Merge branch 'master' of https://github.com/GrammaticalFramework/gf-core

src/compiler/GF/Command/Commands.hs

@@ -34,6 +34,7 @@ import Data.Maybe
 import qualified Data.Map as Map
 import GF.Text.Pretty
 import Data.List (sort)
+import qualified Control.Monad.Fail as Fail
 --import Debug.Trace
 
 
@@ -44,7 +45,7 @@ pgfEnv pgf = Env pgf mos
 
 class (Functor m,Monad m,MonadSIO m) => HasPGFEnv m where getPGFEnv :: m PGFEnv
 
-instance (Monad m,HasPGFEnv m) => TypeCheckArg m where
+instance (Monad m,HasPGFEnv m,Fail.MonadFail m) => TypeCheckArg m where
   typeCheckArg e = (either (fail . render . ppTcError) (return . fst)
                     . flip inferExpr e . pgf) =<< getPGFEnv
 

src/compiler/GF/Command/Commands2.hs

@@ -18,6 +18,7 @@ import Data.Maybe
 import qualified Data.Map as Map
 import GF.Text.Pretty
 import Control.Monad(mplus)
+import qualified Control.Monad.Fail as Fail
 
 
 data PGFEnv = Env {pgf::Maybe PGF,concs::Map.Map ConcName Concr}
@@ -25,7 +26,7 @@ data PGFEnv = Env {pgf::Maybe PGF,concs::Map.Map ConcName Concr}
 pgfEnv pgf = Env (Just pgf) (languages pgf)
 emptyPGFEnv = Env Nothing Map.empty
 
-class (Monad m,MonadSIO m) => HasPGFEnv m where getPGFEnv :: m PGFEnv
+class (Fail.MonadFail m,MonadSIO m) => HasPGFEnv m where getPGFEnv :: m PGFEnv
 
 instance (Monad m,HasPGFEnv m) => TypeCheckArg m where
   typeCheckArg e = do env <- getPGFEnv

src/compiler/GF/Command/Interpreter.hs

@@ -11,6 +11,8 @@ import GF.Infra.UseIO(putStrLnE)
 
 import Control.Monad(when)
 import qualified Data.Map as Map
+import GF.Infra.UseIO (Output)
+import qualified Control.Monad.Fail as Fail
 
 data CommandEnv m = CommandEnv {
   commands      :: Map.Map String (CommandInfo m),
@@ -22,6 +24,7 @@ data CommandEnv m = CommandEnv {
 mkCommandEnv cmds = CommandEnv cmds Map.empty Map.empty
 
 --interpretCommandLine :: CommandEnv -> String -> SIO ()
+interpretCommandLine :: (Fail.MonadFail m, Output m, TypeCheckArg m) => CommandEnv m -> String -> m ()
 interpretCommandLine env line =
   case readCommandLine line of
     Just []    -> return ()

src/compiler/GF/Compile/GeneratePMCFG.hs

@@ -41,6 +41,7 @@ import Control.Monad
 import Control.Monad.Identity
 --import Control.Exception
 --import Debug.Trace(trace)
+import qualified Control.Monad.Fail as Fail
 
 ----------------------------------------------------------------------
 -- main conversion function
@@ -196,6 +197,9 @@ newtype CnvMonad a = CM {unCM :: SourceGrammar
                               -> ([ProtoFCat],[Symbol])
                               -> Branch b}
 
+instance Fail.MonadFail CnvMonad where
+  fail = bug
+
 instance Applicative CnvMonad where
   pure = return
   (<*>) = ap

src/compiler/GF/Compile/TypeCheck/ConcreteNew.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 module GF.Compile.TypeCheck.ConcreteNew( checkLType, inferLType ) where
 
 -- The code here is based on the paper:
@@ -19,6 +20,7 @@ import GF.Text.Pretty
 import Data.List (nub, (\\), tails)
 import qualified Data.IntMap as IntMap
 import Data.Maybe(fromMaybe,isNothing)
+import qualified Control.Monad.Fail as Fail
 
 checkLType :: GlobalEnv -> Term -> Type -> Check (Term, Type)
 checkLType ge t ty = runTcM $ do
@@ -646,8 +648,16 @@ instance Monad TcM where
   f >>= g  = TcM (\ms msgs -> case unTcM f ms msgs of
                                 TcOk x ms msgs -> unTcM (g x) ms msgs
                                 TcFail    msgs -> TcFail msgs)
+
+#if !(MIN_VERSION_base(4,13,0))
+  -- Monad(fail) will be removed in GHC 8.8+
+  fail = Fail.fail
+#endif
+
+instance Fail.MonadFail TcM where
   fail     = tcError . pp
 
