Feedback on "Read-only Override Prohibition is [not a mistake]"

Mark S. Miller erights at
Sun Jan 15 16:51:45 PST 2012

On Sun, Jan 15, 2012 at 3:02 PM, David Bruant <bruant.d at> wrote:

> So in the "2", we have:
> IE8, Firefox 9->12, Opera 11.60, 12
> and on the side of "3", we have:
> Chrome 16, Safari 5 and Safari 5.1
> Anyway, it seems that the divergence toward this aspect of the spec was
> probably there even before ES5. If no one complained about it for years it
> seems to indicate that there is room to change the spec without breaking
> content, since content does not seem to rely on the spec behavior, even if
> it was there since ES1.

I hear from the v8 team that v8 had the current non-standard (and IMO more
sensible) behavior back in the ES3 days, and no one noticed. I suspect this
was true of Safari as well but have not checked. Chrome + Safari form a
large enough share of browsers that the "no one noticed" reaction seems
like rather solid evidence to me. We have made other technically
non-backward compatible changes from previous specs on web-compat evidence
far weaker than this -- and been bitten by very few of these.

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