On Tue, Feb 10, 2009 at 2:49 PM, Allen Wirfs-Brock < [email protected]> wrote:
> I guess it is time for one of my alternative lists. Good. Thanks! > The original question was what if any restrictions should ES3.1 place upon > host objects' [[Class]] values. The alternatives on the table are: > > 1) An implementation can give any host object any [[Class]] value it wants, > including value that have specified meanings within the spec. This is what > ES3 says. > 2) An implementation may not use any of the specified [[Class]] values for > a host object. > 2a) An implementation may only use the specified [[Class]] values for a > host object that is a fully conforming implement of a Section 15 object. > (in which case, it is probably really a native object and not a host object > at all). > 3) An implementation may only use the specified [[Class]] values for host > objects that conform to some specified set of invariants that ES3.1 > specifies for each such [[Class]] value. > > #1 is what we have now with ES3 and at least some of us want to tighten the > specification because it currently means when in the presence of host > objects that testing [[Class]] guarantees nothing. > > #2 seem nice and simple to me but may not be a good fit with existing > implementations and probably requires rethinking of [[Class]]=="Function" > predicates in the Function.prototype.bind algorithm. > #2a ultimately seem the same as #2 > > #3 would be fine but requires work. We would need to decide on the > invariants for specified [[Class]] value. Yes, I am in favor of #2. > > (parting shot, if [[Class]] was really called [[ToStringIdentifier]] would > we even be having this conversation?) > > Yes, but we may have then made the (IMO) mistake of introducing a new internal unforgeable nominal type property, such as your earlier [[IsArray]], but applicable as well to at least Date, RegExp, and Function, without noticing the unfortunate redundancy with the existing unforgeable [[ToStringIdentifier]] property. -- Text by me above is hereby placed in the public domain Cheers, --MarkM
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