From f0bfcb88115bc1f78553aa4fbbcd25f3aadf7e05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Sat, 12 Jul 2014 11:16:16 +0200
Subject: [PATCH 1/5] Use GhcModT everywhere and remove the GhcMod alias

Not doing this makes having GhcModT pretty pointless as users of the
library wouldn't be able to use custom inner monads as evey function for
dealing with GhcModT's would be constraint to (GhcModT IO) thus only
allowing IO as the inner monad.
---
 Language/Haskell/GhcMod/Boot.hs      |  2 +-
 Language/Haskell/GhcMod/Browse.hs    | 15 ++++----
 Language/Haskell/GhcMod/CaseSplit.hs |  5 +--
 Language/Haskell/GhcMod/Check.hs     | 20 ++++++-----
 Language/Haskell/GhcMod/Convert.hs   |  2 +-
 Language/Haskell/GhcMod/Debug.hs     |  4 +--
 Language/Haskell/GhcMod/FillSig.hs   |  5 +--
 Language/Haskell/GhcMod/Find.hs      |  4 +--
 Language/Haskell/GhcMod/Flag.hs      |  2 +-
 Language/Haskell/GhcMod/Info.hs      | 10 +++---
 Language/Haskell/GhcMod/Lang.hs      |  2 +-
 Language/Haskell/GhcMod/Lint.hs      |  5 +--
 Language/Haskell/GhcMod/List.hs      |  2 +-
 Language/Haskell/GhcMod/Logger.hs    | 11 +++---
 Language/Haskell/GhcMod/Monad.hs     | 35 +++++++------------
 Language/Haskell/GhcMod/PkgDoc.hs    |  2 +-
 ghc-mod.cabal                        |  5 +++
 src/GHCMod.hs                        |  4 +--
 src/GHCModi.hs                       | 51 ++++++++++++++++------------
 test/TestUtils.hs                    | 12 ++++---
 20 files changed, 106 insertions(+), 92 deletions(-)

diff --git a/Language/Haskell/GhcMod/Boot.hs b/Language/Haskell/GhcMod/Boot.hs
index fd9345c..a95429c 100644
--- a/Language/Haskell/GhcMod/Boot.hs
+++ b/Language/Haskell/GhcMod/Boot.hs
@@ -8,7 +8,7 @@ import Language.Haskell.GhcMod.List
 import Language.Haskell.GhcMod.Monad
 
 -- | Printing necessary information for front-end booting.
-boot :: GhcMod String
+boot :: IOish m => GhcModT m String
 boot =  concat <$> sequence [modules, languages, flags,
                              concat <$> mapM browse preBrowsedModules]
 
diff --git a/Language/Haskell/GhcMod/Browse.hs b/Language/Haskell/GhcMod/Browse.hs
index 72419b8..aa0d1df 100644
--- a/Language/Haskell/GhcMod/Browse.hs
+++ b/Language/Haskell/GhcMod/Browse.hs
@@ -28,8 +28,9 @@ import Type (dropForAlls, splitFunTy_maybe, mkFunTy, isPredTy)
 -- | Getting functions, classes, etc from a module.
 --   If 'detailed' is 'True', their types are also obtained.
 --   If 'operators' is 'True', operators are also returned.
-browse :: ModuleString -- ^ A module name. (e.g. \"Data.List\")
-       -> GhcMod String
+browse :: IOish m
+       => ModuleString -- ^ A module name. (e.g. \"Data.List\")
+       -> GhcModT m String
 browse pkgmdl = convert' . sort =<< (listExports =<< getModule)
   where
     (mpkg,mdl) = splitPkgMdl pkgmdl
@@ -61,7 +62,7 @@ splitPkgMdl pkgmdl = case break (==':') pkgmdl of
     (mdl,"")    -> (Nothing,mdl)
     (pkg,_:mdl) -> (Just pkg,mdl)
 
-processExports :: ModuleInfo -> GhcMod [String]
+processExports :: IOish m => ModuleInfo -> GhcModT m [String]
 processExports minfo = do
   opt <- options
   let
@@ -70,13 +71,13 @@ processExports minfo = do
       | otherwise = filter (isAlpha . head . getOccString)
   mapM (showExport opt minfo) $ removeOps $ G.modInfoExports minfo
 
-showExport :: Options -> ModuleInfo -> Name -> GhcMod String
+showExport :: IOish m => Options -> ModuleInfo -> Name -> GhcModT m String
 showExport opt minfo e = do
   mtype' <- mtype
   return $ concat $ catMaybes [mqualified, Just $ formatOp $ getOccString e, mtype']
   where
     mqualified = (G.moduleNameString (G.moduleName $ G.nameModule e) ++ ".") `justIf` qualified opt
-    mtype :: GhcMod (Maybe String)
+    mtype :: IOish m => GhcModT m (Maybe String)
     mtype
       | detailed opt = do
         tyInfo <- G.modInfoLookupName minfo e
@@ -91,7 +92,7 @@ showExport opt minfo e = do
       | isAlpha n = nm
       | otherwise = "(" ++ nm ++ ")"
     formatOp "" = error "formatOp"
-    inOtherModule :: Name -> GhcMod (Maybe TyThing)
+    inOtherModule :: IOish m => Name -> GhcModT m (Maybe TyThing)
     inOtherModule nm = G.getModuleInfo (G.nameModule nm) >> G.lookupGlobalName nm
     justIf :: a -> Bool -> Maybe a
     justIf x True = Just x
@@ -138,7 +139,7 @@ showOutputable dflag = unwords . lines . showPage dflag styleUnqualified . ppr
 ----------------------------------------------------------------
 
