Saxon

Compiling this XQuery

declare function local:f($e, $n) 
{
  if (exists($e)) then
    $e
  else
    local:f(element e {string-join((1 to xs:integer($n/text())) ! "e")}, ())
};
local:f((), <n>10</n>)

with Saxon-EE 9.7.0.1 shows this:

com.saxonica.ee.bytecode.util.CannotCompileException: class net.sf.saxon.expr.instruct.FixedElement: <e {string-join((1 to (Q{http://www.w3.org/2001/XMLSchema}integer(atomizeSingleton(ConditionalSorter(exists(tail(($n) treat as node())), documentSort((($n) treat as node())/child::text())))))) ! "e")}/>
        at com.saxonica.ee.bytecode.LetExpressionCompiler.makeClosure(LetExpressionCompiler.java:630)
        at com.saxonica.ee.bytecode.LetExpressionCompiler.compileCommonExpr(LetExpressionCompiler.java:181)
        at com.saxonica.ee.bytecode.UserFunctionCallCompiler.compileFunctionCall(UserFunctionCallCompiler.java:65)
        at com.saxonica.ee.bytecode.UserFunctionCallCompiler.compileToIterator(UserFunctionCallCompiler.java:21)
        at com.saxonica.ee.bytecode.util.CompilerService.compileToIterator(CompilerService.java:760)
        at com.saxonica.ee.bytecode.ChooseCompiler.compileToIterator(ChooseCompiler.java:42)
        at com.saxonica.ee.bytecode.util.CompilerService.compileToIterator(CompilerService.java:760)
        at com.saxonica.ee.bytecode.TailCallLoopCompiler.compileToIterator(TailCallLoopCompiler.java:21)
        at com.saxonica.ee.bytecode.util.CompilerService.compileToIterator(CompilerService.java:760)
        at com.saxonica.ee.bytecode.util.CompilerService.compileToByteCode(CompilerService.java:508)
        at com.saxonica.ee.optim.OptimizerEE.compileToByteCode(OptimizerEE.java:1524)
        at net.sf.saxon.query.XQueryFunction.optimize(XQueryFunction.java:483)
        at net.sf.saxon.query.XQueryFunctionLibrary.optimizeGlobalFunctions(XQueryFunctionLibrary.java:328)
        at net.sf.saxon.query.QueryModule.optimizeGlobalFunctions(QueryModule.java:1200)
        at net.sf.saxon.expr.instruct.Executable.fixupQueryModules(Executable.java:574)
        at net.sf.saxon.query.XQueryParser.makeXQueryExpression(XQueryParser.java:161)
        at net.sf.saxon.query.StaticQueryContext.compileQuery(StaticQueryContext.java:589)
        at net.sf.saxon.query.StaticQueryContext.compileQuery(StaticQueryContext.java:652)
        at net.sf.saxon.s9api.XQueryCompiler.compile(XQueryCompiler.java:606)
        at net.sf.saxon.Query.compileQuery(Query.java:794)
        at net.sf.saxon.Query.doQuery(Query.java:342)
        at net.sf.saxon.Query.main(Query.java:111)
Exception in thread "main" java.lang.AssertionError: The Label: notInstanceOf has been used but not marked
        at com.saxonica.ee.bytecode.util.GeneratedMethodInfo.checkLabels(GeneratedMethodInfo.java:147)
        at com.saxonica.ee.bytecode.util.CompilerService.popCurrentMethodInfo(CompilerService.java:874)
        at com.saxonica.ee.bytecode.util.CompilerService.compileToByteCode(CompilerService.java:526)
        at com.saxonica.ee.optim.OptimizerEE.compileToByteCode(OptimizerEE.java:1524)
        at net.sf.saxon.query.XQueryFunction.optimize(XQueryFunction.java:483)
        at net.sf.saxon.query.XQueryFunctionLibrary.optimizeGlobalFunctions(XQueryFunctionLibrary.java:328)
        at net.sf.saxon.query.QueryModule.optimizeGlobalFunctions(QueryModule.java:1200)
        at net.sf.saxon.expr.instruct.Executable.fixupQueryModules(Executable.java:574)
        at net.sf.saxon.query.XQueryParser.makeXQueryExpression(XQueryParser.java:161)
        at net.sf.saxon.query.StaticQueryContext.compileQuery(StaticQueryContext.java:589)
        at net.sf.saxon.query.StaticQueryContext.compileQuery(StaticQueryContext.java:652)
        at net.sf.saxon.s9api.XQueryCompiler.compile(XQueryCompiler.java:606)
        at net.sf.saxon.Query.compileQuery(Query.java:794)
        at net.sf.saxon.Query.doQuery(Query.java:342)
        at net.sf.saxon.Query.main(Query.java:111)