WindowProxy [[Set]] doesn't quite make sense

[bzbarsky]

In the same-origin case, https://html.spec.whatwg.org/multipage/window-object.html#windowproxy-set does:

OrdinarySet(W, this, Receiver)

but https://tc39.github.io/ecma262/#sec-ordinaryset takes 4 arguments: An object, a property name, a property value, and a receiver.

Presumably this should be:

OrdinarySet(this, P, V, W)

or

OrdinarySet(W, P, V, Receiver)

or something? What if Receiver == this? Should we unwrap it to the Window in that case?

@domenic @annevk

[annevk]

I would expect OrdinarySet(this, P, V, Receiver) for consistency with [[Get]], but I have to admit I never quite understood what a Receiver is. I just passed it on, hoping someone else would catch it if that was wrong. I regret that error.

[annevk]

It seems with Reflect.get() you can basically specify an arbitrary Receiver.

[bzbarsky]

The reason Receiver exists in general is to handle cases where the object involved is on the proto chain of some other object.

So in our case, if you do var obj = Object.create(ourWindow) and then do a set on obj, Receiver can be obj (depending on exactly how things are donw) while this is ourWindow.

And yes, with Reflect the receiver can be pretty arbitrary.

[annevk]

For anyone looking at this in the future, we determined Receiver being allowed to be arbitrary as acceptable, given that IDL performs brand checks.