NG contains an error.

Language/Haskell/GhcMod/ErrMsg.hs

@@ -4,6 +4,7 @@ module Language.Haskell.GhcMod.ErrMsg (
     LogReader
   , setLogger
   , handleErrMsg
+  , checkErrorPrefix
   ) where
 
 import Bag (Bag, bagToList)
@@ -85,9 +86,12 @@ ppMsg spn sev dflag style msg = prefix ++ cts
     cts  = showPage dflag style msg
     defaultPrefix
       | dopt Gap.dumpSplicesFlag dflag = ""
-      | otherwise                      = "Dummy:0:0:Error:"
+      | otherwise                      = checkErrorPrefix
     prefix = fromMaybe defaultPrefix $ do
         (line,col,_,_) <- Gap.getSrcSpan spn
         file <- normalise <$> Gap.getSrcFile spn
         let severityCaption = Gap.showSeverityCaption sev
         return $ file ++ ":" ++ show line ++ ":" ++ show col ++ ":" ++ severityCaption
+
+checkErrorPrefix :: String
+checkErrorPrefix = "Dummy:0:0:Error:"

Language/Haskell/GhcMod/Lint.hs

@@ -1,6 +1,8 @@
 module Language.Haskell.GhcMod.Lint where
 
 import Control.Applicative ((<$>))
+import Control.Exception (handle, SomeException(..))
+import Language.Haskell.GhcMod.ErrMsg (checkErrorPrefix)
 import Language.Haskell.GhcMod.Types
 import Language.Haskell.HLint (hlint)
 
@@ -9,7 +11,8 @@ import Language.Haskell.HLint (hlint)
 lintSyntax :: Options
            -> FilePath  -- ^ A target file.
            -> IO String
-lintSyntax opt file = pack <$> hlint (file : "--quiet" : hopts)
+lintSyntax opt file = handle handler $ pack <$> hlint (file : "--quiet" : hopts)
   where
     pack = convert opt . map (init . show) -- init drops the last \n.
     hopts = hlintOpts opt
+    handler (SomeException e) = return $ checkErrorPrefix ++ show e ++ "\n"