ES6 doesn't need opt-in

Mark S. Miller erights at
Wed Jan 4 08:44:53 PST 2012

On Wed, Jan 4, 2012 at 8:39 AM, Mark S. Miller <erights at> wrote:

> On Wed, Jan 4, 2012 at 4:23 AM, Andreas Rossberg <rossberg at>wrote:
>> [...]

> Here's an interesting compromise I consider perfectly reasonable. We don't
> *mandate* any ES6 code features be available in ES6 non-strict mode. But we
> don't prohibit them either. For any ES6 features that have no dependence on
> mode, like destructuring, we mandate that they be present in strict code,
> and we make them normative optional (the new Appendix B category) in
> non-strict code. Implementors are free to implement them or not in
> non-strict mode, but if they implement them, it must mean the same thing as
> the mandated meaning in strict code.

Except for nested named function definitions, which already have bizarre de
facto behaviors in non-strict code that no one can fix. Perhaps there are
more such conflicts in legacy non-standard features? If so, we probably
need to exempt them as well.

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