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diff --git a/testsuite/tests/printer/Ppr014.hs b/testsuite/tests/printer/Ppr014.hs
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+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
+
+-- from https://ocharles.org.uk/blog/guest-posts/2014-12-19-existential-quantification.html
+
+data HashMap k v = HM  -- ... -- actual implementation
+
+class Hashable v where
+  h :: v -> Int
+
+data HashMapM hm = HashMapM
+  { empty  :: forall k v . hm k v
+  , lookup :: Hashable k => k -> hm k v -> Maybe v
+  , insert :: Hashable k => k -> v -> hm k v -> hm k v
+  , union  :: Hashable k => hm k v -> hm k v -> hm k v
+  }
+
+
+data HashMapE = forall hm . HashMapE (HashMapM hm)
+
+-- public
+mkHashMapE :: Int -> HashMapE
+mkHashMapE = HashMapE . mkHashMapM
+
+-- private
+mkHashMapM :: Int -> HashMapM HashMap
+mkHashMapM salt = HashMapM { {- implementation -} }
+
+instance Hashable String where
+
+type Name = String
+data Gift = G String
+
+giraffe :: Gift
+giraffe = G "giraffe"
+
+addGift :: HashMapM hm -> hm Name Gift -> hm Name Gift
+addGift mod gifts =
+  let
+    HashMapM{..} = mod
+  in
+    insert "Ollie" giraffe gifts
+
+-- -------------------------------
+
+santa'sSecretSalt = undefined
+sendGiftToOllie = undefined
+traverse_ = undefined
+
+sendGifts =
+  case mkHashMapE santa'sSecretSalt of
+    HashMapE (mod@HashMapM{..}) ->
+      let
+        gifts = addGift mod empty
+      in
+        traverse_ sendGiftToOllie $ lookup "Ollie" gifts