Merge pull request #494 from IntersectMBO/wenkokke/rc-fundep

Use functional dependencies rather than type families to enable SPECIALISE

src-control/Control/RefCount.hs

@@ -1,8 +1,9 @@
-{-# LANGUAGE CPP               #-}
-{-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE MagicHash         #-}
-{-# LANGUAGE PatternSynonyms   #-}
-{-# LANGUAGE TypeFamilies      #-}
+{-# LANGUAGE CPP                    #-}
+{-# LANGUAGE DefaultSignatures      #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE MagicHash              #-}
+{-# LANGUAGE PatternSynonyms        #-}
+{-# LANGUAGE TypeFamilies           #-}
 
 module Control.RefCount (
     -- * Using references
@@ -30,15 +31,12 @@ module Control.RefCount (
   , checkForgottenRefs
   ) where
 
-import           Data.Kind (Type)
-import           Data.Primitive.PrimVar
-
 import           Control.DeepSeq
 import           Control.Exception (assert)
 import           Control.Monad (when)
 import           Control.Monad.Class.MonadThrow
 import           Control.Monad.Primitive
-
+import           Data.Primitive.PrimVar
 import           GHC.Stack (CallStack, prettyCallStack)
 
 #ifdef NO_IGNORE_ASSERTS
@@ -195,30 +193,36 @@ instance NFData obj => NFData (Ref obj) where
 -- For objects in this class the guarantee is that (when the 'Ref' rules are
 -- followed) the object's finaliser is called exactly once.
 --
-class RefCounted obj where
-  type FinaliserM obj :: Type -> Type
-  getRefCounter       :: obj -> RefCounter (FinaliserM obj)
+class RefCounted m obj | obj -> m where
+  getRefCounter :: obj -> RefCounter m
 
 #ifdef NO_IGNORE_ASSERTS
 #define HasCallStackIfDebug HasCallStack
 #else
 #define HasCallStackIfDebug ()
 #endif
 
--- GHC says specialising is too complicated! But it's ok, each of these can
--- inline to calling a few other specialised helpers.
-{-# INLINE newRef #-}
-{-# INLINE releaseRef #-}
-{-# INLINE dupRef #-}
-{-# INLINE deRefWeak #-}
-
+{-# SPECIALISE
+    newRef ::
+         RefCounted IO obj
+      => IO ()
+      -> (RefCounter IO -> obj)
+      -> IO (Ref obj)
+  #-}
 -- | Make a new reference.
 --
 -- The given finaliser is run when the last reference is released. The
 -- finaliser is run with async exceptions masked.
 --
+{-# SPECIALISE
+  newRef ::
+      RefCounted IO obj
+    => IO ()
+    -> (RefCounter IO -> obj)
+    -> IO (Ref obj)
+  #-}
 newRef ::
-     (RefCounted obj, FinaliserM obj ~ m, PrimMonad m)
+     (RefCounted m obj, PrimMonad m)
   => HasCallStackIfDebug
   => m ()
   -> (RefCounter m -> obj)
@@ -232,8 +236,14 @@ newRef finaliser mkObject = do
 -- | Release a reference to an object that will no longer be used (via this
 -- reference).
 --
+{-# SPECIALISE
+  releaseRef ::
+       RefCounted IO obj
+    => Ref obj
+    -> IO ()
+  #-}
 releaseRef ::
-     (RefCounted obj, FinaliserM obj ~ m, PrimMonad m, MonadMask m)
+     (RefCounted m obj, PrimMonad m, MonadMask m)
   => HasCallStackIfDebug
   => Ref obj
   -> m ()
@@ -261,6 +271,12 @@ deRef ref@Ref{refobj} =
     `seq` refobj
 #endif
 
+{-# SPECIALISE
+  withRef ::
+       Ref obj
+    -> (obj -> IO a)
+    -> IO a
+  #-}
 {-# INLINE withRef #-}
 -- | Use the object in a 'Ref'. Do not retain the object after the scope of
 -- the body. If you cannot use scoped \"with\" style, use pattern 'DeRef'.
@@ -276,10 +292,16 @@ withRef ref@Ref{refobj} f = do
     assertNoUseAfterRelease ref
     f refobj
 
