Definition of "is an array index" makes "-0" an array index

[foolip]

https://heycam.github.io/webidl/#dfn-array-index-property-name

This links to https://tc39.github.io/ecma262/#sec-canonicalnumericindexstring which special-cases "-0".

This problem was introduced with #427, the previous definition was OK:
https://web.archive.org/web/20170903233050/heycam.github.io/webidl/#dfn-array-index-property-name

If the current definition were used, it would mean that document.all["-0"] should behave like document.all["0"], which it doesn't as implemented.

[foolip]

@TimothyGu can you take a look?

[TimothyGu]

I'm inclined to just say "If P is an array index" as ES does it, but since that's not preferred here just adding a "-0" as an early return is fine.

[annevk]

Well, this affects more than just document.all, right? I think we very much want the Ecma array index definition for other indexed getters...

[foolip]

Yes, it affects more things, and I don't think @TimothyGu was suggested a document.all-specific workaround.