Domenic Denicola wrote:
From: Brendan Eich [mailto:[email protected]]
> Can we get a leg up, rather than wait for a f2f? This thread seems fine for
further discussion and simplifying proposals.
Well, to be clear, I'd prefer we not change anything at all. It's too late to
be tweaking something that's been set in the spec for a very long time now.
But it appears that we have some relitigation on this particular topic [on the
agenda anyway][1]:
Toxic terms like "relitigation", heard it from from RealAlexRussell and
it sucked then too, are out of line -- we are not lawyers. Also, new
TC39 rep Jordan Harband of Twitter raised this at the last meeting,
asked Allen about working on it, got a green light.
> @@toStringTag (rationales) (Jordan Harband)
>
> - Missing unspoofable builtin values (Math, JSON, Object): spec bug
> - Should built-in @@toStringTag values have { configurable: false }?
> - Should Object.prototype.toString add a prefix to all non-built-in
@@toStringTag values?
It seems the "protections" in the spec so far have given some the misleading
impression that we want to encourage O.p.toString as an unspoofable [[Class]] test. (Not
that [[Class]] even exists anymore!) But as Allen points out, that's not the idea at all.
And I'm loathe to perpetuate that usage of them---or even the impression that they should
be used that way. (Nominal-typing bad!
That "X-typing bad!" line is not helpful. (What is this, a sports/beer
commercial?)
Even structural typing fans such as Mark Miller have noted in their
research results the benefits of nominal types for certain use-cases.
Sometimes you need to know your implementation. This is the exception to
the rule, but it's not always and everywhere "bad!".
Especially in ES6/ES7/etc. where proxies/value types/etc. give us the ability
to perfectly emulate the characteristics of those types!)
Yes, we want to complete the MOP so nominal types are equivalent to
branded structural types, a la Modula 3, and per David Ungar's position
articulated many times over the years (I heard David say it to Tom Van
Cutsem in person at SPLASH 2011, re: Proxies not interceding fully for
all types). But we aren't there yet.
Anyway, this has little to do with getting the details of toStringTag in
the best shape we can for ES6. Perhaps Jordan will weigh in, but in any
case, I found his links and questions from the agenda helpful -- others
may too. Here they are:
1.
https://github.com/ljharb/agendas/wiki/January-TC39-@@toStringTag-discussion
2. https://bugs.ecmascript.org/show_bug.cgi?id=3506
3. Should built-in `@@toStringTag` values have `{ configurable: false }`?
4. Should `Object.prototype.toString` add a prefix to *all* non-built-in
`@@toStringTag` values?
/be
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