Allen Wirfs-Brock (2014-11-30T17:53:08.000Z)
d at domenic.me (2014-12-08T21:46:14.569Z)
Yes, `__proto__ : <expr>` in an object literal is a special form with different semantics than the other PropertyDefinition forms. The relaxation of the duplicate entry was explicitly not applied to it. It's worth noting that: __proto__: <expr> and ["__proto__"] : <expr> do not mean the same thing. The first form does a [[SetPrototypeOf]] and is the form that the above early error applies to. The second form does a [[DefineProperty]] and does not place any restrictions of duplicates.