Bugs with fundeps

[Marcin 'Qrczak' Kowalczyk]

The first program let ghc -fglasgow-exts go into infinite loop printing
tcGetTyVar e{-a2145-}.

The second gives an error message about ambiguous type variable. Should
it be an error? It was not an error before.

The third causes panic.

------------------------------------------------------------------------
module Bug1 where

class Foo r a | r -> a where
    foo :: a -> r

instance Foo (Maybe e) e where
    foo = Just

bad:: Num e => Maybe e
bad = foo 0
------------------------------------------------------------------------
module Bug2 where

class Foo r a | r -> a where
    foo :: r -> a

instance Foo [m a] (m a)

bad:: Monad m => m a
bad = foo bar

bar:: Monad m => [m a]
bar = []
------------------------------------------------------------------------
module Bug3 where

class Foo r a | r -> a where
    foo :: r -> a

instance Foo [m a] (m a)

bad:: Monad m => m a
bad = foo bar

bar:: [m a]
bar = []
------------------------------------------------------------------------

-- 
 __("<  Marcin Kowalczyk * qrczak@knm.org.pl http://qrczak.ids.net.pl/
 \__/
  ^^                      SYGNATURA ZASTĘPCZA
QRCZAK