Import Multiplicity from GHC.Types

This fixes compatibility with GHC 9.2, which did not yet export
Multiplicity from GHC.Exts.

Author: tomsmeding

src/Control/Functor/Linear/Internal/Reader.hs

@@ -35,7 +35,7 @@ import qualified Data.Functor.Linear.Internal.Functor as Data
 import Data.Kind (FUN)
 import Data.Unrestricted.Linear.Internal.Consumable
 import Data.Unrestricted.Linear.Internal.Dupable
-import GHC.Exts (Multiplicity (..))
+import GHC.Types (Multiplicity (..))
 import Prelude.Linear.Internal (runIdentity', ($), (.))
 
 -- # Linear ReaderT