On 2015/03/04 15:24:09, Dmitry Lomov (chromium) wrote:
On 2015/03/04 14:44:11, caitp wrote:
> So Runtime_NewObjectHelper creates an object using the initial map of
whatever
> the constructor was, and then __maybe__ sets __proto__ to the prototype
of
the
> original constructor. That doesn't seem right to me, but I'm sure there
are
good
> reasons for doing this, maybe it's okay to leave it as-is for now?
This is absolutely correct.
Reflect.construct(Array, [], C)
invokes Array.[[Construct]] trap with [] for argumentsList and C for new
Target.
For Arrays this constructs an exotic object (Array) with __proto__ being
C.prototype.
This is what your CL does
Right, but the actual behaviour is not quite correct.
Here's a sample run:
```
(lldb) r --harmony-reflect
Process 17689 launched: '/Users/caitp/google/v8/out/x64.debug/d8' (x86_64)
V8 version 4.3.0 (candidate) [console: dumb]
d8> function A() {}
undefined
d8> function B() {}
undefined
d8> B.prototype.name = "B"
"B"
d8> Reflect.construct(A, [], B).name
"B"
d8> Reflect.construct(A, [], B) instanceof B
true
d8> Reflect.construct(A, [], B) instanceof A
false
d8> function C() {}
undefined
d8> Reflect.construct(A, [], C) instanceof A
true
d8> Reflect.construct(A, [], C) instanceof C
false
d8>
```
Notice that if I add a property to B's prototype, then we take the path
where we
do set the prototype to the right value. However, when newTarget is `C`,
which
has not touched its prototype at all, the prototype is incorrect.
https://codereview.chromium.org/913073003/
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