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{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, FlexibleContexts,
UndecidableInstances, TypeSynonymInstances #-}
-- This test made GHC 6.3 build a superclass loop, in
-- the instance ClassA a String declaration
module Main where
class (Sat (a -> b -> String), ClassB b) => ClassA a b
class ClassB a where
fun :: a -> String
class Sat x where
sat :: x
instance ClassA a b => Sat (a -> b -> String) where
sat = const fun
instance ClassA a String
-- Badness was that the ClassB superclass dict was loopy
--
-- Needs Sat (a -> String -> String), ClassB String
-- --> ClassA a String, ClassB String
-- and adding ClassA gives superclass ClassB.
instance ClassB String where
fun = id
main = print ((sat :: Int -> String -> String) 3 "hello")
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