+
 instance Applicative TcM where
   pure = return
   (<*>) = ap

src/compiler/GF/Compile/Update.hs

@@ -27,9 +27,10 @@ import Data.List
 import qualified Data.Map as Map
 import Control.Monad
 import GF.Text.Pretty
+import qualified Control.Monad.Fail as Fail
 
 -- | combine a list of definitions into a balanced binary search tree
-buildAnyTree :: Monad m => ModuleName -> [(Ident,Info)] -> m (Map.Map Ident Info)
+buildAnyTree :: Fail.MonadFail m => ModuleName -> [(Ident,Info)] -> m (Map.Map Ident Info)
 buildAnyTree m = go Map.empty
   where
     go map []         = return map

src/compiler/GF/CompileInParallel.hs

@@ -20,6 +20,8 @@ import GF.Infra.Ident(moduleNameS)
 import GF.Text.Pretty
 import GF.System.Console(TermColors(..),getTermColors)
 import qualified Data.ByteString.Lazy as BS
+-- Control.Monad.Fail import will become redundant in GHC 8.8+
+import qualified Control.Monad.Fail as Fail
 
 -- | Compile the given grammar files and everything they depend on,
 -- like 'batchCompile'. This function compiles modules in parallel.
@@ -256,6 +258,9 @@ instance Output m => Output (CollectOutput m) where
   putStrLnE s = CO (return (putStrLnE s,()))
   putStrE   s = CO (return (putStrE s,()))
 
+instance Fail.MonadFail m => Fail.MonadFail (CollectOutput m) where
+  fail = CO . fail
+
 instance ErrorMonad m => ErrorMonad (CollectOutput m) where
   raise e = CO (raise e)
   handle (CO m) h = CO $ handle m (unCO . h)

src/compiler/GF/CompileOne.hs

@@ -30,12 +30,13 @@ import qualified Data.Map as Map
 import GF.Text.Pretty(render,(<+>),($$)) --Doc,
 import GF.System.Console(TermColors(..),getTermColors)
 import Control.Monad((<=<))
+import qualified Control.Monad.Fail as Fail
 
 type OneOutput = (Maybe FullPath,CompiledModule)
 type CompiledModule = Module
 
 compileOne, reuseGFO, useTheSource ::
-    (Output m,ErrorMonad m,MonadIO m) =>
+    (Output m,ErrorMonad m,MonadIO m, Fail.MonadFail m) =>
     Options -> Grammar -> FullPath -> m OneOutput
 
 -- | Compile a given source file (or just load a .gfo file),

src/compiler/GF/Data/BacktrackM.hs

@@ -13,6 +13,7 @@
 -----------------------------------------------------------------------------
 
 {-# LANGUAGE Rank2Types, MultiParamTypeClasses, FlexibleInstances #-}
+{-# LANGUAGE CPP #-}
 module GF.Data.BacktrackM (
                     -- * the backtracking state monad
 		    BacktrackM,
@@ -32,6 +33,7 @@ import Data.List
 import Control.Applicative
 import Control.Monad
 import Control.Monad.State.Class
+import qualified Control.Monad.Fail as Fail
 
 ----------------------------------------------------------------------
 -- Combining endomorphisms and continuations
@@ -69,6 +71,12 @@ instance Monad (BacktrackM s) where
     return a   = BM (\c s b -> c a s b)
     BM m >>= k = BM (\c s b -> m (\a s b -> unBM (k a) c s b) s b)
 	where unBM (BM m) = m
+
+#if !(MIN_VERSION_base(4,13,0))
+    fail = Fail.fail
+#endif
+
+instance Fail.MonadFail (BacktrackM s) where
     fail _ = mzero
 
 instance Functor (BacktrackM s) where

src/compiler/GF/Data/ErrM.hs

@@ -12,10 +12,12 @@
 -- hack for BNFC generated files. AR 21/9/2003
 -----------------------------------------------------------------------------
 
