From 8deb1cd57c4badb0905051daaa0e8981583a4416 Mon Sep 17 00:00:00 2001
From: Kazu Yamamoto <kazu@iij.ad.jp>
Date: Mon, 13 Feb 2012 10:39:37 +0900
Subject: [PATCH] catching mutual module import.

---
 ErrMsg.hs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ErrMsg.hs b/ErrMsg.hs
index 7a858ad..95ddc79 100644
--- a/ErrMsg.hs
+++ b/ErrMsg.hs
@@ -57,10 +57,9 @@ ppErrMsg err = ppMsg spn msg defaultUserStyle ++ ext
 
 ppMsg :: SrcSpan -> Message -> PprStyle -> String
 #if __GLASGOW_HASKELL__ >= 702
-ppMsg (UnhelpfulSpan _) _ _   = undefined
 ppMsg (RealSrcSpan src) msg stl
 #else
-ppMsg src msg stl
+ppMsg src msg stl | isGoodSrcSpan src
 #endif
     = file ++ ":" ++ line ++ ":" ++ col ++ ":" ++ cts ++ "\0"
   where
@@ -68,12 +67,13 @@ ppMsg src msg stl
     line = show (srcSpanStartLine src)
     col  = show (srcSpanStartCol src)
     cts  = showMsg msg stl
+ppMsg _ _ _ = "ghc-mod:0:0:Probably mutual module import occurred\0"
 
 ----------------------------------------------------------------
 
 showMsg :: SDoc -> PprStyle -> String
 #if __GLASGOW_HASKELL__ >= 702
-showMsg d stl = map toNull $ renderWithStyle d stl
+showMsg d stl = map toNull . renderWithStyle d $ stl
 #else
 showMsg d stl = map toNull . Pretty.showDocWith PageMode $ d stl
 #endif