The orphan instance for MonadState s m => MonadReader s m really can't be used, so replace it with a mere function that runs an operation on a ReaderT into the monad State, allowing to borrow operations on MonadReader in a MonadState context

src/PDF/Box.hs

@@ -12,12 +12,13 @@ module PDF.Box (
     , at
     , atAll
     , edit
+    , runRO
   ) where
 
 import Control.Monad.Except (ExceptT(..), runExceptT)
 import Control.Monad.Fail (MonadFail(..))
 import Control.Monad.State (MonadState(..))
---import Control.Monad.Reader (MonadReader(..))
+import Control.Monad.Reader (ReaderT, runReaderT)
 import Data.Id (Id, IdMap)
 import qualified Data.Id as Id (insert, lookup)
 import Data.Map (Map)
@@ -26,16 +27,8 @@ import Data.OrderedMap (OrderedMap)
 import qualified Data.OrderedMap as OrderedMap (lookup, set)
 import Prelude hiding (fail)
 
-{-
-instance (Monad m, MonadState s m) => MonadReader s m where
-  ask = get
-  local f m = do
-    backup <- get
-    put $ f backup
-    result <- m
-    put backup
-    return result
--}
+runRO :: MonadState s m => ReaderT s m a -> m a
+runRO ro = get >>= runReaderT ro
 
 newtype Index = Index Int
 newtype Maybe_ x = Maybe_ x