michael@0: function f(a) {
michael@0:    function g() {
michael@0:        yield function () a;
michael@0:    }
michael@0:    if (a == 8)
michael@0:        return g();
michael@0:    a = 3;
michael@0: }
michael@0: var x;
michael@0: for (var i = 0; i < 9; i++)
michael@0:    x = f(i);
michael@0: x.next()();  // ReferenceError: a is not defined.