TOSQUASH: compilation fix

Author: jorisdral

src/Database/LSMTree/Internal/MergeSchedule.hs

@@ -18,7 +18,7 @@ module Database.LSMTree.Internal.MergeSchedule (
   , MergingRun (..)
   , NumRuns (..)
   , MergingRunState (..)
-  , NumStepsDone (..)
+  , TotalCredits (..)
     -- * Flushes and scheduled merges
   , updatesWithInterleavedFlushes
   , flushWriteBuffer
@@ -278,9 +278,13 @@ newtype NumRuns = NumRuns { unNumRuns :: Int }
 
 data MergingRunState m h =
     CompletedMerge !(Run m h)
-  | OngoingMerge !(V.Vector (Run m h)) !(PrimVar (PrimState m) Int {- NumStepsDone -}) !(Merge m h)
+  | OngoingMerge
+      !(V.Vector (Run m h))
+      !(PrimVar (PrimState m) Int) -- ^ 'TotalCredits'
+      !(Merge m h)
 
-newtype NumStepsDone = NumStepsDone { unNumStepsDone :: Int }
+-- | The total number of accumulated credits.
+newtype TotalCredits = TotalCredits { unTotalCredits :: Int }
   deriving stock (Show, Eq)
 
 {-# SPECIALISE addReferenceLevels :: TempRegistry IO -> Levels IO h -> IO () #-}
@@ -906,11 +910,11 @@ supplyMergeCredits _ SingleRun{} = pure ()
 supplyMergeCredits (ScaledCredits c) (MergingRun _ _ var) = do
     mergeIsDone <- withMVar var $ \case
       CompletedMerge{} -> pure False
-      (OngoingMerge _rs pvar m) -> do
+      (OngoingMerge _rs totalCreditsVar m) -> do
         -- n >= c
         (n, stepResult) <- Merge.steps m c
-        x <- readPrimVar pvar
-        writePrimVar pvar $! n + x
+        prev <- readPrimVar totalCreditsVar
+        writePrimVar totalCreditsVar $! prev + c
         pure $ stepResult == MergeComplete
     when mergeIsDone $
       modifyMVarMasked_ var $ \case