michael@0: load(libdir + "asserts.js");
michael@0: 
michael@0: /*
michael@0:  * Throw a TypeError if the trap skips an existing own enumerable property on a
michael@0:  * non-extensible object
michael@0:  */
michael@0: var target = {};
michael@0: Object.defineProperty(target, 'foo', {
michael@0:     enumerable: true,
michael@0:     configurable: true
michael@0: });
michael@0: Object.preventExtensions(target);
michael@0: assertThrowsInstanceOf(function () {
michael@0:     Object.keys(new Proxy(target, {
michael@0:         keys: function (target) {
michael@0:             return [];
michael@0:         }
michael@0:     }));
michael@0: }, TypeError);