Confusing error message

[Manuel Chakravarty]

Hi GHC-Developers!

I encountered a confusing error message, which you can
reproduce with 

  type P a = Maybe a

  instance Monad P where
    (>>=)  = error "foo"
    return = error "bar"

I get 

  bug.hs:5: `P' should have 1 argument, but has been given 0 .

with 

  ** ghc 2.05 **

(maybe things changed in the meanwhile.)

The problem in the program is clear, we cannot have an
instance of a type synonym, but that's far from obvious from
the error message.

Cheers,

Manuel