Add performance test for #205

When the timeout limit is raised, the test finishes after ~8s on my
laptop.

Author: sjakobi

prettyprinter/test/Testsuite/Main.hs

@@ -53,6 +53,8 @@ tests = testGroup "Tests"
                    groupingPerformance
         , testCase "fillSep performance"
                    fillSepPerformance
+        , testCase "Issue 205"
+                   issue205
         ]
     , testGroup "Regression tests"
         [ testCase "layoutSmart: softline behaves like a newline (#49)"
@@ -285,6 +287,24 @@ fillSepPerformance = docPerformanceTest (pathological 1000)
     pathological :: Int -> Doc ann
     pathological n = iterate (\x -> fillSep ["a", x <+> "b"] ) "foobar" !! n
 
+issue205 :: Assertion
+issue205 = do
+    let doc = fillSep (replicate 30 (sep ["abc", "xyz" :: Doc ()]))
+        t = renderStrict (layoutSmart defaultLayoutOptions doc)
+    timeout 1000000 (evaluate t) >>= \t' -> case t' of
+      Nothing -> assertFailure "Timeout!"
+      Just _success -> pure ()
+  where
+{-
+docPerformanceTest doc
+  = timeout 10000000 (forceDoc doc) >>= \doc' -> case doc' of
+    Nothing -> assertFailure "Timeout!"
+    Just _success -> pure ()
+  where
+    forceDoc :: Doc ann -> IO ()
+    forceDoc = evaluate . foldr seq () . show
+-}
+
 regressionLayoutSmartSoftline :: Assertion
 regressionLayoutSmartSoftline
   = let doc = "a" <> softline <> "b"