From f2e4b89a22a1c7c7304e3a712e47e6d9f3f763e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20K=C3=A4llberg?= <anka.213@gmail.com>
Date: Thu, 8 Oct 2020 17:41:44 +0200
Subject: [PATCH] Fix syntax error problem for older versions of GHC

---
 src/compiler/GF/Grammar/Lexer.x | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/compiler/GF/Grammar/Lexer.x b/src/compiler/GF/Grammar/Lexer.x
index fe455c58a..bde0aa064 100644
--- a/src/compiler/GF/Grammar/Lexer.x
+++ b/src/compiler/GF/Grammar/Lexer.x
@@ -35,7 +35,7 @@ $u = [.\n]                -- universal: any character
 
 :-
 "--" [.]* ; -- Toss single line comments
-"{-" ([$u # \-] | \- [$u # \}])* ("-")+ "}" ; 
+"{-" ([$u # \-] | \- [$u # \}])* ("-")+ "}" ;
 
 $white+ ;
 @rsyms                          { tok ident }
@@ -138,7 +138,7 @@ data Token
 
 res = eitherResIdent
 eitherResIdent :: (Ident -> Token) -> Ident -> Token
-eitherResIdent tv s = 
+eitherResIdent tv s =
   case Map.lookup s resWords of
     Just t  -> t
     Nothing -> tv s
@@ -285,6 +285,10 @@ instance Monad P where
                              POk s a          -> unP (k a) s
                              PFailed posn err -> PFailed posn err
 
+#if !(MIN_VERSION_base(4,13,0))
+  -- Monad(fail) will be removed in GHC 8.8+
+  fail = Fail.fail
+#endif
 
 instance Fail.MonadFail P where
   fail msg    = P $ \(_,AI posn _ _) -> PFailed posn msg