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diff --git a/testsuite/tests/typecheck/should_run/tcrun036.hs b/testsuite/tests/typecheck/should_run/tcrun036.hs
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+{-# LANGUAGE Rank2Types #-}
+
+-- Another test for the new feature that contexts in a mutually
+-- recursive group do not need to be of the same length
+-- I'm putting it here mainly to document the need
+
+-- GHC used to say:
+-- 
+-- Bug.lhs:23:10:
+--     Inferred type is less polymorphic than expected
+--      Quantified type variable `c' is mentioned in the environment:
+--        printCatalog :: c -> IO () (bound at Bug.lhs:28:0)
+--    In the `viewCatalog' field of a record
+
+-- Bug.lhs:27:0:
+--    Contexts differ in length
+--    When matching the contexts of the signatures for
+--      printer :: Viewer
+--      printCatalog :: forall c. (Catalog c) => View c
+--    The signature contexts in a mutually recursive group should all be identical
+
+module Main where
+
+class Catalog c where
+  traverse :: c -> Viewer -> IO ()
+
+instance Catalog Int where
+  traverse i v = viewShowable v i
+
+type View a = a -> IO ()
+
+data Viewer = Viewer {
+    viewShowable :: forall s. Show s => View s,
+    viewCatalog :: forall c. Catalog c => View c
+  }
+
+printer :: Viewer
+--printer = Viewer {
+--  viewCatalog = \x -> traverse x printer,
+--  viewShowable = putStrLn . show }
+printer = Viewer {
+  viewCatalog = printCatalog,
+  viewShowable = putStrLn . show }
+
+printCatalog :: forall c. Catalog c => View c
+printCatalog x = traverse x printer
+
+data X = X {
+    cat :: Int
+  }
+
+instance Catalog X where
+  traverse x v = do
+    viewCatalog v (cat x)
+
+main = do
+  let x = X { cat = 20 }
+  traverse x printer