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diff --git a/testsuite/tests/deSugar/should_run/T3126.hs b/testsuite/tests/deSugar/should_run/T3126.hs
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+++ b/testsuite/tests/deSugar/should_run/T3126.hs
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+{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Main where
+import Data.String
+
+-- {{{ Num literals
+newtype N = N Int deriving (Show,Eq)
+
+instance Num N where
+  fromInteger 0 = error "0"
+  fromInteger 1 = N 0
+  fromInteger _ = N 1
+
+f x = case x of
+        1 -> False
+        0 -> True
+
+g x = case x of
+        1 -> False
+        _ -> case x of
+              0 -> True
+              _ -> error "No match"
+
+testNum = do
+  print $ g (N 0)
+  print $ f (N 0)
+
+-- }}}
+
+-- {{{ IsString literals
+newtype S = S String deriving Eq
+
+instance IsString S where 
+  fromString []    = error "[]"
+  fromString (_:_) = S "."
+
+fs x = case x of
+        "." -> False
+        ""  -> True
+
+gs x = case x of
+        "." -> False
+        _   -> case x of
+                 "" -> True
+                 _  -> error "No match"
+
+testIsString = do
+  print $ gs (S ".")
+  print $ fs (S ".")
+
+-- }}}
+
+main = do { testNum; testIsString }
+