[Webkit-unassigned] [Bug 185211] New: JavaScriptCore should throw TypeError if [[OwnPropertyKeys]] returns duplicate entries

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=185211

            Bug ID: 185211
           Summary: JavaScriptCore should throw TypeError if
                    [[OwnPropertyKeys]] returns duplicate entries
           Product: WebKit
           Version: Safari 11
          Hardware: Unspecified
                OS: Linux
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: acsv2 at cin.ufpe.br

Hello,
according ES6 specification (https://github.com/tc39/ecma262/pull/833), the engine should throw a TypeError if ownKeys have duplicate entries.

OS = Ubuntu 17.10 x64
JavaScriptCore: 606.1.9.4

Steps to reproduce:

var proxy = new Proxy({}, {
    ownKeys: function (t) {
        return ["A", "A"];
    }
});
var keys = Object.keys(proxy);

Actual results:
Pass without failures

Expected results:
TypeError: proxy [[OwnPropertyKeys]] can't report property '"A"' more than once

Actually, only SpiderMonkey supports this specification. V8 have an open issue (https://bugs.chromium.org/p/v8/issues/detail?id=6776).

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