Yesod routes must fulfill equality constraint

Yesod/Helpers/Crud.hs

@@ -34,7 +34,6 @@ mkYesodSub "Crud master item"
     [ ("master", [''Yesod])
     , ("item", [''Item])
     , ("Key item", [''SinglePiece])
-    , ("Routes master", [''Eq])
     ] [$parseRoutes|
 /               CrudListR        GET
 /add            CrudAddR         GET POST
@@ -58,24 +57,21 @@ getCrudListR = do
     %a!href=@toMaster.CrudAddR@ Add new item
 |]
 
-getCrudAddR :: (Yesod master, Item item, SinglePiece (Key item),
-                Eq (Routes master))
+getCrudAddR :: (Yesod master, Item item, SinglePiece (Key item))
             => GHandler (Crud master item) master RepHtml
 getCrudAddR = crudHelper
                 "Add new"
                 (Nothing :: Maybe (Key item, item))
                 False
 
-postCrudAddR :: (Yesod master, Item item, SinglePiece (Key item),
-                 Eq (Routes master))
+postCrudAddR :: (Yesod master, Item item, SinglePiece (Key item))
              => GHandler (Crud master item) master RepHtml
 postCrudAddR = crudHelper
                 "Add new"
                 (Nothing :: Maybe (Key item, item))
                 True
 
-getCrudEditR :: (Yesod master, Item item, SinglePiece (Key item),
-                 Eq (Routes master))
+getCrudEditR :: (Yesod master, Item item, SinglePiece (Key item))
              => String -> GHandler (Crud master item) master RepHtml
 getCrudEditR s = do
     itemId <- maybe notFound return $ itemReadId s
@@ -86,8 +82,7 @@ getCrudEditR s = do
         (Just (itemId, item))
         False
 
-postCrudEditR :: (Yesod master, Item item, SinglePiece (Key item),
-                  Eq (Routes master))
+postCrudEditR :: (Yesod master, Item item, SinglePiece (Key item))
               => String -> GHandler (Crud master item) master RepHtml
 postCrudEditR s = do
     itemId <- maybe notFound return $ itemReadId s
@@ -128,7 +123,7 @@ itemReadId :: SinglePiece x => String -> Maybe x
 itemReadId = either (const Nothing) Just . fromSinglePiece
 
 crudHelper
-    :: (Item a, Yesod master, SinglePiece (Key a), Eq (Routes master))
+    :: (Item a, Yesod master, SinglePiece (Key a))
     => String -> Maybe (Key a, a) -> Bool
     -> GHandler (Crud master a) master RepHtml
 crudHelper title me isPost = do

Yesod/Yesod.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 -- | The basic typeclass for a Yesod application.
 module Yesod.Yesod
@@ -39,18 +40,18 @@ import Data.Maybe (isNothing)
 
 -- | This class is automatically instantiated when you use the template haskell
 -- mkYesod function. You should never need to deal with it directly.
-class YesodSite y where
+class Eq (Routes y) => YesodSite y where
     getSite :: Site (Routes y) (Method -> Maybe (Handler y ChooseRep))
 type Method = String
 
 -- | Same as 'YesodSite', but for subsites. Once again, users should not need
 -- to deal with it directly, as the mkYesodSub creates instances appropriately.
-class YesodSubSite s y where
+class Eq (Routes s) => YesodSubSite s y where
     getSubSite :: Site (Routes s) (Method -> Maybe (GHandler s y ChooseRep))
 
 -- | Define settings for a Yesod applications. The only required setting is
 -- 'approot'; other than that, there are intelligent defaults.
-class Yesod a where
+class Eq (Routes a) => Yesod a where
     -- | An absolute URL to the root of the application. Do not include
     -- trailing slash.
     --