Enhanced Enums -- use cases

[Brian Goetz]

> I have examined the uses of Enum in our codebase as best I can. I
> remain skeptical that this feature adds enough value, although the
> ability to use different generic types on each instance would no doubt
> be useful on occasion.

Thanks for your thoughts, Stephen.

The tricky thing about evaluating this feature is that it is more likely 
to apply to classes that might like to be enums, but can't currently, 
rather than those that already fit within the constraints of enums.  
That means the examples are harder to find. Subjectively, I know that I 
have encountered that feeling of "GRRR, have to refactor this enum to 
classes" when I crossed the line.  Of course, this feature won't even 
address all of those -- but it will address some.

> What is annoying about the current implementations is the ceremony of
> setting up per instance data.

Good point.  This interacts nicely with the planned "data class" 
feature; seems likely we can dish some of those goodies to enums at the 
same time.