MonadFail: Make backwards-compatible

src/compiler/GF/Grammar/Lexer.x

@@ -19,6 +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
 }
 
 
@@ -285,7 +286,7 @@ instance Monad P where
                              PFailed posn err -> PFailed posn err
 
 
-instance MonadFail P where
+instance Fail.MonadFail P where
   fail msg    = P $ \(_,AI posn _ _) -> PFailed posn msg
 
 

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 :: MonadFail m => Term -> m Term
+checkPredefError :: Fail.MonadFail m => Term -> m Term
 checkPredefError t =
     case t of
       Error s -> fail ("Error: "++s)