testsuite/tests/typecheck/should_compile/tc256.hs


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{-# LANGUAGE TypeFamilies, ConstraintKinds, UndecidableInstances #-}
module Ctx where

import GHC.Prim( Constraint )

type family Indirect :: * -> Constraint
type instance Indirect = Show

class Indirect a => Cls a where

foo :: Cls a => a -> String
foo = show