 -- | Browsing all functions in all system/user modules.
-browseAll :: DynFlags -> GhcMod [(String,String)]
+browseAll :: IOish m => DynFlags -> GhcModT m [(String,String)]
 browseAll dflag = do
     ms <- G.packageDbModules True
     is <- mapM G.getModuleInfo ms
diff --git a/Language/Haskell/GhcMod/CaseSplit.hs b/Language/Haskell/GhcMod/CaseSplit.hs
index ce6faee..706d18d 100644
--- a/Language/Haskell/GhcMod/CaseSplit.hs
+++ b/Language/Haskell/GhcMod/CaseSplit.hs
@@ -33,10 +33,11 @@ data SplitToTextInfo = SplitToTextInfo { sVarName     :: String
                                        }
 
 -- | Splitting a variable in a equation.
-splits :: FilePath     -- ^ A target file.
+splits :: IOish m
+       => FilePath     -- ^ A target file.
        -> Int          -- ^ Line number.
        -> Int          -- ^ Column number.
-       -> GhcMod String
+       -> GhcModT m String
 splits file lineNo colNo = ghandle handler body
   where
     body = inModuleContext file $ \dflag style -> do
diff --git a/Language/Haskell/GhcMod/Check.hs b/Language/Haskell/GhcMod/Check.hs
index 736c42f..66c7b71 100644
--- a/Language/Haskell/GhcMod/Check.hs
+++ b/Language/Haskell/GhcMod/Check.hs
@@ -15,8 +15,9 @@ import Language.Haskell.GhcMod.Monad
 
 -- | Checking syntax of a target file using GHC.
 --   Warnings and errors are returned.
-checkSyntax :: [FilePath]  -- ^ The target files.
-            -> GhcMod String
+checkSyntax :: IOish m
+            => [FilePath]  -- ^ The target files.
+            -> GhcModT m String
 checkSyntax [] = return ""
 checkSyntax files = withErrorHandler sessionName $ do
     either id id <$> check files
@@ -29,8 +30,9 @@ checkSyntax files = withErrorHandler sessionName $ do
 
 -- | Checking syntax of a target file using GHC.
 --   Warnings and errors are returned.
-check :: [FilePath]  -- ^ The target files.
-      -> GhcMod (Either String String)
+check :: IOish m
+      => [FilePath]  -- ^ The target files.
+      -> GhcModT m (Either String String)
 check fileNames = do
   withLogger setAllWaringFlags $ do
     setTargetFiles fileNames
@@ -38,8 +40,9 @@ check fileNames = do
 ----------------------------------------------------------------
 
 -- | Expanding Haskell Template.
-expandTemplate :: [FilePath]  -- ^ The target files.
-               -> GhcMod String
+expandTemplate :: IOish m
+               => [FilePath]  -- ^ The target files.
+               -> GhcModT m String
 expandTemplate [] = return ""
 expandTemplate files = withErrorHandler sessionName $ do
     either id id <$> expand files
@@ -51,7 +54,8 @@ expandTemplate files = withErrorHandler sessionName $ do
 ----------------------------------------------------------------
 
 -- | Expanding Haskell Template.
-expand :: [FilePath]  -- ^ The target files.
-      -> GhcMod (Either String String)
+expand :: IOish m
+       => [FilePath]  -- ^ The target files.
+       -> GhcModT m (Either String String)
 expand fileNames = withLogger (Gap.setDumpSplices . setNoWaringFlags) $
     setTargetFiles fileNames
diff --git a/Language/Haskell/GhcMod/Convert.hs b/Language/Haskell/GhcMod/Convert.hs
index e348eca..ee1398b 100644
--- a/Language/Haskell/GhcMod/Convert.hs
+++ b/Language/Haskell/GhcMod/Convert.hs
@@ -23,7 +23,7 @@ inter :: Char -> [Builder] -> Builder
 inter _ [] = id
 inter c bs = foldr1 (\x y -> x . (c:) . y) bs
 
-convert' :: ToString a => a -> GhcMod String
+convert' :: (ToString a, IOish m) => a -> GhcModT m String
 convert' x = flip convert x <$> options
 
 convert :: ToString a => Options -> a -> String
diff --git a/Language/Haskell/GhcMod/Debug.hs b/Language/Haskell/GhcMod/Debug.hs
index 2278ad2..994411d 100644
--- a/Language/Haskell/GhcMod/Debug.hs
+++ b/Language/Haskell/GhcMod/Debug.hs
@@ -12,7 +12,7 @@ import Language.Haskell.GhcMod.Internal
 ----------------------------------------------------------------
 
 -- | Obtaining debug information.
-debugInfo :: GhcMod String
+debugInfo :: IOish m => GhcModT m String
 debugInfo = cradle >>= \c -> convert' =<< do
     CompilerOptions gopts incDir pkgs <-
         if isJust $ cradleCabalFile c then
@@ -38,5 +38,5 @@ debugInfo = cradle >>= \c -> convert' =<< do
 ----------------------------------------------------------------
 
 -- | Obtaining root information.
-rootInfo :: GhcMod String
+rootInfo :: IOish m => GhcModT m String
 rootInfo = convert' =<< cradleRootDir <$> cradle
diff --git a/Language/Haskell/GhcMod/FillSig.hs b/Language/Haskell/GhcMod/FillSig.hs
index 7cb2dc9..fc12384 100644
--- a/Language/Haskell/GhcMod/FillSig.hs
+++ b/Language/Haskell/GhcMod/FillSig.hs
@@ -38,10 +38,11 @@ data SigInfo = Signature SrcSpan [G.RdrName] (G.HsType G.RdrName)
 data HESigInfo = HESignature HE.SrcSpan [HE.Name HE.SrcSpanInfo] (HE.Type HE.SrcSpanInfo)
 
 -- | Create a initial body from a signature.
-sig :: FilePath     -- ^ A target file.
+sig :: IOish m
+    => FilePath     -- ^ A target file.
     -> Int          -- ^ Line number.
     -> Int          -- ^ Column number.
-    -> GhcMod String
+    -> GhcModT m String
 sig file lineNo colNo = ghandle handler body
   where
     body = inModuleContext file $ \dflag style -> do
diff --git a/Language/Haskell/GhcMod/Find.hs b/Language/Haskell/GhcMod/Find.hs
index 850d5df..d414e40 100644
--- a/Language/Haskell/GhcMod/Find.hs
+++ b/Language/Haskell/GhcMod/Find.hs
@@ -31,11 +31,11 @@ type Symbol = String
 newtype SymMdlDb = SymMdlDb (Map Symbol [ModuleString])
 
