[Webkit-unassigned] [Bug 164849] New: Proxy's [[Get]] passes incorrect receiver

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=164849

            Bug ID: 164849
           Summary: Proxy's [[Get]] passes incorrect receiver
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Macintosh
                OS: OS X 10.11
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: shvaikalesh at gmail.com

Please consider the following code:

```
var target =
{
    get prop()
    {
        console.log(this == proxy) // => `false`, should be `true`
    }
}

var proxy = new Proxy(target, {})

proxy.prop
```

`proxy.prop` calls `[[Get]]` on `proxy` with `"prop"` as key and `proxy` as receiver.
Proxy's `[[Get]]` method checks for `get` trap, it is missing, so it should call `[[Get]]` on `target` with **the same** parameters.
However, JSC does not pass receiver, thus `prop` getter is called with context of `target`, not `proxy`.

Both V8 and SpiderMonkey implement this correctly.
tc39/test-262 PR: https://github.com/tc39/test262/pull/792
chai/chaijs issue: https://github.com/chaijs/chai/issues/855

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