Update IntMap.updateMin and friends (#1065)

Return an empty map for an input empty map instead of calling error.
This matches the behavior of Data.Map.

containers-tests/tests/intmap-properties.hs

@@ -1079,6 +1079,9 @@ test_updateMin = do
     updateMin (\ a -> Just ("X" ++ a)) (fromList [(5,"a"), (-3,"b")]) @?= fromList [(-3, "Xb"), (5, "a")]
     updateMin (\ _ -> Nothing)         (fromList [(5,"a"), (-3,"b")]) @?= singleton 5 "a"
 
+    updateMin (\ a -> Just ("X" ++ a)) (empty :: SMap) @?= empty
+    updateMin (\ _ -> Nothing)         (empty :: SMap) @?= empty
+
 test_updateMax :: Assertion
 test_updateMax = do
     updateMax (\ a -> Just ("X" ++ a)) (fromList [(5,"a"), (3,"b")]) @?= fromList [(3, "b"), (5, "Xa")]
@@ -1087,6 +1090,9 @@ test_updateMax = do
     updateMax (\ a -> Just ("X" ++ a)) (fromList [(5,"a"), (-3,"b")]) @?= fromList [(-3, "b"), (5, "Xa")]
     updateMax (\ _ -> Nothing)         (fromList [(5,"a"), (-3,"b")]) @?= singleton (-3) "b"
 
+    updateMax (\ a -> Just ("X" ++ a)) (empty :: SMap) @?= empty
+    updateMax (\ _ -> Nothing)         (empty :: SMap) @?= empty
+
 test_updateMinWithKey :: Assertion
 test_updateMinWithKey = do
     updateMinWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (fromList [(5,"a"), (3,"b")]) @?= fromList [(3,"3:b"), (5,"a")]
@@ -1095,6 +1101,9 @@ test_updateMinWithKey = do
     updateMinWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (fromList [(5,"a"), (-3,"b")]) @?= fromList [(-3,"-3:b"), (5,"a")]
     updateMinWithKey (\ _ _ -> Nothing)                     (fromList [(5,"a"), (-3,"b")]) @?= singleton 5 "a"
 
+    updateMinWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (empty :: SMap) @?= empty
+    updateMinWithKey (\ _ _ -> Nothing)                     (empty :: SMap) @?= empty
+
 test_updateMaxWithKey :: Assertion
 test_updateMaxWithKey = do
     updateMaxWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (fromList [(5,"a"), (3,"b")]) @?= fromList [(3,"b"), (5,"5:a")]
@@ -1103,6 +1112,9 @@ test_updateMaxWithKey = do
     updateMaxWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (fromList [(5,"a"), (-3,"b")]) @?= fromList [(-3,"b"), (5,"5:a")]
     updateMaxWithKey (\ _ _ -> Nothing)                     (fromList [(5,"a"), (-3,"b")]) @?= singleton (-3) "b"
 
+    updateMaxWithKey (\ k a -> Just ((show k) ++ ":" ++ a)) (empty :: SMap) @?= empty
+    updateMaxWithKey (\ _ _ -> Nothing)                     (empty :: SMap) @?= empty
+
 test_minView :: Assertion
 test_minView = do
     minView (fromList [(5,"a"), (3,"b")]) @?= Just ("b", singleton 5 "a")

containers/src/Data/IntMap/Internal.hs

@@ -2186,7 +2186,7 @@ updateMinWithKey f t =
     go f' (Tip k y) = case f' k y of
                         Just y' -> Tip k y'
                         Nothing -> Nil
-    go _ Nil = error "updateMinWithKey Nil"
+    go _ Nil =  Nil
 
 -- | \(O(\min(n,W))\). Update the value at the maximal key.
 --
@@ -2202,7 +2202,7 @@ updateMaxWithKey f t =
     go f' (Tip k y) = case f' k y of
                         Just y' -> Tip k y'
                         Nothing -> Nil
-    go _ Nil = error "updateMaxWithKey Nil"
+    go _ Nil = Nil
 
 
 data View a = View {-# UNPACK #-} !Key a !(IntMap a)

containers/src/Data/IntMap/Strict/Internal.hs

@@ -771,7 +771,7 @@ updateMinWithKey f t =
     go f' (Tip k y) = case f' k y of
                         Just !y' -> Tip k y'
                         Nothing -> Nil
-    go _ Nil = error "updateMinWithKey Nil"
+    go _ Nil = Nil
 
 -- | \(O(\log n)\). Update the value at the maximal key.
 --
@@ -787,7 +787,7 @@ updateMaxWithKey f t =
     go f' (Tip k y) = case f' k y of
                         Just !y' -> Tip k y'
                         Nothing -> Nil
-    go _ Nil = error "updateMaxWithKey Nil"
+    go _ Nil = Nil
 
 -- | \(O(\log n)\). Update the value at the maximal key.
 --