 -- | Finding modules to which the symbol belong.
-findSymbol :: Symbol -> GhcMod String
+findSymbol :: IOish m => Symbol -> GhcModT m String
 findSymbol sym = convert' =<< lookupSym sym <$> getSymMdlDb
 
 -- | Creating 'SymMdlDb'.
-getSymMdlDb :: GhcMod SymMdlDb
+getSymMdlDb :: IOish m => GhcModT m SymMdlDb
 getSymMdlDb = do
     sm <- G.getSessionDynFlags >>= browseAll
 #if MIN_VERSION_containers(0,5,0)
diff --git a/Language/Haskell/GhcMod/Flag.hs b/Language/Haskell/GhcMod/Flag.hs
index 74319e8..5fc3e2b 100644
--- a/Language/Haskell/GhcMod/Flag.hs
+++ b/Language/Haskell/GhcMod/Flag.hs
@@ -6,7 +6,7 @@ import Language.Haskell.GhcMod.Monad
 
 -- | Listing GHC flags. (e.g -fno-warn-orphans)
 
-flags :: GhcMod String
+flags :: IOish m => GhcModT m String
 flags = convert' [ "-f" ++ prefix ++ option
                  | option <- Gap.fOptions
                  , prefix <- ["","no-"]
diff --git a/Language/Haskell/GhcMod/Info.hs b/Language/Haskell/GhcMod/Info.hs
index 8b4afec..b58b53f 100644
--- a/Language/Haskell/GhcMod/Info.hs
+++ b/Language/Haskell/GhcMod/Info.hs
@@ -21,9 +21,10 @@ import Language.Haskell.GhcMod.Convert
 ----------------------------------------------------------------
 
 -- | Obtaining information of a target expression. (GHCi's info:)
-info :: FilePath     -- ^ A target file.
+info :: IOish m
+     => FilePath     -- ^ A target file.
      -> Expression   -- ^ A Haskell expression.
-     -> GhcMod String
+     -> GhcModT m String
 info file expr = do
     opt <- options
     convert opt <$> ghandle handler body
@@ -36,10 +37,11 @@ info file expr = do
 ----------------------------------------------------------------
 
 -- | Obtaining type of a target expression. (GHCi's type:)
-types :: FilePath     -- ^ A target file.
+types :: IOish m
+      => FilePath     -- ^ A target file.
       -> Int          -- ^ Line number.
       -> Int          -- ^ Column number.
-      -> GhcMod String
+      -> GhcModT m String
 types file lineNo colNo = do
     opt <- options
     convert opt <$> ghandle handler body
diff --git a/Language/Haskell/GhcMod/Lang.hs b/Language/Haskell/GhcMod/Lang.hs
index 071e178..badecbd 100644
--- a/Language/Haskell/GhcMod/Lang.hs
+++ b/Language/Haskell/GhcMod/Lang.hs
@@ -6,5 +6,5 @@ import Language.Haskell.GhcMod.Monad
 
 -- | Listing language extensions.
 
-languages :: GhcMod String
+languages :: IOish m => GhcModT m String
 languages = convert' supportedLanguagesAndExtensions
diff --git a/Language/Haskell/GhcMod/Lint.hs b/Language/Haskell/GhcMod/Lint.hs
index ede48c2..cfa915f 100644
--- a/Language/Haskell/GhcMod/Lint.hs
+++ b/Language/Haskell/GhcMod/Lint.hs
@@ -11,8 +11,9 @@ import Language.Haskell.HLint (hlint)
 
 -- | Checking syntax of a target file using hlint.
 --   Warnings and errors are returned.
-lint :: FilePath  -- ^ A target file.
-     -> GhcMod String
+lint :: IOish m
+     => FilePath  -- ^ A target file.
+     -> GhcModT m String
 lint file = do
   opt <- options
   ghandle handler . pack =<< (liftIO $ hlint $ file : "--quiet" : hlintOpts opt)
diff --git a/Language/Haskell/GhcMod/List.hs b/Language/Haskell/GhcMod/List.hs
index be0b4c7..ec93ae3 100644
--- a/Language/Haskell/GhcMod/List.hs
+++ b/Language/Haskell/GhcMod/List.hs
@@ -13,7 +13,7 @@ import UniqFM (eltsUFM)
 ----------------------------------------------------------------
 
 -- | Listing installed modules.
-modules :: GhcMod String
+modules :: IOish m => GhcModT m String
 modules = do
     opt <- options
     convert opt . (arrange opt) <$> (getModules `G.gcatch` handler)
diff --git a/Language/Haskell/GhcMod/Logger.hs b/Language/Haskell/GhcMod/Logger.hs
index 5d16788..2d7121e 100644
--- a/Language/Haskell/GhcMod/Logger.hs
+++ b/Language/Haskell/GhcMod/Logger.hs
@@ -34,7 +34,7 @@ newtype LogRef = LogRef (IORef Builder)
 newLogRef :: IO LogRef
 newLogRef = LogRef <$> newIORef id
 
-readAndClearLogRef :: LogRef -> GhcMod String
+readAndClearLogRef :: IOish m => LogRef -> GhcModT m String
 readAndClearLogRef (LogRef ref) = do
     b <- liftIO $ readIORef ref
     liftIO $ writeIORef ref id
@@ -50,9 +50,10 @@ appendLogRef df (LogRef ref) _ sev src style msg = do
 -- | Set the session flag (e.g. "-Wall" or "-w:") then
 --   executes a body. Logged messages are returned as 'String'.
 --   Right is success and Left is failure.
-withLogger :: (DynFlags -> DynFlags)
-           -> GhcMod ()
-           -> GhcMod (Either String String)
+withLogger :: IOish m
+           => (DynFlags -> DynFlags)
+           -> GhcModT m ()
+           -> GhcModT m (Either String String)
 withLogger setDF body = ghandle sourceError $ do
     logref <- liftIO $ newLogRef
     wflags <- filter ("-fno-warn" `isPrefixOf`) . ghcOpts <$> options
@@ -65,7 +66,7 @@ withLogger setDF body = ghandle sourceError $ do
 ----------------------------------------------------------------
 