+{-# LANGUAGE CPP #-}
 module GF.Data.ErrM where
 
 import Control.Monad (MonadPlus(..),ap)
 import Control.Applicative
+import qualified Control.Monad.Fail as Fail
 
 -- | Like 'Maybe' type with error msgs
 data Err a = Ok a | Bad String
@@ -33,10 +35,19 @@ fromErr a = err (const a) id
 
 instance Monad Err where
   return      = Ok
-  fail        = Bad
   Ok a  >>= f = f a
   Bad s >>= f = Bad s
 
+#if !(MIN_VERSION_base(4,13,0))
+  -- Monad(fail) will be removed in GHC 8.8+
+  fail = Fail.fail
+#endif
+
+instance Fail.MonadFail Err where
+  fail        = Bad
+
+
+
 -- | added 2\/10\/2003 by PEB
 instance Functor Err where
   fmap f (Ok a) = Ok (f a)

src/compiler/GF/Data/Operations.hs

@@ -53,6 +53,7 @@ import Control.Monad (liftM,liftM2) --,ap
 
 import GF.Data.ErrM
 import GF.Data.Relation
+import qualified Control.Monad.Fail as Fail
 
 infixr 5 +++
 infixr 5 ++-
@@ -88,10 +89,10 @@ checkUnique ss = ["overloaded" +++ show s | s <- nub overloads] where
   overloaded s = length (filter (==s) ss) > 1
 
 -- | this is what happens when matching two values in the same module
-unifyMaybe :: (Eq a, Monad m) => Maybe a -> Maybe a -> m (Maybe a)
+unifyMaybe :: (Eq a, Fail.MonadFail m) => Maybe a -> Maybe a -> m (Maybe a)
 unifyMaybe = unifyMaybeBy id
 
-unifyMaybeBy :: (Eq b, Monad m) => (a->b) -> Maybe a -> Maybe a -> m (Maybe a)
+unifyMaybeBy :: (Eq b, Fail.MonadFail m) => (a->b) -> Maybe a -> Maybe a -> m (Maybe a)
 unifyMaybeBy f (Just p1) (Just p2)
   | f p1==f p2                     = return (Just p1)
   | otherwise                      = fail ""

src/compiler/GF/Grammar/CanonicalJSON.hs

@@ -6,6 +6,7 @@ import Text.JSON
 import Control.Applicative ((<|>))
 import Data.Ratio (denominator, numerator)
 import GF.Grammar.Canonical
+import Control.Monad (guard)
 
 
 encodeJSON :: FilePath -> Grammar -> IO ()
@@ -126,10 +127,10 @@ instance JSON LinType where
   -- records are encoded as records:
   showJSON (RecordType rows) = showJSON rows
 
-  readJSON o = do "Str"   <- readJSON o; return StrType
-    <|>        do "Float" <- readJSON o; return FloatType
-    <|>        do "Int"   <- readJSON o; return IntType
-    <|>        do  ptype  <- readJSON o; return (ParamType ptype)
+  readJSON o = StrType   <$ parseString "Str"   o
+    <|>        FloatType <$ parseString "Float" o
+    <|>        IntType   <$ parseString "Int"   o
+    <|>        ParamType <$> readJSON o
     <|>        TableType  <$> o!".tblarg" <*> o!".tblval"
     <|>        TupleType  <$> o!".tuple"
     <|>        RecordType <$> readJSON o
@@ -186,7 +187,7 @@ instance JSON LinPattern where
   -- and records as records:
   showJSON (RecordPattern r) = showJSON r
 
-  readJSON o = do "_" <- readJSON o; return WildPattern
+  readJSON o = do  p  <- parseString "_" o; return WildPattern
     <|>        do  p  <- readJSON o; return (ParamPattern (Param p []))
     <|>        ParamPattern  <$> readJSON o
     <|>        RecordPattern <$> readJSON o
@@ -237,7 +238,7 @@ instance JSON VarId where
   showJSON Anonymous = showJSON "_"
   showJSON (VarId x) = showJSON x
 
-  readJSON o = do "_" <- readJSON o; return Anonymous
+  readJSON o = do parseString "_" o; return Anonymous
     <|>        VarId <$> readJSON o
 
 instance JSON QualId where
@@ -268,6 +269,9 @@ instance JSON FlagValue where
 --------------------------------------------------------------------------------
 -- ** Convenience functions
 
