Add an Eq instance for UniqSet

I left that out by mistake, and it apparently breaks at least one
existing plugin.

Reviewers: christiaanb, austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3518

1 files changed, 17 insertions, 0 deletions

diff --git a/compiler/utils/UniqFM.hs b/compiler/utils/UniqFM.hs
index 8214f1704b..71a092b28e 100644
--- a/compiler/utils/UniqFM.hs
+++ b/compiler/utils/UniqFM.hs
@@ -55,6 +55,7 @@ module UniqFM (
         intersectUFM,
         intersectUFM_C,
         disjointUFM,
+        equalKeysUFM,
         nonDetFoldUFM, foldUFM, nonDetFoldUFM_Directly,
         anyUFM, allUFM, seqEltsUFM,
         mapUFM, mapUFM_Directly,
@@ -76,6 +77,11 @@ import Outputable
 import Data.List (foldl')
 
 import qualified Data.IntMap as M
+#if MIN_VERSION_containers(0,5,9)
+import qualified Data.IntMap.Merge.Lazy as M
+import Control.Applicative (Const (..))
+import qualified Data.Monoid as Mon
+#endif
 import qualified Data.IntSet as S
 import Data.Typeable
 import Data.Data
@@ -339,6 +345,17 @@ nonDetUFMToList (UFM m) = map (\(k, v) -> (getUnique k, v)) $ M.toList m
 ufmToIntMap :: UniqFM elt -> M.IntMap elt
 ufmToIntMap (UFM m) = m
 
+-- Determines whether two 'UniqFm's contain the same keys.
+equalKeysUFM :: UniqFM a -> UniqFM b -> Bool
+#if MIN_VERSION_containers(0,5,9)
+equalKeysUFM (UFM m1) (UFM m2) = Mon.getAll $ getConst $
+      M.mergeA (M.traverseMissing (\_ _ -> Const (Mon.All False)))
+               (M.traverseMissing (\_ _ -> Const (Mon.All False)))
+               (M.zipWithAMatched (\_ _ _ -> Const (Mon.All True))) m1 m2
+#else
+equalKeysUFM (UFM m1) (UFM m2) = M.keys m1 == M.keys m2
+#endif
+
 -- Instances
 
 #if __GLASGOW_HASKELL__ > 710