 -- | Converting 'SourceError' to 'String'.
-sourceError :: SourceError -> GhcMod (Either String String)
+sourceError :: IOish m => SourceError -> GhcModT m (Either String String)
 sourceError err = do
     dflags <- G.getSessionDynFlags
     style <- toGhcMod getStyle
diff --git a/Language/Haskell/GhcMod/Monad.hs b/Language/Haskell/GhcMod/Monad.hs
index bf92caa..8b69921 100644
--- a/Language/Haskell/GhcMod/Monad.hs
+++ b/Language/Haskell/GhcMod/Monad.hs
@@ -4,13 +4,11 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Language.Haskell.GhcMod.Monad (
-   GhcMod
- , GhcModT
+   GhcModT
+ , IOish
  , GhcModEnv(..)
  , GhcModWriter
  , GhcModState(..)
- , runGhcMod'
- , runGhcMod
  , runGhcModT'
  , runGhcModT
  , newGhcModEnv
@@ -60,7 +58,8 @@ import Control.Monad.Base (MonadBase, liftBase)
 import Control.Monad.Reader.Class
 import Control.Monad.State.Class
 import Control.Monad.Trans.Class
-import Control.Monad.Trans.Control (MonadBaseControl(..), StM, liftBaseWith, control, liftBaseOp, liftBaseOp_)
+import Control.Monad.Trans.Control (MonadBaseControl(..), StM, liftBaseWith,
+  control, liftBaseOp, liftBaseOp_)
 import Control.Monad.Trans.RWS.Lazy (RWST(..), runRWST)
 import Control.Monad.Writer.Class
 
@@ -87,7 +86,7 @@ type GhcModWriter = ()
 
 ----------------------------------------------------------------
 
-type GhcMod a = GhcModT IO a
+type IOish m = (Functor m, MonadIO m, MonadBaseControl IO m)
 
 newtype GhcModT m a = GhcModT {
       unGhcModT :: RWST GhcModEnv GhcModWriter GhcModState m a
@@ -155,7 +154,7 @@ initSession build Options {..} CompilerOptions {..} = do
 
 ----------------------------------------------------------------
 
-runGhcModT' :: (MonadIO m, MonadBaseControl IO m)
+runGhcModT' :: IOish m
            => GhcModEnv
            -> GhcModState
            -> GhcModT m a
@@ -174,7 +173,7 @@ newGhcModEnv opt dir = do
         , gmCradle = c
         }
 
-runGhcModT :: (MonadIO m, MonadBaseControl IO m) => Options -> GhcModT m a -> m a
+runGhcModT :: IOish m => Options -> GhcModT m a -> m a
 runGhcModT opt action = do
     env <- liftBase $ newGhcModEnv opt =<< getCurrentDirectory
     (a,(_,_)) <- runGhcModT' env defaultState $ do
@@ -183,41 +182,31 @@ runGhcModT opt action = do
             initializeFlagsWithCradle opt (gmCradle env)
             action
     return a
-
-runGhcMod' :: GhcModEnv
-           -> GhcModState
-           -> GhcModT IO a
-           -> IO (a,(GhcModState, GhcModWriter))
-runGhcMod' = runGhcModT'
-
-runGhcMod :: Options -> GhcMod a -> IO a
-runGhcMod = runGhcModT
 ----------------------------------------------------------------
 
-withErrorHandler :: String -> GhcMod a -> GhcMod a
+withErrorHandler :: IOish m => String -> GhcModT m a -> GhcModT m a
 withErrorHandler label = ghandle ignore
   where
-    ignore :: SomeException -> GhcMod a
+    ignore :: IOish m => SomeException -> GhcModT m a
     ignore e = liftIO $ do
         hPutStr stderr $ label ++ ":0:0:Error:"
         hPrint stderr e
         exitSuccess
 
 -- | This is only a transitional mechanism don't use it for new code.
-toGhcMod :: (Functor m, MonadIO m) => Ghc a -> GhcModT m a
+toGhcMod :: IOish m => Ghc a -> GhcModT m a
 toGhcMod a = do
     s <- gmGhcSession <$> ask
     liftIO $ unGhc a $ Session s
 
 ----------------------------------------------------------------
 
-options :: GhcMod Options
+options :: IOish m => GhcModT m Options
 options = gmOptions <$> ask
 
-cradle :: GhcMod Cradle
+cradle :: IOish m => GhcModT m Cradle
 cradle = gmCradle <$> ask
 
-
 instance (MonadBaseControl IO m) => MonadBase IO (GhcModT m) where
     liftBase = GhcModT . liftBase
 
diff --git a/Language/Haskell/GhcMod/PkgDoc.hs b/Language/Haskell/GhcMod/PkgDoc.hs
index 02f882a..b29e172 100644
--- a/Language/Haskell/GhcMod/PkgDoc.hs
+++ b/Language/Haskell/GhcMod/PkgDoc.hs
@@ -9,7 +9,7 @@ import Control.Applicative ((<$>))
 import System.Process (readProcess)
 
