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diff --git a/testsuite/tests/typecheck/should_compile/tc131.hs b/testsuite/tests/typecheck/should_compile/tc131.hs
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+{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
+
+-- !!! Typechecking of functional dependencies
+-- Showed up (another) bug in the newtype-squashing machinery
+
+
+module ShouldCompile where
+
+class Split2 a b | a -> b, b -> a where
+    combine2 :: (b,b) -> a
+
+class Split4 a b | a -> b, b -> a where
+    combine4 :: (b,b) -> a
+
+newtype Word16 = Word16 Int
+newtype Word32 = Word32 Int
+newtype Word64 = Word64 Int
+
+instance Split2 Word32 Word16 where
+    combine2 = undefined
+
+instance Split2 Word64 Word32 where
+    combine2 a = undefined
+
+instance Split4 Word64 Word16 where
+    combine4 (a, b) = 
+        combine2 ( (combine2 (a, b)), combine2 (a, b))
+
+
+