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diff --git a/testsuite/tests/typecheck/should_compile/tc222.hs b/testsuite/tests/typecheck/should_compile/tc222.hs
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+{-# LANGUAGE ImplicitParams, Rank2Types #-}
+
+-- Tests impredivative polymorphism with left-to-right
+-- flow information; see the uses of "$"
+
+module TestIP where
+
+import Control.Monad.ST
+import Data.STRef
+
+-- Here's a use of runST with ($)
+foo = runST $ (do { v <- newSTRef 0; readSTRef v })
+
+-- Here's a use of implicit parameters with ($)
+
+type PPDoc = (?env :: Int) => Char -> Char
+
+f :: PPDoc -> PPDoc
+f c = g $ c
+
+-- Fully annotated version of f, as compiled by GHC 6.4.2
+--
+-- f ?env c = $ (C->C) (C->C) 
+--		(\(x:C->C). g ?env (\?env. x))
+--		(c ?env)
+--
+-- The subsumption test needed from the call to $ is this:
+--	?env => (?env => C -> C) -> C -> C   <=  a->b
+--	(?env => C -> C) -> C -> C   <=  a->b
+--	(a) C->C <= b
+--	(b) a <= (?env => C -> C)
+-- And perhaps surprisingly (b) succeeds!
+
+g :: PPDoc -> PPDoc
+g d = d
+
+
+