 -- | Obtaining the package name and the doc path of a module.
-pkgDoc :: String -> GhcMod String
+pkgDoc :: IOish m => String -> GhcModT m String
 pkgDoc mdl = cradle >>= \c -> liftIO $ do
     pkg <- trim <$> readProcess "ghc-pkg" (toModuleOpts c) []
     if pkg == "" then
diff --git a/ghc-mod.cabal b/ghc-mod.cabal
index 8273417..f154bcb 100644
--- a/ghc-mod.cabal
+++ b/ghc-mod.cabal
@@ -51,6 +51,7 @@ Extra-Source-Files:     ChangeLog
 Library
   Default-Language:     Haskell2010
   GHC-Options:          -Wall
+  Extensions:           ConstraintKinds, FlexibleContexts
   Exposed-Modules:      Language.Haskell.GhcMod
                         Language.Haskell.GhcMod.Ghc
                         Language.Haskell.GhcMod.Monad
@@ -117,6 +118,7 @@ Executable ghc-mod
   Main-Is:              GHCMod.hs
   Other-Modules:        Paths_ghc_mod
   GHC-Options:          -Wall
+  Extensions:           ConstraintKinds, FlexibleContexts
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
                       , directory
@@ -130,6 +132,7 @@ Executable ghc-modi
   Main-Is:              GHCModi.hs
   Other-Modules:        Paths_ghc_mod
   GHC-Options:          -Wall
+  Extensions:           ConstraintKinds, FlexibleContexts
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
                       , containers
@@ -143,12 +146,14 @@ Test-Suite doctest
   Default-Language:     Haskell2010
   HS-Source-Dirs:       test
   Ghc-Options:          -threaded -Wall
+  Extensions:           ConstraintKinds, FlexibleContexts
   Main-Is:              doctests.hs
   Build-Depends:        base
                       , doctest >= 0.9.3
 
 Test-Suite spec
   Default-Language:     Haskell2010
+  Extensions:           ConstraintKinds, FlexibleContexts
   Main-Is:              Main.hs
   Hs-Source-Dirs:       test, .
   Type:                 exitcode-stdio-1.0
diff --git a/src/GHCMod.hs b/src/GHCMod.hs
index 2856a87..8424a3d 100644
--- a/src/GHCMod.hs
+++ b/src/GHCMod.hs
@@ -111,7 +111,7 @@ main = flip E.catches handlers $ do
         nArgs n f = if length remainingArgs == n
                         then f
                         else E.throw (ArgumentsMismatch cmdArg0)
-    res <- runGhcMod opt $ case cmdArg0 of
+    res <- runGhcModT opt $ case cmdArg0 of
       "list"    -> modules
       "lang"    -> languages
       "flag"    -> flags
@@ -152,7 +152,7 @@ main = flip E.catches handlers $ do
         hPutStrLn stderr $ "\"" ++ file ++ "\" not found"
         printUsage
     printUsage = hPutStrLn stderr $ '\n' : O.usageInfo usage argspec
-    withFile :: (FilePath -> GhcMod a) -> FilePath -> GhcMod a
+    withFile :: IOish m => (FilePath -> GhcModT m a) -> FilePath -> GhcModT m a
     withFile cmd file = do
         exist <- liftIO $ doesFileExist file
         if exist
diff --git a/src/GHCModi.hs b/src/GHCModi.hs
index 39449b4..d67a58d 100644
--- a/src/GHCModi.hs
+++ b/src/GHCModi.hs
@@ -101,8 +101,8 @@ main = E.handle cmdHandler $
 --            c = cradle0 { cradleCurrentDir = rootdir } TODO: ?????
         setCurrentDirectory rootdir
         mvar <- liftIO newEmptyMVar
-        void $ forkIO $ runGhcMod opt $ setupDB mvar
-        runGhcMod opt $ loop S.empty mvar
+        void $ forkIO $ runGhcModT opt $ setupDB mvar
+        runGhcModT opt $ loop S.empty mvar
       where
         -- this is just in case.
         -- If an error is caught here, it is a bug of GhcMod library.
@@ -116,7 +116,7 @@ replace (x:xs)    =  x  : replace xs
 
 ----------------------------------------------------------------
 
-setupDB :: MVar SymMdlDb -> GhcMod ()
+setupDB :: IOish m => MVar SymMdlDb -> GhcModT m ()
 setupDB mvar = ghandle handler $ do
     liftIO . putMVar mvar =<< getSymMdlDb
   where
@@ -124,7 +124,7 @@ setupDB mvar = ghandle handler $ do
 
 ----------------------------------------------------------------
 
-loop :: Set FilePath -> MVar SymMdlDb -> GhcMod ()
+loop :: IOish m => Set FilePath -> MVar SymMdlDb -> GhcModT m ()
 loop set mvar = do
     cmdArg <- liftIO getLine
     let (cmd,arg') = break (== ' ') cmdArg
@@ -152,9 +152,10 @@ loop set mvar = do
 
 ----------------------------------------------------------------
 
-checkStx :: Set FilePath
+checkStx :: IOish m
+         => Set FilePath
          -> FilePath
-         -> GhcMod (String, Bool, Set FilePath)
+         -> GhcModT m (String, Bool, Set FilePath)
 checkStx set file = do
     set' <- toGhcMod $ newFileSet set file
     let files = S.toList set'
@@ -191,17 +192,17 @@ isSameMainFile file (Just x)
 
 ----------------------------------------------------------------
 
-findSym :: Set FilePath -> String -> MVar SymMdlDb
-        -> GhcMod (String, Bool, Set FilePath)
+findSym :: IOish m => Set FilePath -> String -> MVar SymMdlDb
+        -> GhcModT m (String, Bool, Set FilePath)
 findSym set sym mvar = do
     db <- liftIO $ readMVar mvar
     opt <- options
     let ret = lookupSym' opt sym db
     return (ret, True, set)
 
-lintStx :: Set FilePath
+lintStx :: IOish m => Set FilePath
         -> FilePath
-        -> GhcMod (String, Bool, Set FilePath)
+        -> GhcModT m (String, Bool, Set FilePath)
 lintStx set optFile = do
     ret <- local env' $ lint file
     return (ret, True, set)
@@ -228,36 +229,40 @@ parseLintOptions optFile = case brk (== ']') (dropWhile (/= '[') optFile) of
 
