Deal with the Semigroup/Monoid proposal

base-4.11 made Semigroup a superclass of Monoid. Provide Semigroup
implementations for Monoids.

1 files changed, 7 insertions, 4 deletions

diff --git a/Types/Difference.hs b/Types/Difference.hs
index 4abc75c44..8516a3df7 100644
--- a/Types/Difference.hs
+++ b/Types/Difference.hs
@@ -1,6 +1,7 @@
 {- git-annex repository differences
  -
  - Copyright 2015 Joey Hess <id@joeyh.name>
+ - Copyright 2022 Benjamin Barenblat <bbarenblat@gmail.com>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -67,14 +68,16 @@ instance Eq Differences where
 		, oneLevelBranchHash
 		]
 
-instance Monoid Differences where
-	mempty = Differences False False False
-	mappend a@(Differences {}) b@(Differences {}) = a
+instance Semigroup Differences where
+	a@(Differences {}) <> b@(Differences {}) = a
 		{ objectHashLower = objectHashLower a || objectHashLower b
 		, oneLevelObjectHash = oneLevelObjectHash a || oneLevelObjectHash b
 		, oneLevelBranchHash = oneLevelBranchHash a || oneLevelBranchHash b
 		}
-	mappend _ _ = UnknownDifferences
+	_ <> _ = UnknownDifferences
+
+instance Monoid Differences where
+	mempty = Differences False False False
 
 readDifferences :: String -> Differences
 readDifferences = maybe UnknownDifferences mkDifferences . readish