constraints inside classes

[Mark P Jones]

| Hugs and GHC (but not NHC) erroneously accept the following:
| 
| class Foo a where
|         f :: Eq a => a -> Bool

This behavior of Hugs is intentional, and is documented as a non-bug
on the Hugs web pages:  (right at the end)

  http://cvs.haskell.org/Hugs/pages/bugsandfeatures.htm

I don't know how the "non bug" status was determined, but perhaps
it reflects a view that the real bug is in the language report,
where a demonstrably unnecessary, and potentially limiting restriction
is imposed.

All the best,
Mark