why can't default members be forward-declared

[gavinking]

The spec says that default attributes and functions can't be forward-declared, and the typechecker enforces that, but for the life of me I don't remember why. It doesn't seem like a reasonable restriction.

[gavinking]

I have pushed a commit that relaxes the restriction. But is there some reason we need it?

[gavinking]

But is there some reason we need it?

Yes: see #1413.