From 1ccdd0d9fdea3a4f457101ba205c37f28abb8e70 Mon Sep 17 00:00:00 2001
From: hallgren <hallgren@chalmers.se>
Date: Tue, 29 Sep 2015 12:18:35 +0000
Subject: [PATCH] GF source lexer: allow numeric character escapes in string
 literals
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This makes the output from PGF.showExpr (and other Haskell code that uses
the Prelude.show function to show strings) parsable as GF source code in
more cases.

This is a workaround for the problem that GHC's implementation of the show
function uses numeric escapes for printable non-ASCII characters, e.g.
show "dålig" = "d\229lig"...
---
 src/compiler/GF/Grammar/Lexer.x | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/compiler/GF/Grammar/Lexer.x b/src/compiler/GF/Grammar/Lexer.x
index c2cbb4c47..f073bcdfc 100644
--- a/src/compiler/GF/Grammar/Lexer.x
+++ b/src/compiler/GF/Grammar/Lexer.x
@@ -16,6 +16,7 @@ import qualified Data.ByteString.Internal as BS(w2c)
 import qualified Data.ByteString.UTF8 as UTF8
 import qualified Data.Map as Map
 import Data.Word(Word8)
+import Data.Char(readLitChar)
 --import Debug.Trace(trace)
 }
 
@@ -39,7 +40,7 @@ $white+ ;
 \' ([. # [\' \\ \n]] | (\\ (\' | \\)))+ \' { tok (T_Ident . identS . unescapeInitTail . unpack) }
 (\_ | $l)($l | $d | \_ | \')*   { tok ident }
 
-\" ([$u # [\" \\ \n]] | (\\ (\" | \\ | \' | n | t)))* \" { tok (T_String . unescapeInitTail . unpack) }
+\" ([$u # [\" \\ \n]] | (\\ (\" | \\ | \' | n | t | $d+)))* \" { tok (T_String . unescapeInitTail . unpack) }
 
 (\-)? $d+                       { tok (T_Integer . read . unpack) }
 (\-)? $d+ \. $d+ (e (\-)? $d+)? { tok (T_Double  . read . unpack) }
@@ -217,13 +218,11 @@ resWords = Map.fromList
 unescapeInitTail :: String -> String
 unescapeInitTail = unesc . tail where
   unesc s = case s of
-    '\\':c:cs | elem c ['\"', '\\', '\''] -> c : unesc cs
-    '\\':'n':cs  -> '\n' : unesc cs
-    '\\':'t':cs  -> '\t' : unesc cs
+    []         -> []
     '\"':[]    -> []
     '\'':[]    -> []
-    c:cs      -> c : unesc cs
-    _         -> []
+    _          -> case readLitChar s of
+                    [(c,cs)] -> c:unesc cs
 
 -------------------------------------------------------------------
 -- Alex wrapper code.