As reported by Tal Liron at http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-August/003307.html

The following program will cause an exception when "isEmpty2" is called:

 Error: java.lang.ClassCastException: java.lang.String cannot be cast to jdk.nashorn.internal.runtime.Undefined

The only difference between isEmpty1 and isEmpty2 is the actual use of "k". If "k" is not referenced, the exception happens.


function isEmpty1(v) {
 for (var k in v) {
   print(v[k]+'\n')
   return false
 }
 return true
}

function isEmpty2(v) {
 for (var k in v) {
   return false
 }
 return true
}

x = {test: 'test'}

isEmpty1(x)
isEmpty2(x)