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

1 files changed, 12 insertions, 1 deletions

diff --git a/src/compiler/GF/Data/ErrM.hs b/src/compiler/GF/Data/ErrM.hs
index 033c1efac..288c61919 100644
--- a/src/compiler/GF/Data/ErrM.hs
+++ b/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)