Throwing when symbol *wrappers* are converted to primitives

Claude Pache claude.pache at gmail.com
Sat Dec 27 00:04:43 PST 2014


> Le 27 déc. 2014 à 08:41, Claude Pache <claude.pache at gmail.com> a écrit :
> 
> 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
> 
> —Claude

In fact, that bug was for the particular case of wrapped symbol used as property key. For the more general case of converting a Symbol wrapper object back into a primitive value, I believe that behaviour also changed during the life in the spec draft, but I am too lazy to find when. (Note that the current draft defines Symbol.prototype[@@toPrimitive], and AFAIK, V8 doesn't implement @@toPrimitive yet.)

—Claude

> 
> Le 27 déc. 2014 à 08:17, Axel Rauschmayer <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
>> 
>> -- 
>> Dr. Axel Rauschmayer
>> axel at rauschma.de
>> rauschma.de
>> 
>> 
>> 
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