ProtoObject and comparison for equality and ordering

[Adam D. Ruppe]

On Wednesday, 15 May 2019 at 00:54:20 UTC, Andrei Alexandrescu 
wrote:
> The nice thing is if we opt for a statically-checked solution 
> the user will be able to make a decision on the signature of 
> opCmp in their base class, and then go with it. Different 
> hierarchies may even support different flavors of comparisons.

Yes, I agree with this.

I think the opCmp discussion should be moot, as a ProtoObject 
should not be comparable anyway; it'd simply be a compile error 
to try. Just like with trying to call any other method on it, you 
need to explicitly cast it to some interface you've defined first.