recursive group context bug?

[Ashley Yakeley]

I suspect someone's come across this before, so maybe there's an 
explanation for it.

This does not compile:

module Bug where
{
    p :: IO ();
    p = q >>= id;

    q :: (Monad m) => m (IO ());
    q = return p;
}

Bug.hs:3:
    Mismatched contexts
    When matching the contexts of the signatures for
      p :: IO ()
      q :: forall m. (Monad m) => m (IO ())
    The signature contexts in a mutually recursive group should all be 
identical
    When generalising the type(s) for p, q


The code looks correct to me. Why must the signature contexts be 
identical in this case?

-- 
Ashley Yakeley, Seattle WA