[Evaluation] Autocompute 'NumberOfStepCounters'

[effectfully]

This makes it so that we no longer need to update NumberOfStepCounters, it'll be updated increased automatically when a new constructor is added to StepKind.

[kwxm]

This looks OK to me. It should certainly avoid the problem that we had before.

[kwxm]

I was going to suggest that we should put this somewhere else since it's not very Cek-specific, but I don't know where would be a sensible place for it. Maybe StepCounter.hs?

[effectfully]

I'd like to keep it in there in case the structure of StepKind somehow changes. Like, what if it becomes parameterized for whatever reason? Currently it's written specifically with the structure of the existing StepKind in mind.

[kwxm]

I don't understand generics or (especially) type families very well, but if I add a case for Par1 here the whole thing compiles without error. I can also remove the cases involving TypeError and it still all works OK, presumably because they don't come into play for StepKind. I'm not sure exactly what I'm trying to say, but I guess I'm wondering if something could change that would make this stop working (although I suppose the test should detect that kind of thing).

[effectfully]

OK, I've added

    CountConstructorsEnum (Rec1 _ _) = TypeError ('Text "Cannot be a non-enumeration type")
    CountConstructorsEnum (Par1 _ _) =
        TypeError ('Text "If you really want a parameterized type, handle this clause")

It doesn't really matter, if one of those isn't handled, at worst you'll get a less readable type checking error and that's it, we don't even need the test for that.

[kwxm]

We can also compute this number dynamically by looking at the enumeration of StepKind. Would it be sensible to do that, or is this safer?

[effectfully]

Great idea, I've added that test alongside the other one. Thanks!