Hi,
I'm playing around with the type system trying to encode various stuff in
it. I've gotten an error though which it would be useful to understand.
Say I have a type class:
class Foo a
and then I want a datatype like this:
data Bar a = Foo a => C1 | C2 ... | C3
This works fine syntactically but ghc says that I must have at least one
existential type variable in the constraint. Hugs doesn't require that but
has other problems....
Is there a good reason for not allowing the above?
Cheers,
/Josef
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