[Haskell-cafe] Scope of type variables in associated types

[Andres Loeh]

> class OneStep a
>     data OS a :: *
> instance OneStep (Cons v t)
>     data OS (Cons v t) = t
> 
> class TwoStep a
>     data TS a :: *
> instance (OneStep a, OneStep b) => TwoStep a

instance (OneStep a, OneStep (OS a)) => TwoStep a
?

Cheers,
  Andres