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diff --git a/testsuite/tests/cpranal/sigs/T19398.hs b/testsuite/tests/cpranal/sigs/T19398.hs
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+++ b/testsuite/tests/cpranal/sigs/T19398.hs
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+{-# LANGUAGE BangPatterns #-}
+
+module T19398 where
+
+data T a = MkT !a !a
+
+f :: T a -> T a
+f (MkT a b) = MkT b a
+{-# NOINLINE f #-}
+
+-- | Should *not* have the CPR property, even though the scrutinee is a
+-- variable with the CPR property. It shows how Test (A) of
+-- Historical Note [Optimistic field binder CPR] is unsound.
+a :: Int -> Int
+a n
+  | n == 0    = n
+  | even n    = case q of MkT x y -> if x == y then x else y
+  | otherwise = case q of MkT x y -> if x == y then y else x
+  where
+    q = f $ f $ f $ f $ f $ f $ f $ MkT n n
+
+-- | Should not have the CPR property, because 'x' will not be unboxed.
+-- It shows how Test (C) of Historical Note [Optimistic field binder CPR] is
+-- unsound.
+c :: (Int, Int) -> Int
+c (x,_) = x
+
+-- | An interesting artifact is that the following function has the Nested CPR
+-- property, and we could in theory exploit that:
+g :: (Int, Int) -> (Int, Int)
+g p@(!x, !y) | x == y = error "blah"
+g p                   = p