Test Trac #7797

tests/perf/should_run/T7797.hs

@@ -0,0 +1,15 @@
+{-# LANGUAGE ExistentialQuantification #-}
+module Main where
+
+import T7797a 
+
+data Box = forall a. (Size a) => Box a a 
+
+box = Box (go 10000000) (go 10000000) where
+  go :: Int -> [Int]
+  go 0 = []
+  go n = 1 : go (n - 1)
+{-# NOINLINE box #-}
+
+main = print $ case box of
+  Box l r -> size l r

tests/perf/should_run/T7797.stdout

@@ -0,0 +1 @@
+0

tests/perf/should_run/T7797a.hs

@@ -0,0 +1,12 @@
+module T7797a where
+
+class Size t where
+  size :: t -> t -> Int
+  burg :: t -> t
+
+instance (Ord a, Num a) => Size [a] where
+  {-# SPECIALISE instance Size [Int] #-}
+  size (x:xs) (y:ys) | x+y > 4   = size xs ys
+                     | otherwise = size xs ys
+  size _ _ = 0
+  burg = error "urk"

tests/perf/should_run/all.T

@@ -261,3 +261,16 @@ test('T7436',
       ],
      compile_and_run,
      ['-O'])
+
+test('T7797',
+      [stats_num_field('bytes allocated', 
+                      [(wordsize(32), 360940756, 5),
+                    # expected value: 2685858140 (x86/OS X)
+                          # expected: 360940756 (x86/Linux)
+                       (wordsize(64), 480050944, 5)]),
+                          # expected: 480050944 (amd64/Linux)
+      only_ways(['normal'])
+      ],
+     compile_and_run,
+     ['-O'])
+