Saxon

Similar error in the interpreted code:

java.lang.ClassCastException: net.sf.saxon.value.StringValue cannot be cast to net.sf.saxon.om.NodeInfo
	at net.sf.saxon.functions.KeyFn.iterate(KeyFn.java:276)
	at net.sf.saxon.expr.Atomizer.iterate(Atomizer.java:319)
	at net.sf.saxon.expr.AtomicSequenceConverter.iterate(AtomicSequenceConverter.java:244)
	at net.sf.saxon.functions.FoldingFunction.evaluateItem(FoldingFunction.java:56)
	at net.sf.saxon.expr.Expression.evaluateAsString(Expression.java:533)
	at net.sf.saxon.expr.instruct.SimpleNodeConstructor.processLeavingTail(SimpleNodeConstructor.java:230)
	at net.sf.saxon.expr.instruct.ValueOf.processLeavingTail(ValueOf.java:282)
	at net.sf.saxon.expr.instruct.Block.processLeavingTail(Block.java:672)
	at net.sf.saxon.expr.instruct.Template.expand(Template.java:371)
	at net.sf.saxon.Controller.transformDocument(Controller.java:2119)
	at net.sf.saxon.Controller.transform(Controller.java:1705)
	at net.sf.saxon.s9api.XsltTransformer.transform(XsltTransformer.java:547)
	at net.sf.saxon.Transform.processFile(Transform.java:1056)
	at net.sf.saxon.Transform.doTransform(Transform.java:659)
	at net.sf.saxon.Transform.main(Transform.java:80)

Just for the record: there's a fairly convoluted path here from cause to effect.

There's a filter expression of the form $doc/a/b/c[d='f'] where $doc is a reference to a global variable. The optimizer turns this into a call on key(), and constructs a key definition that indexes $doc on the value of /a/b/c. Both the call on key() and the key definition include references to $doc, but instead of containing separate variable references, they share the same variable reference. But because the template and the key definition are separate components, they each need a separate binding slot for this global reference. So one of the slot numbers is wrong, which means that when the key() call is evaluated, the wrong global variable is read, and this has the wrong type, which causes a cast to fail during evaluation of generated byte code. When byte code is switched off, it fails with slightly different symptoms. The solution is to create a copy of the variable reference rather than sharing it.