On 2015/09/08 20:41:36, caitp wrote:
On 2015/09/08 20:23:54, adamk wrote:
> I haven't looked at the patch yet (just back from vacation), but I don't
think
> we can switch from %AppendElement to simple assignment. V8 should match
the
> spec, not Babel.
>
> What do you mean by "wasn't really correct before"?
I mean, it didn't really behave correctly, in the original desugaring
version,
or in the original version.
Try http://jsfiddle.net/pkvfzubc/ in both M45 and M47 (with
--harmony-rest-parameters):
Both %AppendElement() and the old runtime approach in m45 were respecting
the
prototype chain. They didn't throw themselves, but they are not creating
the
data property when they should be.
This version would be mostly unobservable unless you do something weird
like
define accessors on Array.prototype. I've filed a bug to implement
%_CreateDataProperty() so that we can get adequate performance out of this
(and
many other areas in the spec) without doing the wrong thing
(https://code.google.com/p/v8/issues/detail?id=4414)
In the mean time, I don't think it would hurt terribly badly to make it
broken
in a subtly different way here, but with improved performance.
Actually I'm wrong, they both do seem to be creating the data property, it's
just console.log that's somehow doing the wrong thing. Something else seems
to
be broken?
https://codereview.chromium.org/1308123007/
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