Distinguish between undefined effect data and its relinker (#247)

Moreover, now trying to access undefinedRelinker will properly give you the call
stack of where the relinker was called (i.e. in which call to cloneEnv), not
where it was put into Storage (unfortunately I couldn't make it work for
undefinedEffect).

effectful-core/src/Effectful/Dispatch/Dynamic.hs

@@ -1031,7 +1031,8 @@ localBorrow (LocalEnv les) strategy k = case strategy of
 {-# INLINE localBorrow #-}
 
 copyRefs
-  :: forall es srcEs destEs. KnownSubset es srcEs
+  :: forall es srcEs destEs
+   . (HasCallStack, KnownSubset es srcEs)
   => Env srcEs
   -> Env destEs
   -> IO (Env (es ++ destEs))

effectful-core/src/Effectful/Internal/Env.hs

@@ -5,6 +5,12 @@ module Effectful.Internal.Env
   ( -- * The environment
     Env(..)
   , Storage(..)
+  , AnyEffect
+  , toAnyEffect
+  , fromAnyEffect
+  , AnyRelinker
+  , toAnyRelinker
+  , fromAnyRelinker
 
     -- ** Relinker
   , Relinker(..)
@@ -84,18 +90,36 @@ data Storage = Storage
   { stSize      :: !Int
   , stVersion   :: !Int
   , stVersions  :: !(MutablePrimArray RealWorld Int)
-  , stEffects   :: !(SmallMutableArray RealWorld Any)
-  , stRelinkers :: !(SmallMutableArray RealWorld Any)
+  , stEffects   :: !(SmallMutableArray RealWorld AnyEffect)
+  , stRelinkers :: !(SmallMutableArray RealWorld AnyRelinker)
   }
 
+-- | Effect in 'Storage'.
+newtype AnyEffect = AnyEffect Any
+
+toAnyEffect :: EffectRep (DispatchOf e) e -> AnyEffect
+toAnyEffect = AnyEffect . toAny
+
+fromAnyEffect :: AnyEffect -> EffectRep (DispatchOf e) e
+fromAnyEffect (AnyEffect e) = fromAny e
+
+-- | Relinker in 'Storage'.
+newtype AnyRelinker = AnyRelinker Any
+
+toAnyRelinker :: Relinker (EffectRep (DispatchOf e)) e -> AnyRelinker
+toAnyRelinker = AnyRelinker . toAny
+
+fromAnyRelinker :: AnyRelinker -> Relinker (EffectRep (DispatchOf e)) e
+fromAnyRelinker (AnyRelinker f) = fromAny f
+
 ----------------------------------------
 -- Relinker
 
 -- | A function for relinking 'Env' objects stored in the handlers and/or making
 -- a deep copy of the representation of the effect when cloning the environment.
 newtype Relinker :: (Effect -> Type) -> Effect -> Type where
   Relinker
-    :: ((forall es. Env es -> IO (Env es)) -> rep e -> IO (rep e))
+    :: (HasCallStack => (forall es. Env es -> IO (Env es)) -> rep e -> IO (rep e))
     -> Relinker rep e
 
 -- | A dummy 'Relinker'.
@@ -132,7 +156,7 @@ emptyEnv = Env 0
   <*> (newIORef' =<< emptyStorage)
 
 -- | Clone the environment to use it in a different thread.
-cloneEnv :: Env es -> IO (Env es)
+cloneEnv :: HasCallStack => Env es -> IO (Env es)
 cloneEnv (Env offset refs storage0) = do
   Storage storageSize version vs0 es0 fs0 <- readIORef' storage0
   vsSize <- getSizeofMutablePrimArray  vs0
@@ -150,10 +174,10 @@ cloneEnv (Env offset refs storage0) = do
         0 -> pure ()
         k -> do
           let i = k - 1
-          Relinker f <- fromAny <$> readSmallArray fs i
+          Relinker relinker <- fromAnyRelinker <$> readSmallArray fs i
           readSmallArray es i
-            >>= f (relinkEnv storage) . fromAny
-            >>= writeSmallArray' es i . toAny
+            >>= relinker (relinkEnv storage) . fromAnyEffect
+            >>= writeSmallArray' es i . toAnyEffect
           relinkEffects i
   relinkEffects storageSize
   pure $ Env offset refs storage
@@ -163,7 +187,8 @@ cloneEnv (Env offset refs storage0) = do
 --
 -- @since 2.2.0.0
 restoreEnv
-  :: Env es -- ^ Destination.
+  :: HasCallStack
+  => Env es -- ^ Destination.
   -> Env es -- ^ Source.
   -> IO ()
 restoreEnv dest src = do
@@ -307,7 +332,7 @@ getEnv
   -> IO (EffectRep (DispatchOf e) e)
 getEnv env = do
   (i, es) <- getLocation @e env
-  fromAny <$> readSmallArray es i
+  fromAnyEffect <$> readSmallArray es i
 
 -- | Replace the data type in the environment with a new value (in place).
 putEnv
@@ -317,7 +342,7 @@ putEnv
   -> IO ()
 putEnv env e = do
   (i, es) <- getLocation @e env
-  writeSmallArray' es i (toAny e)
+  writeSmallArray' es i (toAnyEffect e)
 
 -- | Modify the data type in the environment and return a value (in place).
 stateEnv
@@ -327,8 +352,8 @@ stateEnv
   -> IO a
 stateEnv env f = do
   (i, es) <- getLocation @e env
-  (a, e) <- f . fromAny <$> readSmallArray es i
-  writeSmallArray' es i (toAny e)
+  (a, e) <- f . fromAnyEffect <$> readSmallArray es i
+  writeSmallArray' es i (toAnyEffect e)
   pure a
 
