1 files changed, 30 insertions, 0 deletions
diff --git a/testsuite/tests/deSugar/should_compile/ds055.hs b/testsuite/tests/deSugar/should_compile/ds055.hs
new file mode 100644
index 0000000000..280fe968d2
--- /dev/null
+++ b/testsuite/tests/deSugar/should_compile/ds055.hs
@@ -0,0 +1,30 @@
+{-# LANGUAGE ExistentialQuantification, DeriveDataTypeable #-}
+
+-- This module requires quite trick desugaring,
+-- because of the context in the existentials
+-- It broke a pre 6.4 GHC
+
+module Foo where
+
+   import Data.Data
+   import Data.HashTable
+
+   data Item = forall a. (Data a) => Leaf Bool a
+             | forall a. (Data a) => Branch Bool a Int Int
+	     deriving (Typeable)
+
+
+   instance Data Item where
+       gfoldl k z (Leaf b v) = z (Leaf b) `k` v
+       gfoldl k z (Branch b v a1 a2) = z (\x -> Branch b x a1 a2) `k` v
+       gunfold _ _ _ = error "urk"
+       toConstr (Leaf _ _) = leafConstr
+       toConstr (Branch _ _ _ _) = branchConstr
+       dataTypeOf _ = itemDataType
+
+   itemDataType = mkDataType "Subliminal.Item" [leafConstr, branchConstr]
+   leafConstr = mkConstr itemDataType "Leaf" [] Prefix
+   branchConstr = mkConstr itemDataType "Branch" [] Prefix
+
+
+