testsuite/tests/typecheck/should_fail/T5236.hs


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{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleContexts  #-}

module Main where 

data A
data B

class Id a b | a -> b, b -> a

instance Id A A
instance Id B B

loop :: Id A B => Bool
loop = True

f :: Bool 
f = loop


main :: IO () 
main = return ()