Add test for T18574

testsuite/tests/perf/should_run/T18574.hs

+import Data.Maybe
+
+main :: IO ()
+main = print $ even $ sum $ catMaybes $ map xx ([1..100000000] :: [Int])
+  where
+    xx n | even n    = Just n
+         | otherwise = Nothing

testsuite/tests/perf/should_run/T18574.stdout

+True

testsuite/tests/perf/should_run/all.T

@@ -379,3 +379,9 @@ test('UniqLoop',
       ],
      compile_and_run,
      ['-O -package ghc'])
+
+test('T18574',
+    [collect_stats('bytes allocated', 5), only_ways(['normal'])],
+    compile_and_run,
+    ['-O'])
+