 -- | Modify the data type in the environment (in place).
@@ -339,14 +364,14 @@ modifyEnv
   -> IO ()
 modifyEnv env f = do
   (i, es) <- getLocation @e env
-  e <- f . fromAny <$> readSmallArray es i
-  writeSmallArray' es i (toAny e)
+  e <- f . fromAnyEffect <$> readSmallArray es i
+  writeSmallArray' es i (toAnyEffect e)
 
 -- | Determine location of the effect in the environment.
 getLocation
   :: forall e es. (HasCallStack, e :> es)
   => Env es
-  -> IO (Int, SmallMutableArray RealWorld Any)
+  -> IO (Int, SmallMutableArray RealWorld AnyEffect)
 getLocation (Env offset refs storage) = do
   let i       = offset + 2 * reifyIndex @e @es
       ref     = indexPrimArray refs  i
@@ -368,8 +393,8 @@ getLocation (Env offset refs storage) = do
 emptyStorage :: HasCallStack => IO Storage
 emptyStorage = Storage 0 (noVersion + 1)
   <$> newPrimArray 0
-  <*> newSmallArray 0 undefinedData
-  <*> newSmallArray 0 undefinedData
+  <*> newSmallArray 0 undefinedEffect
+  <*> newSmallArray 0 undefinedRelinker
 
 -- | Insert an effect into the storage and return its reference.
 insertEffect
@@ -386,21 +411,21 @@ insertEffect storage e f = do
     GT -> error $ "size (" ++ show size ++ ") > len0 (" ++ show len0 ++ ")"
     LT -> do
       writePrimArray   vs0 size version
-      writeSmallArray' es0 size (toAny e)
-      writeSmallArray' fs0 size (toAny f)
+      writeSmallArray' es0 size (toAnyEffect e)
+      writeSmallArray' fs0 size (toAnyRelinker f)
       writeIORef' storage $ Storage (size + 1) (version + 1) vs0 es0 fs0
       pure (size, version)
     EQ -> do
       let len = doubleCapacity len0
       vs <- newPrimArray len
-      es <- newSmallArray len undefinedData
-      fs <- newSmallArray len undefinedData
+      es <- newSmallArray len undefinedEffect
+      fs <- newSmallArray len undefinedRelinker
       copyMutablePrimArray  vs 0 vs0 0 size
       copySmallMutableArray es 0 es0 0 size
       copySmallMutableArray fs 0 fs0 0 size
       writePrimArray   vs size version
-      writeSmallArray' es size (toAny e)
-      writeSmallArray' fs size (toAny f)
+      writeSmallArray' es size (toAnyEffect e)
+      writeSmallArray' fs size (toAnyRelinker f)
       writeIORef' storage $ Storage (size + 1) (version + 1) vs es fs
       pure (size, version)
 
@@ -412,8 +437,8 @@ deleteEffect storage ref = do
   when (ref /= size - 1) $ do
     error $ "ref (" ++ show ref ++ ") /= size - 1 (" ++ show (size - 1) ++ ")"
   writePrimArray  vs ref noVersion
-  writeSmallArray es ref undefinedData
-  writeSmallArray fs ref undefinedData
+  writeSmallArray es ref undefinedEffect
+  writeSmallArray fs ref undefinedRelinker
   writeIORef' storage $ Storage (size - 1) version vs es fs
 
 -- | Relink the environment to use the new storage.
@@ -427,8 +452,11 @@ doubleCapacity n = max 1 n * 2
 noVersion :: Int
 noVersion = 0
 
-undefinedData :: HasCallStack => a
-undefinedData = error "undefined data"
+undefinedEffect :: HasCallStack => AnyEffect
+undefinedEffect = toAnyEffect $ error "undefined effect"
+
+undefinedRelinker :: AnyRelinker
+undefinedRelinker = toAnyRelinker $ Relinker $ \_ _ -> error "undefined relinker"
 
 -- | A strict version of 'writeSmallArray'.
 writeSmallArray' :: SmallMutableArray RealWorld a -> Int -> a -> IO ()

effectful-core/src/Effectful/Internal/Monad.hs

@@ -279,7 +279,7 @@ type instance DispatchOf NonDet = Dynamic
 
 -- | @since 2.2.0.0
 instance NonDet :> es => Alternative (Eff es) where
-  empty   = withFrozenCallStack (send Empty)
+  empty   = send Empty
   a <|> b = send (a :<|>: b)
 
 -- | @since 2.2.0.0

effectful-core/src/Effectful/NonDet.hs

@@ -111,12 +111,14 @@ noError :: Either (cs, e) a -> Either cs a
 noError = either (Left . fst) Right
 
 cloneLocalEnv
-  :: LocalEnv localEs handlerEs
+  :: HasCallStack
+  => LocalEnv localEs handlerEs
   -> Eff es (LocalEnv localEs handlerEs)
 cloneLocalEnv = coerce . unsafeEff_ . cloneEnv . coerce
 
 restoreLocalEnv
-  :: LocalEnv localEs handlerEs
+  :: HasCallStack
+  => LocalEnv localEs handlerEs
   -> LocalEnv localEs handlerEs
   -> Eff es ()
 restoreLocalEnv dest src = unsafeEff_ $ restoreEnv (coerce dest) (coerce src)