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diff --git a/src/Hakyll/Core/CompiledItem.hs b/src/Hakyll/Core/CompiledItem.hs
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+++ b/src/Hakyll/Core/CompiledItem.hs
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+-- | A module containing a box datatype representing a compiled item. This
+-- item can be of any type, given that a few restrictions hold:
+--
+-- * we need a 'Typeable' instance to perform type-safe casts;
+--
+-- * we need a 'Binary' instance so we can serialize these items to the cache;
+--
+-- * we need a 'Writable' instance so the results can be saved.
+--
+{-# LANGUAGE ExistentialQuantification #-}
+module Hakyll.Core.CompiledItem
+    ( CompiledItem (..)
+    , compiledItem
+    , unCompiledItem
+    ) where
+
+import Data.Binary (Binary)
+import Data.Typeable (Typeable, cast)
+import Data.Maybe (fromMaybe)
+
+import Hakyll.Core.Writable
+
+-- | Box type for a compiled item
+--
+data CompiledItem =  forall a.  (Binary a, Typeable a, Writable a)
+                  => CompiledItem a
+
+instance Writable CompiledItem where
+    write p (CompiledItem x) = write p x
+
+-- | Box a value into a 'CompiledItem'
+--
+compiledItem :: (Binary a, Typeable a, Writable a)
+             => a
+             -> CompiledItem
+compiledItem = CompiledItem
+
+-- | Unbox a value from a 'CompiledItem'
+--
+unCompiledItem :: (Binary a, Typeable a, Writable a)
+               => CompiledItem
+               -> a
+unCompiledItem (CompiledItem x) = fromMaybe error' $ cast x
+  where
+    error' = error "Hakyll.Core.CompiledItem.unCompiledItem: Unsupported type"