 ----------------------------------------------------------------
 
-showInfo :: Set FilePath
+showInfo :: IOish m
+         => Set FilePath
          -> FilePath
-         -> GhcMod (String, Bool, Set FilePath)
+         -> GhcModT m (String, Bool, Set FilePath)
 showInfo set fileArg = do
     let [file, expr] = words fileArg
     set' <- newFileSet set file
     ret <- info file expr
     return (ret, True, set')
 
-showType :: Set FilePath
+showType :: IOish m
+         => Set FilePath
          -> FilePath
-         -> GhcMod (String, Bool, Set FilePath)
+         -> GhcModT m (String, Bool, Set FilePath)
 showType set fileArg  = do
     let [file, line, column] = words fileArg
     set' <- newFileSet set file
     ret <- types file (read line) (read column)
     return (ret, True, set')
 
-doSplit :: Set FilePath
+doSplit :: IOish m
+        => Set FilePath
         -> FilePath
-        -> GhcMod (String, Bool, Set FilePath)
+        -> GhcModT m (String, Bool, Set FilePath)
 doSplit set fileArg  = do
     let [file, line, column] = words fileArg
     set' <- newFileSet set file
     ret <- splits file (read line) (read column)
     return (ret, True, set')
 
-doSig :: Set FilePath
+doSig :: IOish m
+      => Set FilePath
       -> FilePath
-      -> GhcMod (String, Bool, Set FilePath)
+      -> GhcModT m (String, Bool, Set FilePath)
 doSig set fileArg  = do
     let [file, line, column] = words fileArg
     set' <- newFileSet set file
@@ -266,15 +271,17 @@ doSig set fileArg  = do
 
 ----------------------------------------------------------------
 
-bootIt :: Set FilePath
-       -> GhcMod (String, Bool, Set FilePath)
+bootIt :: IOish m
+       => Set FilePath
+       -> GhcModT m (String, Bool, Set FilePath)
 bootIt set = do
     ret <- boot
     return (ret, True, set)
 
-browseIt :: Set FilePath
+browseIt :: IOish m
+         => Set FilePath
          -> ModuleString
-         -> GhcMod (String, Bool, Set FilePath)
+         -> GhcModT m (String, Bool, Set FilePath)
 browseIt set mdl = do
     ret <- browse mdl
     return (ret, True, set)
diff --git a/test/TestUtils.hs b/test/TestUtils.hs
index acb6e21..c9ed00f 100644
--- a/test/TestUtils.hs
+++ b/test/TestUtils.hs
@@ -12,14 +12,14 @@ module TestUtils (
 import Language.Haskell.GhcMod.Monad
 import Language.Haskell.GhcMod.Types
 
-isolateCradle :: GhcMod a -> GhcMod a
+isolateCradle :: IOish m => GhcModT m a -> GhcModT m a
 isolateCradle action =
     local modifyEnv  $ action
  where
     modifyEnv e = e { gmCradle = (gmCradle e) { cradlePkgDbStack = [GlobalDb] } }
 
-runIsolatedGhcMod :: Options -> GhcMod a -> IO a
-runIsolatedGhcMod opt action = runGhcMod opt $ isolateCradle action
+runIsolatedGhcMod :: Options -> GhcModT IO a -> IO a
+runIsolatedGhcMod opt action = runGhcModT opt $ isolateCradle action
 
 -- | Run GhcMod in isolated cradle with default options
 runID = runIsolatedGhcMod defaultOptions
@@ -28,7 +28,9 @@ runID = runIsolatedGhcMod defaultOptions
 runI = runIsolatedGhcMod
 
 -- | Run GhcMod
-run = runGhcMod
+run :: Options -> GhcModT IO a -> IO a
+run = runGhcModT
 
 -- | Run GhcMod with default options
-runD = runGhcMod defaultOptions
+runD :: GhcModT IO a -> IO a
+runD = runGhcModT defaultOptions

From 0a62ad911601277a9e93f7fff9d60ba09e881db8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Mon, 14 Jul 2014 16:54:49 +0200
Subject: [PATCH 2/5] Fix doctest

---
 test/doctests.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test/doctests.hs b/test/doctests.hs
index 8bf21ed..b860d45 100644
--- a/test/doctests.hs
+++ b/test/doctests.hs
@@ -6,6 +6,7 @@ main :: IO ()
 main = doctest [
     "-package"
   , "ghc"
+  , "-XConstraintKinds", "-XFlexibleContexts"
   , "-idist/build/autogen/"
   , "-optP-include"
   , "-optPdist/build/autogen/cabal_macros.h"

From 7474a1b652a73930aca8bf95e96457cee11a3672 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Tue, 15 Jul 2014 00:51:22 +0200
Subject: [PATCH 3/5] Bring back `GhcMod` but this time it's a GhcModT with an
 ErrorT inside

---
 Language/Haskell/GhcMod/Monad.hs | 72 ++++++++++++++++++++++++++------
 1 file changed, 60 insertions(+), 12 deletions(-)

diff --git a/Language/Haskell/GhcMod/Monad.hs b/Language/Haskell/GhcMod/Monad.hs
index 8b69921..960e5c6 100644
--- a/Language/Haskell/GhcMod/Monad.hs
+++ b/Language/Haskell/GhcMod/Monad.hs
@@ -1,10 +1,14 @@
 {-# LANGUAGE CPP, GeneralizedNewtypeDeriving, FlexibleInstances #-}
 {-# LANGUAGE FlexibleContexts, MultiParamTypeClasses, RankNTypes #-}
 {-# LANGUAGE TypeFamilies, UndecidableInstances, RecordWildCards #-}
+{-# LANGUAGE StandaloneDeriving #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Language.Haskell.GhcMod.Monad (
-   GhcModT
+   GhcMod
+ , runGhcMod
+ , liftGhcMod
+ , GhcModT
  , IOish
  , GhcModEnv(..)
  , GhcModWriter
@@ -16,6 +20,8 @@ module Language.Haskell.GhcMod.Monad (
  , toGhcMod
  , options
  , cradle
+ , Options(..)
+ , defaultOptions
  , module Control.Monad.Reader.Class
  , module Control.Monad.Writer.Class
  , module Control.Monad.State.Class
@@ -54,6 +60,7 @@ import Data.Monoid (Monoid)
 import Control.Applicative (Alternative)
 import Control.Monad (MonadPlus, liftM, void)
 import Control.Monad.Base (MonadBase, liftBase)
+import Control.Monad.Trans.RWS.Lazy (liftCatch)
 