+parseString :: String -> JSValue -> Result ()
+parseString s o = guard . (== s) =<< readJSON o
+
 (!) :: JSON a => JSValue -> String -> Result a
 obj ! key = maybe (fail $ "CanonicalJSON.(!): Could not find key: " ++ show key)
             readJSON

src/compiler/GF/Grammar/Lexer.x

@@ -1,5 +1,6 @@
 -- -*- haskell -*-
 {
+{-# LANGUAGE CPP #-}
 module GF.Grammar.Lexer
          ( Token(..), Posn(..)
          , P, runP, runPartial, token, lexer, getPosn, failLoc
@@ -18,6 +19,7 @@ import qualified Data.Map as Map
 import Data.Word(Word8)
 import Data.Char(readLitChar)
 --import Debug.Trace(trace)
+import qualified Control.Monad.Fail as Fail
 }
 
 
@@ -282,8 +284,12 @@ instance Monad P where
   (P m) >>= k = P $ \ s -> case m s of
                              POk s a          -> unP (k a) s
                              PFailed posn err -> PFailed posn err
+
+
+instance Fail.MonadFail P where
   fail msg    = P $ \(_,AI posn _ _) -> PFailed posn msg
 
+
 runP :: P a -> BS.ByteString -> Either (Posn,String) a
 runP p bs = snd <$> runP' p (Pn 1 0,bs)
 

src/compiler/GF/Grammar/Macros.hs

@@ -32,6 +32,7 @@ import Control.Monad (liftM, liftM2, liftM3)
 import Data.List (sortBy,nub)
 import Data.Monoid
 import GF.Text.Pretty(render,(<+>),hsep,fsep)
+import qualified Control.Monad.Fail as Fail
 
 -- ** Functions for constructing and analysing source code terms.
 
@@ -237,7 +238,7 @@ isPredefConstant t = case t of
   Q (mod,_) | mod == cPredef || mod == cPredefAbs -> True
   _                                               -> False
 
-checkPredefError :: Monad m => Term -> m Term
+checkPredefError :: Fail.MonadFail m => Term -> m Term
 checkPredefError t =
     case t of
       Error s -> fail ("Error: "++s)

src/compiler/GF/Infra/CheckM.hs

@@ -32,6 +32,7 @@ import System.FilePath(makeRelative)
 import Control.Parallel.Strategies(parList,rseq,using)
 import Control.Monad(liftM,ap)
 import Control.Applicative(Applicative(..))
+import qualified Control.Monad.Fail as Fail
 
 type Message = Doc
 type Error   = Message
@@ -53,6 +54,9 @@ instance Monad Check where
                  (ws,Success x) -> unCheck (g x) {-ctxt-} ws
                  (ws,Fail msg)  -> (ws,Fail msg)
 
+instance Fail.MonadFail Check where
+  fail = raise
+
 instance Applicative Check where
   pure = return
   (<*>) = ap

src/compiler/GF/Infra/Option.hs

@@ -44,6 +44,7 @@ import Data.Set (Set)
 import qualified Data.Set as Set
 
 import PGF.Internal(Literal(..))
+import qualified Control.Monad.Fail as Fail
 
 usageHeader :: String
 usageHeader = unlines 
@@ -548,7 +549,7 @@ lookupShow xs z = fromMaybe "lookupShow" $ lookup z [(y,x) | (x,y) <- xs]
 lookupReadsPrec :: [(String,a)] -> Int -> ReadS a
 lookupReadsPrec xs _ s = [(z,rest) | (x,rest) <- lex s, (y,z) <- xs, y == x]
 
-onOff :: Monad m => (Bool -> m a) -> Bool -> ArgDescr (m a)
+onOff :: Fail.MonadFail m => (Bool -> m a) -> Bool -> ArgDescr (m a)
 onOff f def = OptArg g "[on,off]"
   where g ma = maybe (return def) readOnOff ma >>= f
         readOnOff x = case map toLower x of
@@ -556,7 +557,7 @@ onOff f def = OptArg g "[on,off]"
                         "off" -> return False
                         _     -> fail $ "Expected [on,off], got: " ++ show x
 
