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+{-# LANGUAGE TypeFamilies, StandaloneDeriving, FlexibleInstances, GADTs #-}
+module Main where
+
+import Data.Ix
+
+-- Deriving Enum with phantom type parameter
+data T a = R | S | T deriving( Enum, Show )
+
+-- Tests that deriving works for data families
+data family Foo a
+
+data instance Foo Int
+  = A | B | C | D
+  deriving (Eq, Enum)
+
+f :: Foo Int -> Bool
+f A = True
+f B = False
+f _ = True
+
+-- Tests that deriving works for GADTs
+data Bar a where
+   P :: Int -> Bar Int
+   Q :: Bar Int
+
+deriving instance (Eq (Bar Int))
+
+main = do { print [R .. T]
+          ; print (map f [B .. D])
+          ; print [P 3 == P 3, P 4 == Q] }