Better error for literal with bad escaping (Issue #287)

erezsh · erezsh · commit f06a83a8a79e · 2019-08-28T23:50:36.000+02:00
diff --git a/lark/load_grammar.py b/lark/load_grammar.py
@@ -351,7 +351,10 @@ def _fix_escaping(s):
     for n in i:
         w += n
         if n == '\\':
-            n2 = next(i)
+            try:
+                n2 = next(i)
+            except StopIteration:
+                raise ValueError("Literal ended unexpectedly (bad escaping): `%r`" % s)
             if n2 == '\\':
                 w += '\\\\'
             elif n2 not in 'uxnftr':