-readOutputFormat :: Monad m => String -> m OutputFormat
+readOutputFormat :: Fail.MonadFail m => String -> m OutputFormat
 readOutputFormat s = 
     maybe (fail $ "Unknown output format: " ++ show s) return $ lookup s outputFormats
 

src/compiler/GF/Infra/SIO.hs

@@ -42,6 +42,7 @@ import qualified GF.Command.Importing as GF(importGrammar, importSource)
 #ifdef C_RUNTIME
 import qualified PGF2
 #endif
+import qualified Control.Monad.Fail as Fail
 
 -- * The SIO monad
 
@@ -58,6 +59,9 @@ instance Monad SIO where
   return x = SIO (const (return x))
   SIO m1 >>= xm2 = SIO $ \ h -> m1 h >>= \ x -> unS (xm2 x) h
 
+instance Fail.MonadFail SIO where
+  fail = liftSIO . fail
+
 instance Output SIO where
   ePutStr = lift0 . ePutStr
   ePutStrLn = lift0 . ePutStrLn

src/compiler/GF/Infra/UseIO.hs

@@ -159,6 +159,9 @@ instance ErrorMonad IO where
                                 then h (ioeGetErrorString e)
                                 else ioError e
 {-
+-- Control.Monad.Fail import will become redundant in GHC 8.8+
+import qualified Control.Monad.Fail as Fail
+
 instance Functor IOE where fmap = liftM
 
 instance Applicative IOE where
@@ -170,7 +173,15 @@ instance  Monad IOE where
   IOE c >>= f = IOE $ do 
                   x <- c          -- Err a
                   appIOE $ err raise f x         -- f :: a -> IOE a
+
+ #if !(MIN_VERSION_base(4,13,0))
   fail = raise
+ #endif
+
+instance Fail.MonadFail IOE where
+  fail = raise
+
+
 -}
 
 -- | Print the error message and return a default value if the IO operation 'fail's

src/compiler/GF/Interactive.hs

@@ -38,6 +38,9 @@ import GF.Server(server)
 #endif
 
 import GF.Command.Messages(welcome)
+import GF.Infra.UseIO (Output)
+-- Provides an orphan instance of MonadFail for StateT in ghc versions < 8
+import Control.Monad.Trans.Instances ()
 
 -- | Run the GF Shell in quiet mode (@gf -run@).
 mainRunGFI :: Options -> [FilePath] -> IO ()
@@ -99,7 +102,7 @@ timeIt act =
 
 -- | Optionally show how much CPU time was used to run an IO action
 optionallyShowCPUTime :: (Monad m,MonadSIO m) => Options -> m a -> m a
-optionallyShowCPUTime opts act 
+optionallyShowCPUTime opts act
   | not (verbAtLeast opts Normal) = act
   | otherwise = do (dt,r) <- timeIt act
                    liftSIO $ putStrLnFlush $ show (dt `div` 1000000000) ++ " msec"
@@ -363,7 +366,7 @@ wordCompletion gfenv (left,right) = do
     pgf    = multigrammar gfenv
     cmdEnv = commandenv gfenv
     optLang opts = valCIdOpts "lang" (head (languages pgf)) opts
-    optType opts = 
+    optType opts =
       let str = valStrOpts "cat" (showCId $ lookStartCat pgf) opts
       in case readType str of
            Just ty -> ty
@@ -410,7 +413,7 @@ wc_type = cmd_name
     option x y (c  :cs)
       | isIdent c       = option x y cs
       | otherwise       = cmd x cs
-      
+
     optValue x y ('"':cs) = str x y cs
     optValue x y cs       = cmd x cs
 
@@ -428,7 +431,7 @@ wc_type = cmd_name
       where
         x1 = take (length x - length y - d) x
         x2 = takeWhile (\c -> isIdent c || isSpace c || c == '-' || c == '=' || c == '"') x1
-        
+
         cmd = case [x | (x,cs) <- RP.readP_to_S pCommand x2, all isSpace cs] of
 	        [x] -> Just x
                 _   -> Nothing

src/runtime/haskell-bind/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.2.1
+
+- Remove deprecated pgf_print_expr_tuple
+- Added an API for cloning expressions/types/literals
+
 ## 1.2.0
 
 - Stop `pgf-shell` from being built by default.

