Empty classes of type variables which take an argument.

[George Russell]

The attached file is accepted by GHC 4.08 and Hugs 98.  However if you remove the
declaration of "foo" (and for Hugs, the now unnecessary "where" in the declaration of
class A), both compilers complain.  It appears that in the absence of any information,
GHC and Hugs assume that the subject of a class declaration takes no type parameters.
So how can I declare a trivial class for something which does take a type parameter?
(Yes, I do have a reason for doing this . . .)

NoWhere.hs