From d4b206213ef70c4864a3957103beb6f345dcd191 Mon Sep 17 00:00:00 2001
From: William Rusnack <williamrusnack@gmail.com>
Date: Sun, 10 Mar 2024 16:07:24 -0400
Subject: [PATCH] MonadReader instance for CPS RWST

---
 lens.cabal               | 2 +-
 src/Control/Lens/Zoom.hs | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/lens.cabal b/lens.cabal
index 69600aadc..166576545 100644
--- a/lens.cabal
+++ b/lens.cabal
@@ -192,7 +192,7 @@ library
     indexed-traversable           >= 0.1      && < 0.2,
     indexed-traversable-instances >= 0.1      && < 0.2,
     kan-extensions                >= 5        && < 6,
-    mtl                           >= 2.2.1    && < 2.4,
+    mtl                           >= 2.3      && < 2.4,
     parallel                      >= 3.2.1.0  && < 3.3,
     profunctors                   >= 5.5.2    && < 6,
     reflection                    >= 2.1      && < 3,
diff --git a/src/Control/Lens/Zoom.hs b/src/Control/Lens/Zoom.hs
index 5ef78c597..64fc55426 100644
--- a/src/Control/Lens/Zoom.hs
+++ b/src/Control/Lens/Zoom.hs
@@ -46,6 +46,7 @@ import Control.Monad.Trans.Writer.Lazy as Lazy
 import Control.Monad.Trans.Writer.Strict as Strict
 import Control.Monad.Trans.RWS.Lazy as Lazy
 import Control.Monad.Trans.RWS.Strict as Strict
+import Control.Monad.Trans.RWS.CPS as CPS
 import Control.Monad.Trans.Except
 import Control.Monad.Trans.Identity
 import Control.Monad.Trans.Maybe
@@ -102,6 +103,7 @@ type instance Magnified (ReaderT b m) = Effect m
 type instance Magnified ((->)b) = Const
 type instance Magnified (Strict.RWST a w s m) = EffectRWS w s m
 type instance Magnified (Lazy.RWST a w s m) = EffectRWS w s m
+type instance Magnified (CPS.RWST a w s m) = EffectRWS w s m
 type instance Magnified (IdentityT m) = Magnified m
 
 ------------------------------------------------------------------------------
@@ -274,6 +276,10 @@ instance (Monad m, Monoid w) => Magnify (Lazy.RWST b w s m) (Lazy.RWST a w s m)
   magnify l (Lazy.RWST m) = Lazy.RWST $ getEffectRWS #. l (EffectRWS #. m)
   {-# INLINE magnify #-}
 
+instance (Monad m, Monoid w, MonadReader b (CPS.RWST b w s m)) => Magnify (CPS.RWST b w s m) (CPS.RWST a w s m) b a where
+  magnify l m = CPS.rwsT $ getEffectRWS #. l (EffectRWS #. CPS.runRWST m)
+  {-# INLINE magnify #-}
+
 instance Magnify m n b a => Magnify (IdentityT m) (IdentityT n) b a where
   magnify l (IdentityT m) = IdentityT (magnify l m)
   {-# INLINE magnify #-}