[dllthomas]

Certainly the larger an interface is, the less likely that someone supports all of it by accident. Of course, that's both good and bad - if the accidental support would have been correct then we're missing out, but I think most of the time we shouldn't count on that.

One could possibly force the issue by including an unused function with a deliberately unique name (supports_interface_foo, or maybe a UUID or both) as part of the interface. Can functions added later fill parts of interfaces? If so, this approach would make the situation roughly that of Haskell typeclasses. If not, then this approach makes the situation roughly that of Java interfaces. In either case, it might be appropriate to some pickier interfaces.