Use the preprocessor to only import Semigroup when we need to

Author: HuwCampbell

optparse-applicative.cabal

@@ -156,5 +156,5 @@ test-suite tests
                      , optparse-applicative
                      , QuickCheck                      >= 2.8 && < 2.17
 
-  if !impl(ghc >= 8)
+  if impl(ghc < 8)
     build-depends:     semigroups

src/Options/Applicative/Builder/Internal.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 module Options.Applicative.Builder.Internal (
   -- * Internals
   Mod(..),
@@ -27,7 +28,9 @@ module Options.Applicative.Builder.Internal (
 import Control.Applicative
 import Control.Monad (mplus)
 import Data.List.NonEmpty (NonEmpty)
+#if __GLASGOW_HASKELL__ < 804
 import Data.Semigroup hiding (Option)
+#endif
 import Prelude
 
 import Options.Applicative.Common

src/Options/Applicative/Types.hs

@@ -57,7 +57,9 @@ import Control.Monad.Trans.Class (lift)
 import Control.Monad.Trans.Reader (ReaderT, ask)
 import qualified Control.Monad.Fail as Fail
 import Data.List.NonEmpty (NonEmpty)
+#if __GLASGOW_HASKELL__ < 804
 import Data.Semigroup hiding (Option)
+#endif
 import Prelude
 
 import System.Exit (ExitCode(..))