On Tue, Jul 16, 2013 at 7:10 PM, Erik Arvidsson <erik.arvidsson at gmail.com>wrote:
> All of the new constructors, Map, Set, WeakMap and WeakSet should fail
> when called as a function unless `this` already has a certain internal
> property, ie [[MapData]]. This is so that sub classing works as
> expected.
>
> However, all JS engines that supports Map, Set and WeakMap are future
> hostile and they all return a new instance when called as a function.
> For example, here is the V8 code:
>
> function MapConstructor() {
> if (%_IsConstructCall()) {
> %MapInitialize(this);
> } else {
> return new $Map();
> }
> }
>
> I understand that fully supporting @@create requires a lot of work but
> until then we should at least throw when called as function to allow
> us to get out of this mess eventually.
>
It's painful, but I agree. This will prevent a build up of incorrect code
that may hold @@create semantics hostage.
Rick
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domenic at domenicdenicola.com (2013-07-18T16:30:55.602Z)
It's painful, but I agree. This will prevent a build up of incorrect code
that may hold @@create semantics hostage.
On Tue, Jul 16, 2013 at 7:10 PM, Erik Arvidsson <erik.arvidsson at gmail.com>wrote: > All of the new constructors, Map, Set, WeakMap and WeakSet should fail > when called as a function unless `this` already has a certain internal > property, ie [[MapData]]. This is so that sub classing works as > expected. > > However, all JS engines that supports Map, Set and WeakMap are future > hostile and they all return a new instance when called as a function. > For example, here is the V8 code: > > function MapConstructor() { > if (%_IsConstructCall()) { > %MapInitialize(this); > } else { > return new $Map(); > } > } > > I understand that fully supporting @@create requires a lot of work but > until then we should at least throw when called as function to allow > us to get out of this mess eventually. > It's painful, but I agree. This will prevent a build up of incorrect code that may hold @@create semantics hostage. Rick -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20130716/c796c8f0/attachment.html>