simplify the usage of IOChoice.

CabalApi.hs

@@ -33,7 +33,7 @@ fromCabalFile :: [GHCOption]
 fromCabalFile ghcOptions cradle = do
     cabal <- cabalParseFile cfile
     case cabalBuildInfo cabal of
-        Nothing    -> throwIO BrokenCabalFile
+        Nothing    -> throwIO $ userError "cabal file is broken"
         Just binfo -> return $ cookInfo ghcOptions cradle cabal binfo
   where
     Just cfile = cradleCabalFile cradle

Debug.hs

@@ -1,10 +1,8 @@
- {-# LANGUAGE TemplateHaskell #-}
-
 module Debug (debugInfo, debug) where
 
 import CabalApi
 import Control.Applicative
-import Control.Exception.IOChoice.TH
+import Control.Exception.IOChoice
 import Control.Monad
 import Data.List (intercalate)
 import Data.Maybe
@@ -15,11 +13,6 @@ import Types
 
 ----------------------------------------------------------------
 
-(||>>) :: IO a -> IO a -> IO a
-(||>>) = $(newIOChoice [''BrokenCabalFile])
-
-----------------------------------------------------------------
-
 debugInfo :: Options -> Cradle -> String -> String -> IO String
 debugInfo opt cradle ver fileName = unlines <$> debug opt cradle ver fileName
 
@@ -27,7 +20,7 @@ debug :: Options -> Cradle -> String -> String -> IO [String]
 debug opt cradle ver fileName = do
     (gopts, incDir, pkgs) <-
         if cabal then
-            fromCabalFile (ghcOpts opt) cradle ||>> return (ghcOpts opt, [], [])
+            fromCabalFile (ghcOpts opt) cradle ||> return (ghcOpts opt, [], [])
           else
             return (ghcOpts opt, [], [])
     [fast] <- withGHC fileName $ do

GHCApi.hs

@@ -22,6 +22,7 @@ import DynFlags
 import ErrMsg
 import Exception
 import GHC
+import GHCChoice
 import GHC.Paths (libdir)
 import System.Exit
 import System.IO
@@ -52,7 +53,7 @@ data Build = CabalPkg | SingleFile deriving Eq
 
 initializeFlagsWithCradle :: Options -> Cradle -> [GHCOption] -> Bool -> Ghc LogReader
 initializeFlagsWithCradle opt cradle ghcOptions logging
-  | cabal     = withCabal `gcatch` fallback
+  | cabal     = withCabal ||> withoutCabal
   | otherwise = withoutCabal
   where
     cabal = isJust $ cradleCabalFile cradle
@@ -61,8 +62,6 @@ initializeFlagsWithCradle opt cradle ghcOptions logging
         initSession CabalPkg opt gopts idirs (Just depPkgs) logging
     withoutCabal =
         initSession SingleFile opt ghcOptions importDirs Nothing logging
-    fallback :: BrokenCabalFile -> Ghc LogReader
-    fallback _ = withoutCabal
 
 ----------------------------------------------------------------
 

Types.hs

@@ -1,11 +1,7 @@
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE DeriveDataTypeable #-}
 
 module Types where
 
-import Control.Exception as E
-import Data.Typeable
-
 data OutputStyle = LispStyle | PlainStyle
 
 data Options = Options {
@@ -82,9 +78,3 @@ type IncludeDir = FilePath
 type Package    = String
 
 data CheckSpeed = Slow | Fast
-
-----------------------------------------------------------------
-
-data BrokenCabalFile = BrokenCabalFile deriving (Show, Typeable)
-
-instance Exception BrokenCabalFile