[Hugs-bugs] type-cheker woes

[Iavor S. Diatchki]

hello,
sorry for the many posts, today seems to have turned
into a bug reporting day.  there seems to be
a probelm with the type checker of the
current cvs version:

 > class {-(Monad m, Monad n) =>-} HasBaseMonad m n | m -> n where
 >  mapBase :: (forall a. n a -> n a) -> m a -> m a
 >
 > instance HasBaseMonad IO IO where
 >  mapBase f x = f x

ERROR "hugs-bug.lhs":10 - Illegal type in class constraint

if i comment-in the commented-out part (the Monad constraints)
i get the following:

ERROR "hugs-bug.lhs":11 - Inferred type is not general enough
*** Expression    : mapBase
*** Expected type : HasBaseMonad IO IO => (forall c. a c -> a c) -> IO b 
-> IO b
*** Inferred type : HasBaseMonad IO IO => (forall b. IO b -> IO b) -> IO 
a -> IO a

if i remove the instance the script loads fine.

-iavor

-- 
==================================================
| Iavor S. Diatchki, Ph.D. student               | 
| Department of Computer Science and Engineering |
| School of OGI at OHSU                          |
| http://www.cse.ogi.edu/~diatchki               |
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