ExtendableMessageEvent.source cannot be SameObject

[ehsan]

According to WebIDL, [SameObject] doesn't apply to union types, so we should remove this annotation from ExtendableMessageEvent.source.

[jungkees]

The [SameObject] extended attribute must not be used on anything other than a read only attribute whose type is an interface type or object. (WebIDL 4.3.15 [SameObject])

Did you reference this part? Before removing it, I just want to make sure whether it intends to disallow the case when all the member types of the union are interface types.

/cc @heycam @bzbarsky

[bzbarsky]

That part of the IDL spec is just bogus, imo; there are existing IDL issues on that. Any type that's always an object, including unions of interface types, Promise, etc, should be OK to use with [SameObject].

Arguably, even a union for which some types are an object should be OK with [SameObject].

@heycam may have pointers to the IDL spec issues off the top of his head.

[jungkees]

Sounds reasonable. I found the IDL spec issue for this: whatwg/webidl#71

[jakearchibald]

Pre F2F notes: Doesn't look like there's anything to discuss

[jungkees]

Closing waiting on the IDL issue.