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<body><span class="vcard"><a class="email" href="mailto:sbarati@apple.com" title="Saam Barati <sbarati@apple.com>"> <span class="fn">Saam Barati</span></a>
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bz_status_NEW "
title="NEW - [test262] Fixing mapped arguments object property test case"
href="https://bugs.webkit.org/show_bug.cgi?id=159398">bug 159398</a>
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<td style="text-align:right;">Attachment #291051 Flags</td>
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [test262] Fixing mapped arguments object property test case"
href="https://bugs.webkit.org/show_bug.cgi?id=159398#c73">Comment # 73</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [test262] Fixing mapped arguments object property test case"
href="https://bugs.webkit.org/show_bug.cgi?id=159398">bug 159398</a>
from <span class="vcard"><a class="email" href="mailto:sbarati@apple.com" title="Saam Barati <sbarati@apple.com>"> <span class="fn">Saam Barati</span></a>
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<pre>Comment on <span class=""><a href="attachment.cgi?id=291051&action=diff" name="attach_291051" title="Patch">attachment 291051</a> <a href="attachment.cgi?id=291051&action=edit" title="Patch">[details]</a></span>
Patch
View in context: <a href="https://bugs.webkit.org/attachment.cgi?id=291051&action=review">https://bugs.webkit.org/attachment.cgi?id=291051&action=review</a>
<span class="quote">> Source/JavaScriptCore/runtime/GenericArgumentsInlines.h:194
> + if (optionalIndex && !thisObject->isConfigurable(optionalIndex.value()) && !descriptor.justWritablePresent())</span >
I'm not sure this is correct here. I think you want to be following:
<a href="https://tc39.github.io/ecma262/#sec-validateandapplypropertydescriptor">https://tc39.github.io/ecma262/#sec-validateandapplypropertydescriptor</a>
more or less here, with some extra rules defined in:
<a href="https://tc39.github.io/ecma262/#sec-arguments-exotic-objects-defineownproperty-p-desc">https://tc39.github.io/ecma262/#sec-arguments-exotic-objects-defineownproperty-p-desc</a>
It looks like the code below falls back to normal object storage. Why not just fall back to normal object storage in every case instead of creating the isConfigurable map?
<span class="quote">> JSTests/stress/arguments-non-configurable.js:27
> +function tryChangeWritableOfNonConfigurableDescriptor(x) {
> + Object.defineProperty(arguments, 0, {configurable: false});
> + Object.defineProperty(arguments, 0, {writable: true});
> + Object.defineProperty(arguments, 0, {writable: false});
> +}</span >
This is the specified behavior? This goes against normal object behavior:
<span class="quote">>>> Object.defineProperty(o, "f", {configurable: false, value: 20})</span >
[object Object]
<span class="quote">>>> o.f</span >
20
<span class="quote">>>> o.f = 40</span >
40
<span class="quote">>>> o.f</span >
20
<span class="quote">>>> Object.defineProperty(o, "f", {writable: true, value:50})</span >
Exception: TypeError: Attempting to change writable attribute of unconfigurable property.</pre>
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