Fix non-canonical-return warnings

Author: andreasabel

src/Distribution/Server/Features/Security/Migration.hs

@@ -206,11 +206,11 @@ data Migrated a = Migrated MigrationStats a | AlreadyMigrated a
   deriving (Functor)
 
 instance Applicative Migrated where
-  pure    = return
+  pure    = AlreadyMigrated
   f <*> x = do f' <- f ; x' <- x ; return $ f' x'
 
 instance Monad Migrated where
-  return = AlreadyMigrated
+  return = pure
   AlreadyMigrated a >>= f = f a
   Migrated stats  a >>= f =
     case f a of

src/Distribution/Server/Framework/BackupRestore.hs

@@ -251,7 +251,7 @@ data Restore a = RestoreDone a
                | RestoreFindBlob BlobId (Bool -> Restore a)
 
 instance Monad Restore where
-  return = RestoreDone
+  return = pure
   RestoreDone x         >>= g = g x
   RestoreFail err       >>= _ = RestoreFail err
   RestoreAddBlob  bs  f >>= g = RestoreAddBlob  bs  $ \bid -> f bid >>= g
@@ -270,7 +270,7 @@ instance Functor Restore where
   fmap = liftM
 
 instance Applicative Restore where
-  pure      = return
+  pure      = RestoreDone
   mf <*> mx = do f <- mf ; x <- mx ; return (f x)
 
 runRestore :: BlobStores -> Restore a -> IO (Either String a)