[Haskell] Empty instance declaration

[Ralf Laemmel]

> You did not say anything that's imprecise about "mentioning each other
> in a cycle", just the well-known fact that it's not equivalent to total
> termination checking (in fact, it's neither fully an overestimate nor
> underestimate of termination -- it's just an estimate that's likely to
> be right when used in the context of default method definitions).

It's imprecise also in so far that you would need to define what you mean by it.
Does it mean that we focus on the "pattern"

f ... = g ...
g ... = f ...

... or does it include the case

f ... = h g ...
g ... = f ...

... and that's still very imprecise because the dots don't mean anything proper.

Are you willing to look at the pattern *after* overloading resolution.

Let's have a proper termination checker!

Btw, obviously a class by itself would not be checked (in terms of the
default methods), but only an instance (with the defaults pulled in).

Cheers,
Ralf