get/setIntegrity trap (Was: A case for removing the seal/freeze/isSealed/isFrozen traps)

Tom Van Cutsem at
Mon Mar 18 08:49:59 PDT 2013

Ok, somehow I had completely missed "9.3.10 TestIntegrityLevel (O, level)"
which does exactly the derived computation for sealed and frozen objects.

I think André is right though about the bug in 8.3.3 step 2.a.


2013/3/17 Allen Wirfs-Brock <allen at>

> Tom recently suggested that that we really don't need MOP-level or trap
> operations from freezing, sealing and testing those states.  Also, there
> seems to be minimal support for having explicit freeze/sealed integrity
> states or for adding integrity integrity states.  So I'm probably going to
> go make to an style design.  We'll only have [[IsExtensible]] and
> [[PreventExtensions]] MOP/trap/Reflect operations.
>  Object.freeze/seal/isFrozen/isSealed will be derived operations.
> Allen
> On Mar 17, 2013, at 10:16 AM, Tom Van Cutsem wrote:
> Hi,
> Allen's latest draft (Rev. 14) contains the change where
> [[Freeze]],[[Seal]] and [[PreventExtensions]] have been consolidated into
> [[HasIntegrity]]/[[SetIntegrity]]. While no changes were made to the Proxy
> API (i.e. no has/getIntegrity traps yet), the definition of
> Object.{freeze,seal,preventExtensions} did change, and this is sufficient
> to expose an incompatibility with ES5, namely:
> Object.isFrozen(Object.preventExtensions({})) // true in ES5, false in ES6
> Rev14 draft
> I still feel like the consolidation isn't worth this incompatibility.
>  Allen, could you clarify what your intent is? Is it your intent that
> this incompatibility will be fixed with further spec changes?
> Cheers,
> Tom
> 2013/2/21 Brendan Eich <brendan at>
>> Tom Van Cutsem wrote:
>>> That said, I don't think this is enough evidence either for or against
>>> the breaking change.
>> I have a hard time believing we can break ES5. It has been shipping for
>> years (plural, at least in one case) in major browsers that evergreen their
>> user bases.
>> /be
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