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{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
-- !!! Typechecking of functional dependencies
-- Showed up (another) bug in the newtype-squashing machinery
module ShouldCompile where
class Split2 a b | a -> b, b -> a where
combine2 :: (b,b) -> a
class Split4 a b | a -> b, b -> a where
combine4 :: (b,b) -> a
newtype Word16 = Word16 Int
newtype Word32 = Word32 Int
newtype Word64 = Word64 Int
instance Split2 Word32 Word16 where
combine2 = undefined
instance Split2 Word64 Word32 where
combine2 a = undefined
instance Split4 Word64 Word16 where
combine4 (a, b) =
combine2 ( (combine2 (a, b)), combine2 (a, b))
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