Use when

Yesod/Auth.hs

@@ -31,6 +31,7 @@ import Language.Haskell.TH.Syntax hiding (lift)
 import qualified Network.Wai as W
 import Text.Hamlet (hamlet)
 import qualified Data.Map as Map
+import Control.Monad                 (when)  
 import Control.Monad.Trans.Class     (lift)
 import Data.Aeson
 import Data.Text (Text)
@@ -110,24 +111,17 @@ setCreds doRedirects creds = do
     maid <- getAuthId creds
     case maid of
         Nothing ->
-            if doRedirects
-                then do
+          when doRedirects $ do
             case authRoute y of
-                        Nothing -> do
-                            rh <- defaultLayout
-                                [QQ(hamlet)| <h1>Invalid login |]
+              Nothing -> do rh <- defaultLayout [QQ(hamlet)| <h1>Invalid login |]
                             sendResponse rh
-                        Just ar -> do
-                            setMessageI Msg.InvalidLogin
+              Just ar -> do setMessageI Msg.InvalidLogin
                             redirect RedirectTemporary ar
-                else return ()
         Just aid -> do
             setSession credsKey $ toSinglePiece aid
-            if doRedirects
-                then do
+            when doRedirects $ do
               setMessageI Msg.NowLoggedIn
               redirectUltDest RedirectTemporary $ loginDest y
-                else return ()
 
 getCheckR :: YesodAuth m => GHandler Auth m RepHtmlJson
 getCheckR = do