Static Array and String Generics and Host Objects (ATTN IE Team)

Mark S. Miller erights at
Mon Dec 7 14:50:00 PST 2009

On Mon, Dec 7, 2009 at 11:40 AM, Maciej Stachowiak <mjs at> wrote:
> On Dec 4, 2009, at 1:48 PM, Garrett Smith wrote:
>> Static Array and String Generics was an ES4 proposal[0], and is
>> implemented in Mozilla JavaScript 1.6[1].

Note that the function generics on that page[0] break Liskov
substitutability, since the Function constructor is itself a function
inheriting from Function.prototype. Thus, Function.apply overrides
Function.prototype.apply while implementing an incompatible contract.

>> What are the plans for including Array and String Generics in future
>> revision of ES?
> I'm curious about this as well. We've had some requests to add these to
> JavaScriptCore. I'd like to know if they were explicitly rejected from
> standard ECMAScript, or might be considered for further ECMAScript editions.

They were explicitly rejected for ES5, but more by way of postponing
the issue rather than rejecting them for the future. They may indeed
be considered for ES-Future.

> Would the ECMAScript standards community advise that we implement these in
> WebKit or hold off?

I would recommend holding off. IMO, their extra convenience does not
pay for the added complexity.


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