diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_6/Generators/delegating-yield-3.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_6/Generators/delegating-yield-3.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,40 @@
+// Test yield* with iter.next and monkeypatching.
+
+function* g(n) { for (var i=0; i<n; i++) yield i; }
+function* delegate(iter) { return yield* iter; }
+var GeneratorObjectPrototype = Object.getPrototypeOf(g).prototype;
+var GeneratorObjectPrototype_next = GeneratorObjectPrototype.next;
+
+// Monkeypatch next on an iterator.
+var inner = g(20);
+var outer = delegate(inner);
+assertIteratorNext(outer, 0);
+assertIteratorNext(outer, 1);
+inner.next = function() { return 0; };
+// 42 yielded directly without re-boxing.
+assertEq(0, outer.next());
+// Outer generator not terminated.
+assertEq(0, outer.next());
+// Restore.
+inner.next = GeneratorObjectPrototype_next;
+assertIteratorNext(outer, 2);
+// Repatch.
+inner.next = function() { return { value: 42, done: true }; };
+assertIteratorDone(outer, 42);
+
+// Monkeypunch next on the prototype.
+var inner = g(20);
+var outer = delegate(inner);
+assertIteratorNext(outer, 0);
+assertIteratorNext(outer, 1);
+GeneratorObjectPrototype.next = function() { return 0; };
+// 42 yielded directly without re-boxing.
+assertEq(0, GeneratorObjectPrototype_next.call(outer));
+// Outer generator not terminated.
+assertEq(0, GeneratorObjectPrototype_next.call(outer));
+// Restore.
+GeneratorObjectPrototype.next = GeneratorObjectPrototype_next;
+assertIteratorNext(outer, 2);
+
+if (typeof reportCompare == "function")
+    reportCompare(true, true);