michael@0: 
michael@0: x = 30;
michael@0: function foo() {
michael@0:   assertEq(x, 30);
michael@0:   delete x;
michael@0:   y = 20;
michael@0:   Object.defineProperty(this, 'x', {value:10});
michael@0:   assertEq(x, 10);
michael@0: }
michael@0: foo();