From 32b78b8ee5c9e26af85b6119d083035e1af9c1b7 Mon Sep 17 00:00:00 2001
From: Erez Shinan <erezshin+git@gmail.com>
Date: Mon, 30 Jul 2018 17:54:12 +0300
Subject: [PATCH] BUGFIX: Repeated use of optional rules tripped up the
 simplifier, manifesting when aliases were used (Issue #197)

---
 lark/load_grammar.py | 1 +
 tests/test_parser.py | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 6da2df0..8f924c5 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -235,6 +235,7 @@ class SimplifyRule_Visitor(Visitor):
                 tree.children = [self.visit(ST('expansion', [option if i==j else other
                                                             for j, other in enumerate(tree.children)]))
                                     for option in set(child.children)]
+                self._flatten(tree)
                 break
 
     def alias(self, tree):
diff --git a/tests/test_parser.py b/tests/test_parser.py
index c4d7147..a029abe 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -148,6 +148,9 @@ class TestParsers(unittest.TestCase):
         self.assertEqual( r.children, ["<c>"] )
 
 
+    def test_alias(self):
+        Lark("""start: ["a"] "b" ["c"] "e" ["f"] ["g"] ["h"] "x" -> d """)
+
 
 
 def _make_full_earley_test(LEXER):