Merge pull request #284 from haskell-nix/srk/enumBounds

fix min/maxBound serializer checks

hnix-store-core/src/System/Nix/Build.hs

@@ -24,7 +24,7 @@ data BuildMode
   = BuildMode_Normal -- ^ Perform normal build
   | BuildMode_Repair -- ^ Try to repair corrupted or missing paths by re-building or re-downloading them
   | BuildMode_Check -- ^ Check if the build is reproducible (rebuild and compare to previous build)
-  deriving (Eq, Generic, Ord, Enum, Show)
+  deriving (Bounded, Eq, Generic, Ord, Enum, Show)
 
 -- | Build result status
 data BuildStatus =
@@ -43,7 +43,7 @@ data BuildStatus =
   | BuildStatus_NotDeterministic
   | BuildStatus_ResolvesToAlreadyValid
   | BuildStatus_NoSubstituters
-  deriving (Eq, Generic, Ord, Enum, Show)
+  deriving (Bounded, Eq, Generic, Ord, Enum, Show)
 
 -- | Result of the build
 data BuildResult = BuildResult

hnix-store-remote/src/Data/Serializer/Example.hs

@@ -302,14 +302,24 @@ putBool True  = putInt (1 :: Int8)
 putBool False = putInt (0 :: Int8)
 
 -- | Utility toEnum version checking bounds using Bounded class
-toEnumCheckBounds :: Enum a => Int -> Either String a
+toEnumCheckBounds
+  :: forall a
+   . ( Bounded a
+     , Enum a
+     )
+  => Int
+  -> Either String a
 toEnumCheckBounds = \case
-  x | x < minBound -> Left $ "enum out of min bound " ++ show x
-  x | x > maxBound -> Left $ "enum out of max bound " ++ show x
+  x | x < fromEnum (minBound @a) -> Left $ "enum out of min bound " ++ show x
+  x | x > fromEnum (maxBound @a) -> Left $ "enum out of max bound " ++ show x
   x | otherwise -> Right $ toEnum x
 
 -- | Deserialize @Enum@ to integer
-getEnum :: Enum a => Get a
+getEnum
+  :: ( Bounded a
+     , Enum a
+     )
+  => Get a
 getEnum =
   toEnumCheckBounds <$> getInt
   >>= either fail pure

hnix-store-remote/src/System/Nix/Store/Remote/Serializer.hs

@@ -345,17 +345,23 @@ byteString = Serializer
 
 -- | Utility toEnum version checking bounds using Bounded class
 toEnumCheckBoundsM
-  :: ( Enum a
+  :: forall a m
+   . ( Bounded a
+     , Enum a
      , MonadError SError m
      )
   => Int
   -> m a
 toEnumCheckBoundsM = \case
-  x | x < minBound -> throwError $ SError_EnumOutOfMinBound x
-  x | x > maxBound -> throwError $ SError_EnumOutOfMaxBound x
+  x | x < fromEnum (minBound @a) -> throwError $ SError_EnumOutOfMinBound x
+  x | x > fromEnum (maxBound @a) -> throwError $ SError_EnumOutOfMaxBound x
   x | otherwise -> pure $ toEnum x
 
-enum :: Enum a => NixSerializer r SError a
+enum
+  :: ( Bounded a
+     , Enum a
+     )
+  => NixSerializer r SError a
 enum = Serializer
   { getS = getS int >>= toEnumCheckBoundsM
   , putS = putS int . fromEnum

hnix-store-remote/tests/EnumSpec.hs

@@ -24,7 +24,8 @@ spec :: Spec
 spec = do
   let
     itE
-      :: ( Enum a
+      :: ( Bounded a
+         , Enum a
          , Show a
          )
       => String