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-- Test purpose:
-- Ensure that missing semigroup warnings are issued
-- correctly if the warning flag is enabled
{-# OPTIONS_GHC -fwarn-semigroup #-}
module SemigroupWarnings where
import Data.Semigroup
-- Bad instance, should complain about missing Semigroup parent
data LacksSemigroup
instance Monoid LacksSemigroup where
mempty = undefined
mappend = undefined
-- Correct instance, should not warn
data HasSemigroup
instance Semigroup HasSemigroup where
(<>) = undefined
instance Monoid HasSemigroup where
mempty = undefined
mappend = undefined
-- Should issue a Prelude clash warning
(<>) = undefined
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