make foldrWithIndex ordered

src/Data/Map.purs

@@ -105,7 +105,7 @@ instance foldableMap :: Foldable (Map k) where
 
 instance foldableWithIndexMap :: FoldableWithIndex k (Map k) where
   foldlWithIndex f z m = foldl (uncurry <<< (flip f)) z $ asList $ toUnfoldable m
-  foldrWithIndex f z m = foldr (uncurry f) z $ asList $ toUnfoldable m
+  foldrWithIndex f z m = foldr (uncurry f) z $ asList $ toAscUnfoldable m
   foldMapWithIndex f m = foldMap (uncurry f) $ asList $ toUnfoldable m
 
 asList :: forall k v. List (Tuple k v) -> List (Tuple k v)

test/Test/Data/Map.purs

@@ -8,8 +8,9 @@ import Control.Monad.Eff.Exception (EXCEPTION)
 import Control.Monad.Eff.Random (RANDOM)
 import Data.Array as A
 import Data.Foldable (foldl, for_, all)
+import Data.FoldableWithIndex (foldrWithIndex)
 import Data.Function (on)
-import Data.List (List(Cons), groupBy, length, nubBy, singleton, sort, sortBy)
+import Data.List (List(..), (:), groupBy, length, nubBy, singleton, sort, sortBy)
 import Data.List.NonEmpty as NEL
 import Data.Map as M
 import Data.Map.Gen (genMap)
@@ -333,3 +334,8 @@ mapTests = do
        <> ", mmin: " <> show mmin
        <> ", mmax: " <> show mmax
        <> ", key: " <> show key
+
+  log "foldrWithIndex maintains order"
+  quickCheck \(TestMap m :: TestMap Int Int) ->
+    let outList = foldrWithIndex (\i a b -> (Tuple i a) : b) Nil m
+    in outList == sort outList