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{-# LANGUAGE QuantifiedConstraints #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
module T17267a where
-- Now rejected
class C a b where
op :: a -> b
uc :: a -> b
uc = oops where
oops :: (C a b => C a b) => a -> b
oops x = op x
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