Restore old output for -ddump-rule-firings #7060

Commit 3fcf5bdff7a22e22d7265535369cd8f867141ec1 made the output of
-ddump-rule-firings and -ddump-rule-rewrites excessively verbose.

Fixed by removing the extra blank lines and separator when the header
of dump is empty.

2 files changed, 15 insertions, 11 deletions

diff --git a/compiler/main/ErrUtils.lhs b/compiler/main/ErrUtils.lhs
index daa66f9d2f..84722aa74a 100644
--- a/compiler/main/ErrUtils.lhs
+++ b/compiler/main/ErrUtils.lhs
@@ -251,8 +251,11 @@ dumpSDoc dflags dflag hdr doc
                         hClose handle
 
             -- write the dump to stdout
-            Nothing
-                 -> log_action dflags dflags SevDump noSrcSpan defaultDumpStyle (mkDumpDoc hdr doc)
+            Nothing -> do
+              let (doc', severity)
+                    | null hdr  = (doc, SevOutput)
+                    | otherwise = (mkDumpDoc hdr doc, SevDump)
+              log_action dflags dflags severity noSrcSpan defaultDumpStyle doc'
 
 
 -- | Choose where to put a dump file based on DynFlags
diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs
index df9013cd08..f2ed224df4 100644
--- a/compiler/simplCore/Simplify.lhs
+++ b/compiler/simplCore/Simplify.lhs
@@ -1571,21 +1571,22 @@ tryRules env rules fn args call_cont
   where
     trace_dump dflags rule rule_rhs
       | dopt Opt_D_dump_rule_rewrites dflags
-      = liftIO . dumpSDoc dflags Opt_D_dump_rule_rewrites "" $
-           vcat [text "Rule fired",
-                 text "Rule:" <+> ftext (ru_name rule),
-                 text "Before:" <+> hang (ppr fn) 2 (sep (map pprParendExpr args)),
-                 text "After: " <+> pprCoreExpr rule_rhs,
-                 text "Cont:  " <+> ppr call_cont]
+      = log_rule dflags Opt_D_dump_rule_rewrites "Rule fired" $ vcat
+          [ text "Rule:" <+> ftext (ru_name rule)
+          , text "Before:" <+> hang (ppr fn) 2 (sep (map pprParendExpr args))
+          , text "After: " <+> pprCoreExpr rule_rhs
+          , text "Cont:  " <+> ppr call_cont ]
 
       | dopt Opt_D_dump_rule_firings dflags
-      = liftIO . dumpSDoc dflags Opt_D_dump_rule_firings "" $
-          vcat [text "Rule fired",
-                ftext (ru_name rule)]
+      = log_rule dflags Opt_D_dump_rule_firings "Rule fired:" $
+          ftext (ru_name rule)
 
       | otherwise
       = return ()
 
+    log_rule dflags dflag hdr details = liftIO . dumpSDoc dflags dflag "" $
+      sep [text hdr, nest 4 details]
+
 \end{code}
 
 Note [Rules for recursive functions]