 import Control.Monad.Reader.Class
 import Control.Monad.State.Class
@@ -62,6 +69,7 @@ import Control.Monad.Trans.Control (MonadBaseControl(..), StM, liftBaseWith,
   control, liftBaseOp, liftBaseOp_)
 import Control.Monad.Trans.RWS.Lazy (RWST(..), runRWST)
 import Control.Monad.Writer.Class
+import Control.Monad.Error
 
 import Data.Maybe (fromJust, isJust)
 import Data.IORef (IORef, readIORef, writeIORef, newIORef)
@@ -77,17 +85,29 @@ data GhcModEnv = GhcModEnv {
     , gmCradle     :: Cradle
     }
 
-data GhcModState = GhcModState
+data GhcModState = GhcModState deriving (Eq,Show,Read)
 
 defaultState :: GhcModState
 defaultState = GhcModState
 
 type GhcModWriter = ()
 
+data GhcModError = GMENoMsg
+                 | GMEString String
+                 | GMECabal
+                 | GMEGhc
+                   deriving (Eq,Show,Read)
+
+instance Error GhcModError where
+    noMsg = GMENoMsg
+    strMsg = GMEString
+
 ----------------------------------------------------------------
 
 type IOish m = (Functor m, MonadIO m, MonadBaseControl IO m)
 
+type GhcMod a = GhcModT (ErrorT GhcModError IO) a
+
 newtype GhcModT m a = GhcModT {
       unGhcModT :: RWST GhcModEnv GhcModWriter GhcModState m a
     } deriving (Functor
@@ -102,6 +122,8 @@ newtype GhcModT m a = GhcModT {
                , MonadTrans
                )
 
+deriving instance MonadError GhcModError m => MonadError GhcModError (GhcModT m)
+
 #if __GLASGOW_HASKELL__ < 708
 instance (Monoid w, MonadIO m) => MonadIO (RWST r w s m) where
 --  liftIO :: MonadIO m => IO a -> m a
@@ -154,15 +176,6 @@ initSession build Options {..} CompilerOptions {..} = do
 
 ----------------------------------------------------------------
 
-runGhcModT' :: IOish m
-           => GhcModEnv
-           -> GhcModState
-           -> GhcModT m a
-           -> m (a,(GhcModState, GhcModWriter))
-runGhcModT' r s a = do
-  (a',s',w) <- runRWST (unGhcModT $ initGhcMonad (Just libdir) >> a) r s
-  return (a',(s',w))
-
 newGhcModEnv :: Options -> FilePath -> IO GhcModEnv
 newGhcModEnv opt dir = do
       session <- newIORef (error "empty session")
@@ -173,6 +186,9 @@ newGhcModEnv opt dir = do
         , gmCradle = c
         }
 
+-- | Run a @GhcModT m@ computation, i.e. one with a custom underlying monad.
+--
+-- You probably don't want this, look at 'runGhcMod' instead.
 runGhcModT :: IOish m => Options -> GhcModT m a -> m a
 runGhcModT opt action = do
     env <- liftBase $ newGhcModEnv opt =<< getCurrentDirectory
@@ -182,6 +198,38 @@ runGhcModT opt action = do
             initializeFlagsWithCradle opt (gmCradle env)
             action
     return a
+
+-- | Run a computation inside @GhcModT@ providing the RWST environment and
+-- initial state. This is a low level function, use it only if you know what to
+-- do with 'GhcModEnv' and 'GhcModState'.
+--
+-- You should probably look at 'runGhcModT' instead.
+runGhcModT' :: IOish m
+           => GhcModEnv
+           -> GhcModState
+           -> GhcModT m a
+           -> m (a,(GhcModState, GhcModWriter))
+runGhcModT' r s a = do
+  (a',s',w) <- runRWST (unGhcModT $ initGhcMonad (Just libdir) >> a) r s
+  return (a',(s',w))
+
+-- | Run a 'GhcMod' computation. If you want an underlying monad other than
+-- 'ErrorT e IO' you should look at 'runGhcModT'
+runGhcMod :: Options
+          -> GhcMod a
+          -> IO (Either GhcModError a)
+runGhcMod o a =
+  runErrorT $ runGhcModT o a
+
+liftErrorT :: IOish m => GhcModT m a -> GhcModT (ErrorT GhcModError m) a
+liftErrorT action =
+    GhcModT $ RWST $ \e s -> ErrorT $ Right <$> (runRWST $ unGhcModT action) e s
+
+-- | Lift @(GhcModT IO)@ into @GhcMod@, which is an alias for @GhcModT (ErrorT
+-- GhcModError IO)@.
+liftGhcMod :: GhcModT IO a -> GhcMod a
+liftGhcMod = liftErrorT
+
 ----------------------------------------------------------------
 
 withErrorHandler :: IOish m => String -> GhcModT m a -> GhcModT m a
@@ -212,7 +260,7 @@ instance (MonadBaseControl IO m) => MonadBase IO (GhcModT m) where
 
 instance (MonadBaseControl IO m) => MonadBaseControl IO (GhcModT m) where
     newtype StM (GhcModT m) a = StGhcMod {
-          unStGhcMod :: StM (RWST GhcModEnv () GhcModState m) a }
+          unStGhcMod :: StM (RWST GhcModEnv GhcModWriter GhcModState m) a }
 
     liftBaseWith f = GhcModT . liftBaseWith $ \runInBase ->
         f $ liftM StGhcMod . runInBase . unGhcModT

