651971 - Is JSON prototype established correctly? (Do we care?)

Status: RESOLVED INVALID

(Tamarin Graveyard :: Library, defect, P3)

Description

[Felix S. Klock II [:pnkfelix, :fklock]]

In Lars's AS3 implementation of JSON (Bug 584704), he left a note:

    // FIXME: Spec requires that JSON's [[Prototype]] is
    // Object.prototype; but is it?  Investigate.

I'm relatively ignorant of ECMAscript at this level of detail.  I'm not sure how I would observe the [[Prototype]] of JSON, or ensure that it is Object.prototype (if that is in fact what is entailed by the ECMA standard, or if instead Lars should be referring to Object's [[Prototype]] rather than Object.prototype.  Are the two synonymous?  Is ECMA not talking about Object's [[Prototype]] when it says "the standard built-in Object prototype object (15.2.4)"?  I suppose it might not be.

Anyway I don't have time at the minute to resolve the question but I do want to and hope to today or tomorrow.

Comment 1

[Lars T Hansen]

The [[Prototype]] of the JSON object, if JSON is implemented as an AS3 class, is not going to be Object.prototype, but an object that is the "prototype" (sic!) property of the unnamed metaclass for the JSON object.  In turn, the [[Prototype]] object of that object is going to be the initial value of Class.prototype.  This is observable, consider this, which prints "fnord":

  class C {}
  Class.prototype.toString = "fnord";
  print(C.toString);

That it is so is a fact of life for AS3, and this behavior is evident elsewhere too, for example, normally Date's [[Prototype]] property delegates to Object.prototype, but in AS3 it delegates to Class.prototype first.

I would close the present bug as "not a bug".

Comment 2

[Felix S. Klock II [:pnkfelix, :fklock]]

closing as "not a bug", or closest resolution detail string thereof.