Consistently use lookupResToMaybe (#460)

Author: sjakobi

Data/HashMap/Internal.hs

@@ -1426,9 +1426,7 @@ alterFEager f !k m = (<$> f mv) $ \case
 
   where !h = hash k
         !lookupRes = lookupRecordCollision h k m
-        !mv = case lookupRes of
-           Absent -> Nothing
-           Present v _ -> Just v
+        !mv = lookupResToMaybe lookupRes
 {-# INLINABLE alterFEager #-}
 
 -- | \(O(n \log m)\) Inclusion of maps. A map is included in another map if the keys

Data/HashMap/Internal/Strict.hs

@@ -438,9 +438,7 @@ alterFEager f !k !m = (<$> f mv) $ \fres ->
 
   where !h = hash k
         !lookupRes = HM.lookupRecordCollision h k m
-        !mv = case lookupRes of
-          Absent -> Nothing
-          Present v _ -> Just v
+        !mv = HM.lookupResToMaybe lookupRes
 {-# INLINABLE alterFEager #-}
 
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