From 68212d46a1c29952cf07a324859a602adbcbac48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Tue, 15 Jul 2014 01:53:06 +0200
Subject: [PATCH 4/5] Fix cabal file

---
 ghc-mod.cabal | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/ghc-mod.cabal b/ghc-mod.cabal
index f154bcb..e357b51 100644
--- a/ghc-mod.cabal
+++ b/ghc-mod.cabal
@@ -51,7 +51,7 @@ Extra-Source-Files:     ChangeLog
 Library
   Default-Language:     Haskell2010
   GHC-Options:          -Wall
-  Extensions:           ConstraintKinds, FlexibleContexts
+  Default-Extensions:   ConstraintKinds, FlexibleContexts
   Exposed-Modules:      Language.Haskell.GhcMod
                         Language.Haskell.GhcMod.Ghc
                         Language.Haskell.GhcMod.Monad
@@ -118,7 +118,7 @@ Executable ghc-mod
   Main-Is:              GHCMod.hs
   Other-Modules:        Paths_ghc_mod
   GHC-Options:          -Wall
-  Extensions:           ConstraintKinds, FlexibleContexts
+  Default-Extensions:   ConstraintKinds, FlexibleContexts
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
                       , directory
@@ -132,7 +132,7 @@ Executable ghc-modi
   Main-Is:              GHCModi.hs
   Other-Modules:        Paths_ghc_mod
   GHC-Options:          -Wall
-  Extensions:           ConstraintKinds, FlexibleContexts
+  Default-Extensions:   ConstraintKinds, FlexibleContexts
   HS-Source-Dirs:       src
   Build-Depends:        base >= 4.0 && < 5
                       , containers
@@ -146,14 +146,14 @@ Test-Suite doctest
   Default-Language:     Haskell2010
   HS-Source-Dirs:       test
   Ghc-Options:          -threaded -Wall
-  Extensions:           ConstraintKinds, FlexibleContexts
+  Default-Extensions:   ConstraintKinds, FlexibleContexts
   Main-Is:              doctests.hs
   Build-Depends:        base
                       , doctest >= 0.9.3
 
 Test-Suite spec
   Default-Language:     Haskell2010
-  Extensions:           ConstraintKinds, FlexibleContexts
+  Default-Extensions:   ConstraintKinds, FlexibleContexts
   Main-Is:              Main.hs
   Hs-Source-Dirs:       test, .
   Type:                 exitcode-stdio-1.0

From 686179f12b87387ffb6d1b5fc007516d886e729c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gr=C3=B6ber?= <dxld@darkboxed.org>
Date: Tue, 15 Jul 2014 02:34:07 +0200
Subject: [PATCH 5/5] Fix building with ghc < 7.8

---
 Language/Haskell/GhcMod/Monad.hs | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/Language/Haskell/GhcMod/Monad.hs b/Language/Haskell/GhcMod/Monad.hs
index 960e5c6..f00bb69 100644
--- a/Language/Haskell/GhcMod/Monad.hs
+++ b/Language/Haskell/GhcMod/Monad.hs
@@ -27,6 +27,16 @@ module Language.Haskell.GhcMod.Monad (
  , module Control.Monad.State.Class
  ) where
 
+#if __GLASGOW_HASKELL__ < 708
+-- 'CoreMonad.MonadIO' and 'Control.Monad.IO.Class.MonadIO' are different
+-- classes before ghc 7.8
+#define DIFFERENT_MONADIO 1
+
+-- RWST doen't have a MonadIO instance before ghc 7.8
+#define MONADIO_INSTANCES 1
+#endif
+
+
 import Language.Haskell.GhcMod.Types
 import Language.Haskell.GhcMod.Cradle
 import Language.Haskell.GhcMod.DynFlags
@@ -51,9 +61,9 @@ import HscTypes
 -- So, RWST automatically becomes an instance of MonadIO.
 import MonadUtils
 
-#if __GLASGOW_HASKELL__ < 708
--- To make RWST an instance of MonadIO.
+#if DIFFERENT_MONADIO
 import Control.Monad.Trans.Class (lift)
+import qualified Control.Monad.IO.Class
 import Data.Monoid (Monoid)
 #endif
 
@@ -65,11 +75,12 @@ import Control.Monad.Trans.RWS.Lazy (liftCatch)
 import Control.Monad.Reader.Class
 import Control.Monad.State.Class
 import Control.Monad.Trans.Class
+import Control.Monad.Trans.Maybe
 import Control.Monad.Trans.Control (MonadBaseControl(..), StM, liftBaseWith,
   control, liftBaseOp, liftBaseOp_)
 import Control.Monad.Trans.RWS.Lazy (RWST(..), runRWST)
 import Control.Monad.Writer.Class
-import Control.Monad.Error
+import Control.Monad.Error (Error(..), ErrorT(..), MonadError)
 
 import Data.Maybe (fromJust, isJust)
 import Data.IORef (IORef, readIORef, writeIORef, newIORef)
@@ -116,6 +127,9 @@ newtype GhcModT m a = GhcModT {
                , Monad
                , MonadPlus
                , MonadIO
+#if DIFFERENT_MONADIO
+               , Control.Monad.IO.Class.MonadIO
+#endif
                , MonadReader GhcModEnv
                , MonadWriter GhcModWriter
                , MonadState GhcModState
@@ -124,10 +138,16 @@ newtype GhcModT m a = GhcModT {
 
 deriving instance MonadError GhcModError m => MonadError GhcModError (GhcModT m)
 
-#if __GLASGOW_HASKELL__ < 708
+#if MONADIO_INSTANCES
 instance (Monoid w, MonadIO m) => MonadIO (RWST r w s m) where
---  liftIO :: MonadIO m => IO a -> m a
     liftIO = lift . liftIO
+
+instance (Error e, MonadIO m) => MonadIO (ErrorT e m) where
+    liftIO = lift . liftIO
+
+instance (MonadIO m) => MonadIO (MaybeT m) where
+    liftIO = lift . liftIO
+
 #endif
 
 ----------------------------------------------------------------