On dropping @names

Brendan Eich brendan at mozilla.com
Fri Dec 28 12:05:48 PST 2012

David Herman wrote:
>> >  For the first group (function, module), there is no problem. For the second (let, const, class, private -- although TBH, I forgot the reason why 'class' is in this group), we have temporal dead zone, where accessing a variable before its initialization is an error.
> The class's `extends` clause has to be evaluated and can have arbitrary user code, side effects, etc.

Oops, forgot that! Good point.

>   Similar for possible future clauses like computed property value expressions.
And static fields with initializers.

>> >  That seems clean, useful, consistent, and fairly easy to understand. Introducing extra rules for 'let'? Not so much.
> But TDZ does introduce extra rules! Especially with disallowing assignment temporally before initialization.

Wait, Andreas was stipulating TDZ with its extra rules but noting they 
apply to non-function, non-module binding forms. So apples to apples, he 
is noting that if let lacks TDZ, then we have something extra.

You could counter-argue that this something extra is already in the pot 
due to var.

I'm still ok with TDZ, but apprehensive of performance fault myth and 
truth based on early implementations of it that are not sufficiently 
optimized (if only for gamed benchmarks).


More information about the es-discuss mailing list