From 5c02166c3f6c687419db94c8d754068c783f523b Mon Sep 17 00:00:00 2001
From: Erez Shinan <erezshin+git@gmail.com>
Date: Thu, 14 Sep 2017 01:04:34 +0300
Subject: [PATCH] Bugfix #25: Ambiguity resolver sometimes failed under Python3

---
 lark/parsers/resolve_ambig.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lark/parsers/resolve_ambig.py b/lark/parsers/resolve_ambig.py
index ca0d0f6..f1a4431 100644
--- a/lark/parsers/resolve_ambig.py
+++ b/lark/parsers/resolve_ambig.py
@@ -24,7 +24,10 @@ def _compare_rules(rule1, rule2):
 
 def _compare_drv(tree1, tree2):
     if not (isinstance(tree1, Tree) and isinstance(tree2, Tree)):
-        return -compare(tree1, tree2)
+        try:
+            return -compare(tree1, tree2)
+        except TypeError:
+            return 0
 
     try:
         rule1, rule2 = tree1.rule, tree2.rule