2 files changed, 6 insertions, 3 deletions
diff --git a/compiler/utils/UniqDFM.hs b/compiler/utils/UniqDFM.hs
index 9f81e4dca6..17f2747f83 100644
--- a/compiler/utils/UniqDFM.hs
+++ b/compiler/utils/UniqDFM.hs
@@ -294,7 +294,7 @@ intersectUDFM (UDFM x i) (UDFM y _j) = UDFM (M.intersection x y) i
   -- M.intersection is left biased, that means the result will only have
   -- a subset of elements from the left set, so `i` is a good upper bound.
 
-udfmIntersectUFM :: UniqDFM elt -> UniqFM elt -> UniqDFM elt
+udfmIntersectUFM :: UniqDFM elt1 -> UniqFM elt2 -> UniqDFM elt1
 udfmIntersectUFM (UDFM x i) y = UDFM (M.intersection x (ufmToIntMap y)) i
   -- M.intersection is left biased, that means the result will only have
   -- a subset of elements from the left set, so `i` is a good upper bound.
diff --git a/compiler/utils/UniqDSet.hs b/compiler/utils/UniqDSet.hs
index 4e8c7ed97f..eef545eedd 100644
--- a/compiler/utils/UniqDSet.hs
+++ b/compiler/utils/UniqDSet.hs
@@ -20,7 +20,7 @@ module UniqDSet (
         addOneToUniqDSet, addListToUniqDSet,
         unionUniqDSets, unionManyUniqDSets,
         minusUniqDSet, uniqDSetMinusUniqSet,
-        intersectUniqDSets,
+        intersectUniqDSets, uniqDSetIntersectUniqSet,
         intersectsUniqDSets,
         foldUniqDSet,
         elementOfUniqDSet,
@@ -69,12 +69,15 @@ unionManyUniqDSets sets = foldr1 unionUniqDSets sets
 minusUniqDSet :: UniqDSet a -> UniqDSet a -> UniqDSet a
 minusUniqDSet = minusUDFM
 
-uniqDSetMinusUniqSet :: UniqDSet a -> UniqSet a -> UniqDSet a
+uniqDSetMinusUniqSet :: UniqDSet a -> UniqSet b -> UniqDSet a
 uniqDSetMinusUniqSet xs ys = udfmMinusUFM xs (getUniqSet ys)
 
 intersectUniqDSets :: UniqDSet a -> UniqDSet a -> UniqDSet a
 intersectUniqDSets = intersectUDFM
 
+uniqDSetIntersectUniqSet :: UniqDSet a -> UniqSet b -> UniqDSet a
+uniqDSetIntersectUniqSet xs ys = xs `udfmIntersectUFM` getUniqSet ys
+
 intersectsUniqDSets :: UniqDSet a -> UniqDSet a -> Bool
 intersectsUniqDSets = intersectsUDFM