Making it a dynamic error at class definition time to extend null would
work but the motivation for not doing that was that someone might want to
create a class that has a {__proto__: null} prototype. Personally, I would
be fine with saying that this case is so rare that it would be better to
have that dynamic error at class definition time.On Sat Feb 14 2015 at 4:52:40 PM Mark S. Miller <[email protected]> wrote: > On Sat, Feb 14, 2015 at 1:45 PM, Axel Rauschmayer <[email protected]> > wrote: > >> >> On 14 Feb 2015, at 22:26, Mark S. Miller <[email protected]> wrote: >> >> On Sat, Feb 14, 2015 at 1:21 PM, Axel Rauschmayer <[email protected]> >> wrote: >> >>> But it’s not an error! Either of the following two classes fail later, >>> when you instantiate them, but not right away. >>> >>> ```js >>> const X = null; >>> class C extends X {} >>> >>> class D extends null {} >>> ``` >>> >> >> I didn't mean to imply an early error. The "extends X" can only produce a >> dynamic error, so I'm arguing that "extends null" should do the same. >> >> >> When I say “early”, I don’t mean “static”, I mean: dynamically, when the >> class definition is evaluated, not later when the class is instantiated via >> `new`. >> >> I’m not seeing a dynamic error in the spec when the `extends` clause is >> null (step 6e): >> https://people.mozilla.org/~jorendorff/es6-draft.html#sec-runtime-semantics-classdefinitionevaluation >> > > > That's a good suggestion. AFAICT, it would be an improvement. I don't see > any downside. > > Allen? > > > >> >> >>> Or dynamically switching from "derived" to "base" (but you seem to be >>> saying that doing this dynamically is not a good idea). >>> >> >> Dynamically switching from derived to base does not work, because our >> super semantics depends statically on the difference. >> >> >> Ah, checked statically, I wasn’t aware! Hadn’t found the check >> beforehand. Searched some more and it is indeed there, in 14.5.1. >> >> -- >> Dr. Axel Rauschmayer >> [email protected] >> rauschma.de >> >> >> >> > > > -- > Cheers, > --MarkM > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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