Test Trac #3118

testsuite/tests/ghc-regress/simplCore/should_compile/T3118.hs

+-- Test Trac #3118
+
+-- The test is quite delicate.  It aims to get 'f' to look like
+--   f y = case x of
+--             Red -> (y, y)
+--	       _ -> let v = case x of 
+--	       		       Green -> 2
+--	       		       Blue  -> 3
+--	            in (v, 5)
+--
+-- And now float the inner case to top level
+-- so that it's not so obvious that the Red case
+-- cannot occur.  This crashed GHC 6.10.
+--
+-- It's delicate to make the bug show up
+--  (a) because it relies on not "seeing" that
+--      x = Red until later.
+--  (b) because dropping the Red case must happen
+--      before float-out, which itself happens v early
+
+-- In the original report, the x=Red was concealed by profiling
+
+module T3118 where
+
+data Colour = Red | Green | Blue
+
+
+{-# NOINLINE [0] f #-}
+g x = Red
+
+x = g True
+
+f :: Int -> (Int,Int)
+f y = case x of
+         Red -> (y, y)
+	 xx -> let v = case xx of 
+	     	          Red -> 1
+			  Green -> 2
+			  Blue  -> 3
+	         in (v, 5)

testsuite/tests/ghc-regress/simplCore/should_compile/all.T

@@ -36,4 +36,5 @@ test('spec003', normal, compile, [''])
 test('rule1', normal, compile, [''])
 
 test('strict-float', normal, compile, [''])
+test('T3118', normal, compile, [''])