« Bugzilla Issues Index

#387 — [[Get]] and GetValue can return Reference Type

derived from

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.
As the result, GetValue may return Reference Type because that use result value of [[Get]]

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;


typeof obj.v

Then, typeof should treat Reference Type also, but in 11.4.3, Reference Type is not considered.

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 ways 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.

[[Call]] can no longer return a Reference.

Fixed in rev 15 draft