GF source lexer: allow numeric character escapes in string literals

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"...

1 files 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.