On 15 February 2014 06:10, Brendan Eich <brendan at mozilla.com> wrote:
> Allen Wirfs-Brock wrote:
>>
>> On Feb 14, 2014, at 11:38 AM, Jeremy Martin wrote:
>>
>>> >  On further reflection, #3 does feel like trying to rewrite the past.
>>> > For better or worse, non-strict mode allows declarations to persist past the
>>> > eval().  And while strict mode provides a license-to-kill on behavior like
>>> > that, I don't really see strong justification for that kind of surprise
>>> > factor for let in non-strict mode.
>>> >  >  If you're not using strict mode AND you're using eval(), the damage
>>> > is arguably already done (or at least the danger already exists).  Changing
>>> > the behavior of let in this case feels like removing an arbitrary* foot-gun
>>> > when we're already in the armory, so to speak.
>>> >  >  * Granted it's not completely arbitrary, since `let` is new whereas
>>> > `var` is not, but hopefully you get my point.
>>
>>
>> Another consideration in the back of my mind is that there may be useful
>> to implementors to knowing that let/const/class declaration are never
>> dynamically added to a non-global environment.
>
> +lots, this should be front of mind.
>
> In a block, we want the bindings local to that block to be statically
> analyzable. We want no non-local mode effects. So, #3 still wins.

Strongly seconded.

/Andreas

Strongly seconded.