On 4/13/2013 12:31 AM, Andreas Rossberg wrote:
On 13 April 2013 00:12, Brandon Benvie <[email protected]> wrote:
3.) A new type of primitive along with a new type of wrapper. In this case
we use the String/Number/Boolean precedent where `Symbol()` and `new
Symbol()` produce different kinds of results. The problem here is the
confusion that comes with ToString/ToPropertyKey when called on a Symbol
wrapper. What does `obj[new Symbol] = 5` do, for example? It allows footguns
like `obj[key + '_ext']` to silently do the wrong thing.
That was the consensus at the last meeting, and it's already
implemented in V8. The decision included that
Symbol.prototype.toString is poisoned, i.e., any attempt to implicitly
convert a symbol or a wrapped symbol to a string will throw, including
both of your examples. So no footgun, which I agree is important.
(Object.prototype.toString is not on that path, however, so can treat
symbols separately.)
I'm a bit confused about some bits of Allen's comment on your Gist,
though, which don't line up with what I thought we decided on. In
particular, ToObject(symbol) should be perfectly fine and creates a
wrapper object. Similarly, Symbol()["foo"] auto-converts to a wrapper
object and returns undefined as usual, and new Symbol() directly
creates a wrapper object.
/Andreas
This would be the reason I created this thread: there was at least two
different interpretations of the outcome of the meeting by people who
were at the meeting, and a third one (mine) that came from reading the
meeting notes. From that I surmised it would be good to, at the very
least, figure out which one of the three is an accurate reflection of
what was actually to be the final version.
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