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#1445 — Coverage: 12.6.4 Non-enumerable property shadows enumerable one.

• bug_id: 1445
• creation_ts: 2013-04-16 10:10:00 -0700
• short_desc: Coverage: 12.6.4 Non-enumerable property shadows enumerable one.
• delta_ts: 2014-09-20 12:52:06 -0700
• product: Test262
• component: ECMA-262 Tests
• version: unspecified
• rep_platform: All
• op_sys: All
• bug_status: IN_PROGRESS
• priority: Normal
• bug_severity: enhancement
• everconfirmed: true
• reporter: Gareth Smith
• assigned_to: Brent Baker
• cc: ["princexcess69", "trbaker"]

---

• commentid: 3646
• comment_count: 0
• who: Gareth Smith
• bug_when: 2013-04-16 10:10:51 -0700

There seem to be no tests which cover the bug reported here in V8 and WebKit:

http://code.google.com/p/v8/issues/detail?id=705
https://bugs.webkit.org/show_bug.cgi?id=38970

The issue is that if a non-enumerable property shadows an enumerable property, for-in should not enumerate it.

Would the following do?

function testcase() {
var proto = {prop:"inheritedValue"};

var ConstructFun = function () { };
ConstructFun.prototype = proto;

var child = new ConstructFun();
Object.defineProperty(child, "prop", {
value: "overriddenValue",
enumerable: false,
configurable: true,
writable: true
});

var numVisibleProperties = 0;
for (var k in child) {
numVisibleProperties++;
}

return numVisibleProperties === 0;
}

runTestCase(testcase);

---

• commentid: 3668
• comment_count: 1
• who: Gareth Smith
• bug_when: 2013-04-26 01:31:59 -0700

As discussed on-list[1], here is a better version of this test:

function testcase() {
var proto = {prop:"inheritedValue"};

var ConstructFun = function () { };
ConstructFun.prototype = proto;

var child = new ConstructFun();
Object.defineProperty(child, "prop", {
value: "overriddenValue",
enumerable: false,
configurable: true,
writable: true
});

for (var k in child) {
if(k==="prop") {
return false; // prop is shadowed by a non-enumerable property.
}
}
return true; // We didn't see the non-enumerable 'prop'.
}




[1] https://mail.mozilla.org/pipermail/test262-discuss/2013-April/000180.html