Array.prototype.concat with Proxy

[Pierre-Marie Dartus]

**Step to reproduce:**
const proxy = new Proxy([3, 4], {});
const res = [1, 2].concat(proxy);

console.log(res[0]);
console.log(res[1]);
console.log(res[2]);
console.log(res[3]);

**Expected output:**
1
2
3
4

**Actual output:**
1
2
Proxy {0: 3, 1: 4}
undefined

**Observation:**
Works in Chrome 65 and Firefox 58

[Radar WebKit Bug Importer]

<rdar://problem/39256680>

[Caitlin Potter (:caitp)]

Created attachment 341460 [details]
Patch

[Saam Barati]

Comment on attachment 341460 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=341460&action=review

> Source/JavaScriptCore/ChangeLog:11
> +        This incorrectly treated prevented Proxy objects from being spread when

“treated prevented” => prevented

> Source/JavaScriptCore/ChangeLog:12
> +        they were the only argument passed to A.p.concat(), violating ECMA-262.

Nit: I’d just spell out Array.prototype.concat

> JSTests/ChangeLog:8
> +        Before this patch, the fast case for Array.prototype.concat was taken if

Don’t think you need to repeat the same text in this changelog here

[Caitlin Potter (:caitp)]

Created attachment 341489 [details]
Patch for landing

[Caitlin Potter (:caitp)]

Comment on attachment 341489 [details]
Patch for landing

I think this patch is still slightly wrong, going to verify a bit..

[Caitlin Potter (:caitp)]

Comment on attachment 341489 [details]
Patch for landing

nevermind, I guess it was ok after all..

[WebKit Commit Bot]

Comment on attachment 341489 [details]
Patch for landing

Clearing flags on attachment: 341489

Committed r232261: <https://trac.webkit.org/changeset/232261>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Caitlin Potter (:caitp)]

Reopening to attach new patch.

[Caitlin Potter (:caitp)]

Created attachment 341520 [details]
Patch

[Caitlin Potter (:caitp)]

I didn't know we had a new test262 runner in the tree. This patch fixed some failures, so here's another patch to fix the test262 expectations.

[Saam Barati]

Comment on attachment 341520 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=341520&action=review

> JSTests/ChangeLog:3
> +
> +

Only need one new line here

[Caitlin Potter (:caitp)]

Created attachment 341538 [details]
Patch for landing

[WebKit Commit Bot]

Comment on attachment 341538 [details]
Patch for landing

Clearing flags on attachment: 341538

Committed r232282: <https://trac.webkit.org/changeset/232282>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Alexey Shvayka]

*** Bug 186991 has been marked as a duplicate of this bug. ***

[Alexey Shvayka]

*** Bug 186993 has been marked as a duplicate of this bug. ***

[Alexey Shvayka]

*** Bug 186992 has been marked as a duplicate of this bug. ***