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module WarnMinimal where
class Fine a where
instance Fine Int
-------------------
class Foo a where
foo1 :: a
foo2 :: a
foo1 = foo2
foo2 = foo1
{-# MINIMAL foo1 | foo2 #-}
-- this should generate a warning
instance Foo Int where -- WARNING LINE
-- this should generate no warning
instance Foo Char where
foo1 = 'x'
-- nor should this
instance Foo Bool where
foo2 = True
instance Foo Double where
foo1 = 1
foo2 = 2
-------------------
class Monad' f where
return' :: a -> f a
fmap' :: (a -> b) -> f a -> f b
join' :: f (f a) -> f a
bind' :: f a -> (a -> f b) -> f b
{-# MINIMAL return', (fmap',join' | bind') #-}
fmap' f x = bind' x (return' . f)
join' x = bind' x id
bind' x f = join' (fmap' f x)
instance Monad' [] where
return' = return
fmap' = map
join' = concat
-- no warning
instance Monad' Maybe where
return' = Just
bind' = (>>=)
-- no warning
instance Monad' IO where
return' = return
bind' = (>>=)
fmap' = fmap
join' = (>>= id)
-- no warning
instance Monad' ((->) e) where -- WARNING LINE
return' = const
fmap' = (.)
-- warning!
newtype Id a = Id a
instance Monad' Id where -- WARNING LINE
fmap' f (Id x) = Id (f x)
join' (Id x) = x
-- warning!
newtype Id2 a = Id2 a
instance Monad' Id2 where -- WARNING LINE
fmap' f (Id2 x) = Id2 (f x)
join' (Id2 x) = x
bind' (Id2 x) f = f x
-- warning!
newtype Id3 a = Id3 a
instance Monad' Id3 where -- WARNING LINE
---------
-- incorrect minimal spec
class Cheater a where -- WARNING LINE
cheater :: a
{-# MINIMAL #-} -- warning!
class Cheater2 a where
_cheater2 :: a
{-# MINIMAL #-} -- no warning
class Cheater3 a where -- WARNING LINE
cheater3, cheater3b :: a
{-# MINIMAL cheater3 #-} -- warning!
---------
-- new style warning for classes without explicit spec
instance Num Bool where -- WARNING LINE
class NoExplicit a where
needed :: a
_optional :: a
instance NoExplicit Int where -- WARNING LINE
---------
data Blarg = Blarg
class Eq' a where
(===) :: a -> a -> Bool
(/==) :: a -> a -> Bool
x === y = not (x /== y)
x /== y = not (x === y)
{-# MINIMAL (===) | (/==) #-}
instance Eq' Blarg where -- WARNING LINE
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