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{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, UndecidableInstances #-}
{-# OPTIONS_GHC -fwarn-missing-signatures #-}
module Bug where
class C a b | a -> b, b -> a where
f :: a -> b
instance C Int Bool where
f = undefined
instance (C a c, C b d) => C (a -> b) (c -> d) where
f = undefined
foo :: Int -> Int
foo = undefined
bar = f foo
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