From 251845f83ea52965b5205fd231ffa2c87bb34de6 Mon Sep 17 00:00:00 2001
From: Andreas Källberg <anka.213@gmail.com>
Date: Wed, 5 Aug 2020 16:20:35 +0200
Subject: First attempt at fixing incompabilities with newer cabal

---
 src/compiler/GF/Grammar/Lexer.x | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'src/compiler/GF/Grammar')

diff --git a/src/compiler/GF/Grammar/Lexer.x b/src/compiler/GF/Grammar/Lexer.x
index d1550dd09..c19a32e3b 100644
--- a/src/compiler/GF/Grammar/Lexer.x
+++ b/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 +19,9 @@ import qualified Data.Map as Map
 import Data.Word(Word8)
 import Data.Char(readLitChar)
 --import Debug.Trace(trace)
+
+-- Control.Monad.Fail import will become redundant in GHC 8.8+
+import qualified Control.Monad.Fail as Fail
 }
 
 
@@ -282,8 +286,17 @@ 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
+
+#if !(MIN_VERSION_base(4,13,0))
+  fail msg    = P $ \(_,AI posn _ _) -> PFailed posn msg
+#endif
+
+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)
 
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