Bug 155012 – [[Set]] isn't correct with respect to the spec and Proxy

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Saam Barati]

When we traverse the prototype chain during [[Set]], we need to perform the following if O is a proxy
because this is observable behavior.
```
if (O is a proxy) {
    let result = O.[[GetOwnPropertyDescriptor]](...)
    if (result) return;
    let proto = O.[[GetPrototypeOf]]()
...
}
```
Right now, we just perform the [[Set]] unconditionally.
We can special case Proxy here because this behavior is only observable with a Proxy.
If the thing isn't a Proxy, we can do the fast prototype() lookup, etc.

[Alexey Shvayka]

Created attachment 382766 [details]
Patch

[Saam Barati]

Comment on attachment 382766 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=382766&action=review

> Source/JavaScriptCore/runtime/JSObject.cpp:-843
> -            // https://bugs.webkit.org/show_bug.cgi?id=155012

can you close this bug?

[Alexey Shvayka]

(In reply to Saam Barati from comment #2)
> Comment on attachment 382766 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=382766&action=review
> 
> > Source/JavaScriptCore/runtime/JSObject.cpp:-843
> > -            // https://bugs.webkit.org/show_bug.cgi?id=155012
> 
> can you close this bug?

It is this very bug, so the commit bot will close it (I don't have such rights yet).

[Saam Barati]

(In reply to Alexey Shvayka from comment #3)
> (In reply to Saam Barati from comment #2)
> > Comment on attachment 382766 [details]
> > Patch
> > 
> > View in context:
> > https://bugs.webkit.org/attachment.cgi?id=382766&action=review
> > 
> > > Source/JavaScriptCore/runtime/JSObject.cpp:-843
> > > -            // https://bugs.webkit.org/show_bug.cgi?id=155012
> > 
> > can you close this bug?
> 
> It is this very bug, so the commit bot will close it (I don't have such
> rights yet).

haha. Oops. I didn't realize it was the same one :-)

[WebKit Commit Bot]

Comment on attachment 382766 [details]
Patch

Clearing flags on attachment: 382766

Committed r252019: <https://trac.webkit.org/changeset/252019>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/56883293>