Make T8761 deterministic, I hope

Summary:
T8761 seems to get different interleaving in its output on
Phabricator, so this switches it to use stderr consistently.

Test Plan: worksforme

Reviewers: goldfire, austin, bgamari, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2363

2 files changed, 13 insertions, 14 deletions

diff --git a/testsuite/tests/th/T8761.hs b/testsuite/tests/th/T8761.hs
index c0c96b96b5..b8177ff3ee 100644
--- a/testsuite/tests/th/T8761.hs
+++ b/testsuite/tests/th/T8761.hs
@@ -34,7 +34,7 @@ do
 
   pats <- sequence [prefixPat, infixPat, recordPat]
   -- pretty print the pattern synonyms:
-  mapM_ (runIO . putStrLn . pprint) pats
+  mapM_ (runIO . hPutStrLn stderr . pprint) pats
   -- splice in the pattern synonyms
   return pats
 
@@ -108,10 +108,10 @@ getY1' = y1 ((1, 2), [3]) -- should yield 3
 do
   infos <- mapM reify [ 'P, 'Pe, 'Pu, 'Pue, 'Pur, 'Purp
                       , 'Pure, 'Purep, 'Pep, 'Pup, 'Puep ]
-  mapM_ (runIO . putStrLn . pprint) infos
-  runIO $ hFlush stdout
-    -- GHC does not guarantee to do this after TH code.  In particular
-    -- when the output is going to a file, and we're using GHC with
-    -- the runtime linker or with -fexternal-interpreter, stdout will
-    -- not get flushed.
+  mapM_ (runIO . hPutStrLn stderr . pprint) infos
+    -- NB. use stderr rather than stdout, because GHC does not
+    -- guarantee to flush stdout after TH code.  In particular when
+    -- the output is going to a file, and we're using GHC with the
+    -- runtime linker or with -fexternal-interpreter, stdout will not
+    -- get flushed.
   [d| theAnswerIs = 42 |]
diff --git a/testsuite/tests/th/T8761.stderr b/testsuite/tests/th/T8761.stderr
index 2ecf495e47..6a7af1e9e3 100644
--- a/testsuite/tests/th/T8761.stderr
+++ b/testsuite/tests/th/T8761.stderr
@@ -1,3 +1,7 @@
+pattern Q1 x1_0 x2_1 x3_2 <- ((x1_0, x2_1), [x3_2], _, _)
+pattern x1_0 Q2 x2_1 = ((x1_0, x2_1))
+pattern Q3 {qx3, qy3, qz3} <- ((qx3, qy3), [qz3]) where
+                                  Q3 qx3 qy3 qz3 = ((qx3, qy3), [qz3])
 T8761.hs:(16,1)-(39,13): Splicing declarations
     do { [qx1, qy1, qz1] <- mapM
                               (\ i -> newName $ "x" ++ show i) [1, 2, 3];
@@ -25,7 +29,7 @@ T8761.hs:(16,1)-(39,13): Splicing declarations
                = patSynD
                    nm3 (recordPatSyn [qx3, qy3, qz3]) (explBidir [cls]) patP;
          pats <- sequence [prefixPat, infixPat, recordPat];
-         mapM_ (runIO . putStrLn . pprint) pats;
+         mapM_ (runIO . hPutStrLn stderr . pprint) pats;
          return pats }
   ======>
     pattern Q1 x1 x2 x3 <- ((x1, x2), [x3], _, _)
@@ -119,10 +123,6 @@ T8761.hs:(71,1)-(105,39): Splicing declarations
     pattern Pup x <- MkUnivProv x
     pattern Puep :: forall a. forall b. Show b => a -> b -> (ExProv, a)
     pattern Puep x y <- (MkExProv y, x)
-pattern Q1 x1_0 x2_1 x3_2 <- ((x1_0, x2_1), [x3_2], _, _)
-pattern x1_0 Q2 x2_1 = ((x1_0, x2_1))
-pattern Q3 {qx3, qy3, qz3} <- ((qx3, qy3), [qz3]) where
-                                  Q3 qx3 qy3 qz3 = ((qx3, qy3), [qz3])
 pattern T8761.P :: GHC.Types.Bool
 pattern T8761.Pe :: () => forall (a0_0 :: *) . a0_0 -> T8761.Ex
 pattern T8761.Pu :: forall (a0_0 :: *) . a0_0 -> a0_0
@@ -152,8 +152,7 @@ T8761.hs:(108,1)-(117,25): Splicing declarations
                     reify
                     ['P, 'Pe, 'Pu, 'Pue, 'Pur, 'Purp, 'Pure, 'Purep, 'Pep, 'Pup,
                      'Puep];
-         mapM_ (runIO . putStrLn . pprint) infos;
-         runIO $ hFlush stdout;
+         mapM_ (runIO . hPutStrLn stderr . pprint) infos;
          [d| theAnswerIs = 42 |] }
   ======>
     theAnswerIs = 42