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{-# OPTIONS -fno-warn-redundant-constraints #-}
module ShouldSucceed where
data Z a b
= C1 (T a)
| C2 (Z [a] [b])
deriving (Show, Read)
data T a
= E1
instance Eq a => Show (T a) where
showsPrec = error "show"
instance Eq a => Read (T a) where
readsPrec = error "read"
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