src/runtime/haskell-bind/HACKAGE.md

@@ -0,0 +1,10 @@
+# Instructions for uploading to Hackage
+
+You will need a Hackage account for steps 4 & 5.
+
+1. Bump the version number in `pgf2.cabal`
+2. Add details in `CHANGELOG.md`
+3. Run `stack sdist` (or `cabal sdist`)
+4. Visit `https://hackage.haskell.org/upload` and upload the file `./.stack-work/dist/x86_64-osx/Cabal-2.2.0.1/pgf2-x.y.z.tar.gz` (or Cabal equivalent)
+5. If successful, upload documentation with `./stack-haddock-upload.sh pgf2 x.y.z` (compilation on Hackage's servers will fail because of missing C libraries)
+6. Commit and push to this repository (`gf-core`)

src/runtime/haskell-bind/pgf2.cabal

@@ -1,5 +1,5 @@
 name: pgf2
-version: 1.2.0
+version: 1.2.1
 synopsis: Bindings to the C version of the PGF runtime
 description:
   GF, Grammatical Framework, is a programming language for multilingual grammar applications.

src/runtime/haskell/Data/Binary/Get.hs

@@ -101,6 +101,10 @@ import GHC.Word
 --import GHC.Int
 #endif
 
+-- Control.Monad.Fail import will become redundant in GHC 8.8+
+import qualified Control.Monad.Fail as Fail
+
+
 -- | The parse state
 data S = S {-# UNPACK #-} !B.ByteString  -- current chunk
            L.ByteString                  -- the rest of the input
@@ -126,6 +130,11 @@ instance Monad Get where
                              (a, s') -> unGet (k a) s')
     {-# INLINE (>>=) #-}
 
+#if !(MIN_VERSION_base(4,13,0))
+    fail      = failDesc
+#endif
+
+instance Fail.MonadFail Get where
     fail      = failDesc
 
 instance MonadFix Get where

src/server/CGI.hs

@@ -4,7 +4,7 @@ import Network.CGI as C(
        CGI,ContentType(..),Accept(..),Language(..),
        getVarWithDefault,readInput,negotiate,requestAcceptLanguage,getInput,
        setHeader,output,outputFPS,outputError,
-       handleErrors,catchCGI,throwCGI,
+       handleErrors,
        liftIO)
 import Network.CGI.Protocol as C(CGIResult(..),CGIRequest(..),Input(..),
                                  Headers,HeaderName(..))

src/server/CGIUtils.hs

@@ -15,11 +15,14 @@ import System.Posix
 #endif
 
 import CGI(CGI,CGIResult,setHeader,output,outputFPS,outputError,
-           getInput,catchCGI,throwCGI)
+           getInput)
 
 import Text.JSON
 import qualified Codec.Binary.UTF8.String as UTF8 (encodeString)
 import qualified Data.ByteString.Lazy as BS
+import Control.Monad.Catch (MonadThrow(throwM))
+import Network.CGI.Monad (catchCGI)
+import Control.Monad.Catch (MonadCatch(catch))
 
 -- * Logging
 
@@ -53,11 +56,11 @@ instance Exception CGIError where
   fromException (SomeException e) = cast e
 
 throwCGIError :: Int -> String -> [String] -> CGI a
-throwCGIError c m t = throwCGI $ toException $ CGIError c m t
+throwCGIError c m t = throwM $ toException $ CGIError c m t
 
 handleCGIErrors :: CGI CGIResult -> CGI CGIResult
 handleCGIErrors x =
-    x `catchCGI` \e -> case fromException e of
+    x `catch` \e -> case fromException e of
                          Nothing -> throw e
                          Just (CGIError c m t) -> do setXO; outputError c m t
 

src/tools/c/GFCC/ErrM.hs

@@ -4,6 +4,10 @@
 -- This file comes with NO WARRANTY and may be used FOR ANY PURPOSE.
 module GFCC.ErrM where
 
+-- Control.Monad.Fail import will become redundant in GHC 8.8+
+import qualified Control.Monad.Fail as Fail
+
+
 -- the Error monad: like Maybe type with error msgs
 
 data Err a = Ok a | Bad String
@@ -11,6 +15,13 @@ data Err a = Ok a | Bad String
 
 instance Monad Err where
   return      = Ok
-  fail        = Bad
   Ok a  >>= f = f a
   Bad s >>= f = Bad s
+
+#if !(MIN_VERSION_base(4,13,0))
+  fail        = Bad
+#endif
+
+instance Fail.MonadFail Err where
+  fail        = Bad
+