/**
* Simplify an expression
*
* @return the simplified expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) {
if (axis == Axis.PARENT && (test == null || test instanceof AnyNodeTest)) {
ParentNodeExpression p = new ParentNodeExpression();
ExpressionTool.copyLocationInfo(this, p);
return p;
}
return this;
}
/** Type-check the expression */
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
throws XPathException {
Configuration config = visitor.getConfiguration();
NamePool namePool = config.getNamePool();
StaticContext env = visitor.getStaticContext();
if (contextItemType == null) {
typeError(
visitor,
"Axis step " + toString(namePool) + " cannot be used here: the context item is undefined",
"XPDY0002",
null);
}
if (contextItemType.isAtomicType()) {
typeError(
visitor,
"Axis step "
+ toString(namePool)
+ " cannot be used here: the context item is an atomic value",
"XPTY0020",
null);
}
if (this.contextItemType == contextItemType && doneWarnings) {
return this;
}
this.contextItemType = contextItemType;
doneWarnings = true;
if (contextItemType instanceof NodeTest) {
int origin = contextItemType.getPrimitiveType();
if (origin != Type.NODE) {
if (Axis.isAlwaysEmpty(axis, origin)) {
env.issueWarning(
"The "
+ Axis.axisName[axis]
+ " axis starting at "
+ (origin == Type.ELEMENT || origin == Type.ATTRIBUTE ? "an " : "a ")
+ NodeKindTest.nodeKindName(origin)
+ " node will never select anything",
getSourceLocator());
return Literal.makeEmptySequence();
}
}
if (test != null) {
int kind = test.getPrimitiveType();
if (kind != Type.NODE) {
if (!Axis.containsNodeKind(axis, kind)) {
env.issueWarning(
"The "
+ Axis.axisName[axis]
+ " axis will never select any "
+ NodeKindTest.nodeKindName(kind)
+ " nodes",
getSourceLocator());
return Literal.makeEmptySequence();
}
}
if (axis == Axis.SELF && kind != Type.NODE && origin != Type.NODE && kind != origin) {
env.issueWarning(
"The self axis will never select any "
+ NodeKindTest.nodeKindName(kind)
+ " nodes when starting at "
+ (origin == Type.ELEMENT || origin == Type.ATTRIBUTE ? "an " : "a ")
+ NodeKindTest.nodeKindName(origin)
+ " node",
getSourceLocator());
return Literal.makeEmptySequence();
}
if (axis == Axis.SELF) {
itemType = new CombinedNodeTest(test, Token.INTERSECT, (NodeTest) contextItemType);
}
// If the content type of the context item is known, see whether the node test can select
// anything
if (contextItemType instanceof DocumentNodeTest && kind == Type.ELEMENT) {
NodeTest elementTest = ((DocumentNodeTest) contextItemType).getElementTest();
Set<Integer> outermostElementNames = elementTest.getRequiredNodeNames();
if (outermostElementNames != null) {
Set<Integer> selectedElementNames = test.getRequiredNodeNames();
if (selectedElementNames != null) {
if (axis == Axis.CHILD) {
// check that the name appearing in the step is one of the names allowed by the
// nodetest
if (SetUtils.intersect(selectedElementNames, outermostElementNames).isEmpty()) {
env.issueWarning(
"Starting at a document node, the step is selecting an element whose name "
+ "is not among the names of child elements permitted for this document node type",
getSourceLocator());
return Literal.makeEmptySequence();
}
itemType = elementTest;
return this;
} else if (axis == Axis.DESCENDANT) {
// check that the name appearing in the step is one of the names allowed by the
// nodetest
boolean canMatchOutermost =
!SetUtils.intersect(selectedElementNames, outermostElementNames).isEmpty();
if (!canMatchOutermost) {
// The expression /descendant::x starting at the document node doesn't match the
// outermost
// element, so replace it by child::*/descendant::x, and check that
PathExpression path =
new PathExpression(
new AxisExpression(Axis.CHILD, elementTest),
new AxisExpression(Axis.DESCENDANT, test));
ExpressionTool.copyLocationInfo(this, path);
return path.typeCheck(visitor, contextItemType);
}
}
}
}
}
}
}
return this;
}