnary node) {
     CheckNumericX(node.Child);
     return node.Child.XmlType;
 }

 //-----------------------------------------------
 // collection operators
 //-----------------------------------------------
 public XmlQueryType CheckLength(QilUnary node) {
     return XmlQueryTypeFactory.IntX;
 }

 public XmlQueryType CheckAverage(QilUnary node) {
     XmlQueryType xmlType = node.Child.XmlType;
     CheckNumericXS(node.Child);
     return XmlQueryTypeFactory.PrimeProduct(xmlType, xmlType.MaybeEmpty ? XmlQueryCardinality.ZeroOrOne : XmlQueryCardinality.One);
 }

 public XmlQueryType CheckNot(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.BooleanX);
     return XmlQueryTypeFactory.BooleanX;
 }

 public XmlQueryType CheckPositionOf(QilUnary node) {
     return XmlQueryTypeFactory.IntX;
 }

 public XmlQueryType CheckWarning(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.StringX);
     return XmlQueryTypeFactory.Empty;
 }

 public XmlQueryType CheckAncestorOrSelf(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtf);
     return XmlQueryTypeFactory.Choice(node.Child.XmlType, XmlQueryTypeFactory.DocumentOrElementS);
 }

 //-----------------------------------------------
 // string operators
 //-----------------------------------------------
 public XmlQueryType CheckStrLength(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.StringX);
     return XmlQueryTypeFactory.IntX;
 }

 public XmlQueryType CheckFollowingSibling(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtf);
     return XmlQueryTypeFactory.ContentS;
 }

 public XmlQueryType CheckDocOrderDistinct(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtfS);
     return DistinctType(node.Child.XmlType);
 }

 public XmlQueryType CheckDocumentCtor(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtfS);
     return XmlQueryTypeFactory.UntypedDocument;
 }

 //-----------------------------------------------
 // XML navigation
 //-----------------------------------------------
 public XmlQueryType CheckContent(QilUnary node) {
     CheckXmlType(node.Child, XmlQueryTypeFactory.NodeNotRtf);
     return XmlQueryTypeFactory.AttributeOrContentS;
 }