1 files changed, 35 insertions, 0 deletions
diff --git a/compiler/GHC/Data/EnumSet.hs b/compiler/GHC/Data/EnumSet.hs
new file mode 100644
index 0000000000..61d6bf002b
--- /dev/null
+++ b/compiler/GHC/Data/EnumSet.hs
@@ -0,0 +1,35 @@
+-- | A tiny wrapper around 'IntSet.IntSet' for representing sets of 'Enum'
+-- things.
+module GHC.Data.EnumSet
+    ( EnumSet
+    , member
+    , insert
+    , delete
+    , toList
+    , fromList
+    , empty
+    ) where
+
+import GHC.Prelude
+
+import qualified Data.IntSet as IntSet
+
+newtype EnumSet a = EnumSet IntSet.IntSet
+
+member :: Enum a => a -> EnumSet a -> Bool
+member x (EnumSet s) = IntSet.member (fromEnum x) s
+
+insert :: Enum a => a -> EnumSet a -> EnumSet a
+insert x (EnumSet s) = EnumSet $ IntSet.insert (fromEnum x) s
+
+delete :: Enum a => a -> EnumSet a -> EnumSet a
+delete x (EnumSet s) = EnumSet $ IntSet.delete (fromEnum x) s
+
+toList :: Enum a => EnumSet a -> [a]
+toList (EnumSet s) = map toEnum $ IntSet.toList s
+
+fromList :: Enum a => [a] -> EnumSet a
+fromList = EnumSet . IntSet.fromList . map fromEnum
+
+empty :: EnumSet a
+empty = EnumSet IntSet.empty