Shadowing a Window property on the global object yields undefined

[kmcallister]

$ ./servo ../src/test/html/test_bindings.html
ALERT: [object Window]
ALERT: ==1==
~"Error at file:/home/keegan/proj/servo/servo/build/../src/test/html/test_bindings.js:6u32: TypeError: document is undefined\n"

[jdm]

I suspect that's actually bareword document, not window.document. Still, both should work...

[kmcallister]

The offending code is

var document = window.document;
window.alert(document.documentElement);

If I alert(window.document) I get undefined.

[jdm]

[00:22:53] <jdm> what's supposed to happen if I use |var document = window.document; alert(document);|?
[00:23:10] <jdm> this has come up in servo and document and window.document seem to be undefined for some reason
[00:23:24] <Waldo> if document is a getter/setter own property on window, then that should be an early TypeError
[00:23:46] <jdm> it's an own property on window's prototype
[00:23:53] <Waldo> if it's a getter/setter on Window.prototype, or some other prototypal thing, then it should do alert(undefined)
[00:24:05] <jdm> huh
[00:24:08] <Waldo> which I think might alert the empty string because ha, ha, ha
[00:24:14] <jdm> that sounds like it's working, I guess

[bzbarsky]

Two things:

1. Per spec, window.document is unforgeable, so an own property of the window.
2. Per spec proposals, all of the global's stuff lives directly on the global, not on the proto chain.

#2, precisely because of this shadowing issue.