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diff --git a/testsuite/tests/gadt/doaitse.hs b/testsuite/tests/gadt/doaitse.hs
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+++ b/testsuite/tests/gadt/doaitse.hs
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+{-# LANGUAGE GADTs, ExistentialQuantification, ScopedTypeVariables,
+             Rank2Types #-}
+
+-- Here's an example from Doaitse Swiestra (Sept 06)
+-- which requires use of scoped type variables
+-- 
+-- It's a cut-down version of a larger program
+--
+-- It's also one which was sensitive to syntactic order
+-- in GHC 6.4; but not in 6.6
+
+module ShouldCompile where
+
+data Exists f = forall a . Exists (f a)
+
+data Ref env a where
+  Zero :: Ref (a,env') a
+  Suc  :: Ref env' a -> Ref (x,env') a
+
+data Find env final = Find (forall a . Ref env a -> Maybe (Ref final a))
+
+data Equal a b where
+  Eq :: Equal a a
+
+sym :: Equal a b -> Equal b a
+sym Eq = Eq
+
+match' :: Ref env' a -> Ref env'' a -> Bool
+match' _ _ = True
+
+match :: Ref env a -> Ref env b -> Maybe (Equal a b)
+match Zero Zero      = Just Eq
+match (Suc x)(Suc y) = match x y
+match _ _            = Nothing
+
+-- Notice the essential type sig for the argument to Exists
+f1 :: forall env.  (Exists (Ref env)) -> Exists (Find  env)
+f1 (Exists (ref1 :: Ref env b))
+  = Exists ( Find (\ ref2 -> case match ref2 ref1 of
+                                Just Eq -> Just Zero
+                                _       -> Nothing
+                  ):: Find env (b,())
+   )
+
+
+-- same as 'f1' except that 'ref1' and 'ref2' are swapped in the  
+-- application of 'match'
+f2 :: forall env.  (Exists (Ref env)) -> Exists (Find  env)
+f2 (Exists (ref1 :: Ref env b))
+   = Exists (Find (\ ref2 -> case match ref1 ref2 of
+                                    Just Eq -> Just Zero
+                                    _       -> Nothing
+                    ) :: Find env (b,())
+     )
+