Throwing when symbol *wrappers* are converted to primitives

Axel Rauschmayer axel at rauschma.de
Fri Dec 26 23:57:52 PST 2014


Interesting, thanks! Can you explain the rationale behind that decision? To me, it seems like V8’s behavior is preferable – if I accidentally created instances of `Symbol`, I would want to get errors as early as possible.


> On 27 Dec 2014, at 08:41, Claude Pache <claude.pache at gmail.com> wrote:
> 
> I guess that V8 follows an old version of the spec draft. That particular behaviour was modified in Rev 28. See:
> 
> https://bugs.ecmascript.org/show_bug.cgi?id=3252 <https://bugs.ecmascript.org/show_bug.cgi?id=3252>
> 
> —Claude
> 
> Le 27 déc. 2014 à 08:17, Axel Rauschmayer <axel at rauschma.de <mailto:axel at rauschma.de>> a écrit :
> 
>> This is current V8 behavior:
>> 
>> ```
>> > let obj = {};
>> > obj[Object(Symbol())] = true;
>> TypeError: Cannot convert object to primitive value
>> 
>> > '' + Object(Symbol())
>> TypeError: Cannot convert a Symbol wrapper object to a primitive value
>> ```
>> 
>> Both exceptions make a lot of sense, but I don’t see that in the spec. The way I’d expect it to happen is via `Symbol.prototype[@@toPrimitive]` – it would always throw. But that’s not the case.
>> 
>> https://people.mozilla.org/~jorendorff/es6-draft.html#sec-symbol.prototype-@@toprimitive <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-symbol.prototype-@@toprimitive>
-- 
Dr. Axel Rauschmayer
axel at rauschma.de
rauschma.de



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