The fact that [[writable]] can change for a non-configurable property is definitely intentional, see the state diagram MarkM once put up at < http://wiki.ecmascript.org/doku.php?id=es3.1:attribute_states&s=diagram>.
Cheers, Tom 2013/6/10 Axel Rauschmayer <[email protected]> > The ECMAScript 5.1 spec says (8.6.1): > [[Configurable]]: If false, attempts to delete the property, change the > property to be an accessor property, or change its attributes (other than > [[Value]]) will fail. > > On the other hand [[DefineOwnProperty]] (8.12.9) allows one to change > writability from true to false, even if a property is not configurable: > > 10 Else, if IsDataDescriptor(current) and IsDataDescriptor(Desc) are > both true, then > a. If the [[Configurable]] field of current is false, then > i. Reject, if the [[Writable]] field of current is false and the > [[Writable]] field of Desc is true. > ii. If the [[Writable]] field of current is false, then > 1. Reject, if the [[Value]] field of Desc is present > and SameValue(Desc.[[Value]], current.[[Value]]) is false. > b. else, the [[Configurable]] field of current is true, so any change is > acceptable. > > (10.a) seems to ignore the case of [[Writable]] of `current` being true. > Is this deliberate? > > Should the description of [[Configurable]] be changed to better reflect > the status quo? > > -- > Dr. Axel Rauschmayer > [email protected] > > home: rauschma.de > twitter: twitter.com/rauschma > blog: 2ality.com > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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