On Mon, Apr 20, 2015 at 12:44 PM, Allen Wirfs-Brock <[email protected]> wrote: >> In the spec, 9.1.9 step 4.d.i. is where `super.prop = 2` ends up, with >> O=X.prototype. > > 4.d.1 doesn't set the property, it just comes up with the property descriptor > to use, if the `Receiver` does not already have a corresponding own property. > > 5.c+5.e checks if the corresponding own property actually exists on the > `Receiver`. > > If it already exits then it does a [[DefineOwnProperty]] that only specifies > the `value` attribute. This should respect the current `writable` attribute > of the property and hence reject the attempt to change the value.
I agree with all of this, except I don't see where the attempt is rejected. Since the property is configurable, I think [[DefineOwnProperty]] succeeds. The property is still non-writable afterwards. Only the value changes. So this isn't breaking the object invariants: the property in question is configurable, so it's OK (I guess) to change the value. It's just surprising for assignment syntax to succeed in doing it. -j _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
