From ebbb68be22d861cd38915edd259e7e0b3b894e10 Mon Sep 17 00:00:00 2001
From: Artyom <yom@artyom.me>
Date: Tue, 5 Apr 2016 12:38:19 +0300
Subject: [PATCH] Generalise hoistCofree

---
 src/Control/Comonad/Cofree.hs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/Control/Comonad/Cofree.hs b/src/Control/Comonad/Cofree.hs
index ea33bdd..56d3c47 100644
--- a/src/Control/Comonad/Cofree.hs
+++ b/src/Control/Comonad/Cofree.hs
@@ -1,5 +1,4 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE UndecidableInstances #-}
@@ -125,7 +124,7 @@ unfold f c = case f c of
 unfoldM :: (Traversable f, Monad m) => (b -> m (a, f b)) -> b -> m (Cofree f a)
 unfoldM f = f >=> \ (x, t) -> (x :<) `liftM` Data.Traversable.mapM (unfoldM f) t
 
-hoistCofree :: Functor f => (forall x . f x -> g x) -> Cofree f a -> Cofree g a
+hoistCofree :: Functor f => (f (Cofree g a) -> g (Cofree g a)) -> Cofree f a -> Cofree g a
 hoistCofree f (x :< y) = x :< f (hoistCofree f <$> y)
 
 instance Functor f => ComonadCofree f (Cofree f) where
@@ -302,7 +301,7 @@ cofreeDataType = mkDataType "Control.Comonad.Cofree.Cofree" [cofreeConstr]
 #endif
 
 instance ComonadHoist Cofree where
-  cohoist = hoistCofree
+  cohoist f = hoistCofree f
 
 instance ComonadEnv e w => ComonadEnv e (Cofree w) where
   ask = ask . lower