+{-# SPECIALISE
+  dupRef ::
+       RefCounted IO obj
+    => Ref obj
+    -> IO (Ref obj)
+  #-}
 -- | Duplicate an existing reference, to produce a new reference.
 --
 dupRef ::
-     (RefCounted obj, FinaliserM obj ~ m, PrimMonad m)
+     (RefCounted m obj, PrimMonad m)
   => HasCallStackIfDebug
   => Ref obj
   -> m (Ref obj)
@@ -308,11 +330,17 @@ mkWeakRef Ref {refobj} = WeakRef refobj
 mkWeakRefFromRaw :: obj -> WeakRef obj
 mkWeakRefFromRaw obj = WeakRef obj
 
+{-# SPECIALISE
+  deRefWeak ::
+       RefCounted IO obj
+    => WeakRef obj
+    -> IO (Maybe (Ref obj))
+  #-}
 -- | If the object is still alive, obtain a /new/ normal reference. The normal
 -- rules for 'Ref' apply, including the need to eventually call 'releaseRef'.
 --
 deRefWeak ::
-     (RefCounted obj, FinaliserM obj ~ m, PrimMonad m)
+     (RefCounted m obj, PrimMonad m)
   => HasCallStackIfDebug
   => WeakRef obj
   -> m (Maybe (Ref obj))

src/Database/LSMTree/Internal/BlobFile.hs

@@ -32,8 +32,7 @@ data BlobFile m h = BlobFile {
      }
   deriving stock (Show)
 
-instance RefCounted (BlobFile m h) where
-    type FinaliserM (BlobFile m h) = m
+instance RefCounted m (BlobFile m h) where
     getRefCounter = blobFileRefCounter
 
 instance NFData h => NFData (BlobFile m h) where

src/Database/LSMTree/Internal/MergeSchedule.hs

@@ -325,8 +325,7 @@ data MergingRun m h = MergingRun {
     , mergeRefCounter     :: !(RefCounter m)
     }
 
-instance RefCounted (MergingRun m h) where
-    type FinaliserM (MergingRun m h) = m
+instance RefCounted m (MergingRun m h) where
     getRefCounter = mergeRefCounter
 
 {-# SPECIALISE newMergingRun ::

src/Database/LSMTree/Internal/Run.hs

@@ -101,8 +101,7 @@ instance NFData h => NFData (Run m h) where
       rnf a `seq` rwhnf b `seq` rnf c `seq` rnf d `seq` rnf e `seq`
       rnf f `seq` rnf g `seq` rnf h `seq` rwhnf i `seq` rwhnf j
 
-instance RefCounted (Run m h) where
-    type FinaliserM (Run m h) = m
+instance RefCounted m (Run m h) where
     getRefCounter = runRefCounter
 
 size :: Ref (Run m h) -> NumEntries

src/Database/LSMTree/Internal/WriteBufferBlobs.hs

@@ -112,8 +112,7 @@ data WriteBufferBlobs m h =
 instance NFData h => NFData (WriteBufferBlobs m h) where
   rnf (WriteBufferBlobs a b c) = rnf a `seq` rnf b `seq` rnf c
 
-instance RefCounted (WriteBufferBlobs m h) where
-  type FinaliserM (WriteBufferBlobs m h) = m
+instance RefCounted m (WriteBufferBlobs m h) where
   getRefCounter = writeBufRefCounter
 
 {-# SPECIALISE new :: HasFS IO h -> FS.FsPath -> IO (Ref (WriteBufferBlobs IO h)) #-}

test-control/Test/Control/RefCount.hs

@@ -108,14 +108,12 @@ readRefCount (RefCounter countVar _) = readPrimVar countVar
 #ifdef NO_IGNORE_ASSERTS
 data TestObject = TestObject !(RefCounter IO)
 
-instance RefCounted TestObject where
-    type FinaliserM TestObject = IO
+instance RefCounted IO TestObject where
     getRefCounter (TestObject rc) = rc
 
 data TestObject2 = TestObject2 (Ref TestObject)
 
-instance RefCounted TestObject2 where
-    type FinaliserM TestObject2 = IO
+instance RefCounted IO TestObject2 where
     getRefCounter (TestObject2 (DeRef to1)) = getRefCounter to1
 
 prop_ref_double_free :: Property