Don't use external API

The original implementation was based on code use external to this module.
Because of that, we had an additional constraint of `Ord k`—from `union`.
However, we know the implementation in this module.
So, we can use that knowledge to remove the `Ord k` constraint`.

Author: joneshf

src/Data/Map.purs

@@ -77,8 +77,21 @@ instance foldableMap :: Foldable (Map k) where
   foldr   f z m = foldr   f z (values m)
   foldMap f   m = foldMap f   (values m)
 
-instance traversableMap :: Ord k => Traversable (Map k) where
-  traverse f ms = foldr (\x acc -> union <$> x <*> acc) (pure empty) ((map (uncurry singleton)) <$> (traverse f <$> toList ms))
+instance traversableMap :: Traversable (Map k) where
+  traverse f Leaf = pure Leaf
+  traverse f (Two left k v right) =
+    Two <$> traverse f left
+        <*> pure k
+        <*> f v
+        <*> traverse f right
+  traverse f (Three left k1 v1 mid k2 v2 right) =
+    Three <$> traverse f left
+          <*> pure k1
+          <*> f v1
+          <*> traverse f mid
+          <*> pure k2
+          <*> f v2
+          <*> traverse f right
   sequence = traverse id
 
 -- | Render a `Map` as a `String`