[[Get]] and GetValue can return Reference Type

[Yusuke Suzuki]

Thanks, I filed this issue at
https://bugs.ecmascript.org/show_bug.cgi?id=387

Regards,
Yusuke Suzuki

On Thu, Jun 14, 2012 at 12:47 AM, Allen Wirfs-Brock
<allen at wirfs-brock.com>wrote:

> could you file this as a bug at bugs.ecmascript.org
>
> I want to make sure it isn't forgotten if nobody else responds.
>
> Allen
>
>
> On Jun 11, 2012, at 11:03 PM, Yusuke Suzuki wrote:
>
> This issue is derived from Esprima issue 81
> http://code.google.com/p/esprima/issues/detail?id=81
>
> Hello everyone,
>
> According to the ECMA262 5.1th, [[Call]] of host object may return
> Reference Type.
> So, all values using raw [[Call]] result may be Reference Type.
>
> For example, [[Get]] may return Reference Type if *getter* is a host
> object that [[Call]] returns Reference Type.
> http://ecma-international.org/ecma-262/5.1/#sec-8.12.3
> As the result, GetValue may return Reference Type because that use result
> value of [[Get]]
> http://ecma-international.org/ecma-262/5.1/#sec-8.7.1
>
> And, for example, if we define getter of object, getter function is host
> object that [[Call]] return Reference Type,
>
>     (10, obj.getter)
>
> returns Reference type, so,
>
>     (10, obj.getter) = 10;
>
> is valid because GetValue is performed, but GetValue result is also
> Reference Type.
>
> In the ECMA262 5.1th, GetValue is assumed that doesn't return Reference
> Type, for exmaple,
>
>     var obj = {
>         get v() {
>            // this v function is host object and returns Reference;
>            // we can define this v using host object and defineProperty
>            return Reference;
>         }
>     };
>
> And,
>
>     typeof obj.v
>
> Then, typeof should treat Reference Type also, but in 11.4.3, Reference
> Type is not considered.
> http://ecma-international.org/ecma-262/5.1/#sec-11.4.3
>
> I think this is a bug of spec and GetValue and [[Get]] should not return
> Reference type, is it right?
>
> To fix this, I think following 3 way are good.
>
>    1. perform GetValue on [[Call]] result in the spec
>    2. re-define [[Get]] and GetValue can return Reference Type. This
>    needs to re-define all the spec part using [[Get]], GetValue and others
>    3. remove feature that [[Call]] can return Reference Type
>
> Because all modern engines don't consider that [[Call]] result is
> Reference and this feature makes big performance-regression, personally I
> think 3 is better.
>
> Regards,
> Yusuke Suzuki
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>
>
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