maplike handling is really weird

[bzbarsky]

There are various parts of this spec that attempt to define what the "map entries" are for maplikes in terms of a Map. But maplikes already have a Map whose [[MapData]] is defined to be the "map entries". See https://heycam.github.io/webidl/#es-maplike

So whatever you're doing with [[data]] right now should instead be done by manipulating the [[BackingMap]], I would think. And you need to specify exactly how you manipulate it, of course.

[jyasskin]

I don't know why I missed the [[BackingMap]] object that's available for this. Fix coming up.

[jyasskin]

Oh, maybe I was trying to specify against the language-independent maplike spec, which says that "Prose accompanying the interface can describe how the map entries of an object change.", instead of the ES binding, which provides [[BackingMap]]. I'll still send the change to use the ES-specific slots, since I'm assuming ES elsewhere.

[bzbarsky]

You skipped the "you need to specify exactly how you manipulate it, of course" bit. Filed #351 on that, I guess...