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{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
module Bug where
type family T t
type family S s
class Show (T c) => C1 c
class Show (T (S d)) => D d
instance (D d, c ~ S d) => C1 c
-- this one fails in GHC 9.2
class Show (T c) => C2 c
instance (D d, c ~ S d, c' ~ c) => C2 c'
-- This one succeeded because it went via lookupInInerts.
-- It should fail, just like the one above.
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