fun deps and constraints in data decls

[Iavor Diatchki]

 > module Test where

Hello,

Both GHC and Hugs report an error on the example bellow,
which to me seems wrong.  Is this a bug, or am I missing something?

 > class C a b | a -> b
 > newtype C a b => T a = T a
 > t :: C a b => a -> T a
 > t = T

The error reported is that "b" is an undefined type variable.
Since "a" determines "b" using the functional dependency,
I was expecting the example to work.  I expected the type
of the data constructor "T" to be as the one given in the
type signature for "t", as I though that constraints on
data/newtype declarations simply were added to the constructors.
Both of the implementations are happy if I simply comment out the 
constraint,
so they do not consider the type signature for "t" to be malformed in 
any way.

bye
iavor