From 5663351a49f5ad49778dd9a4cbf30a6d7b29f429 Mon Sep 17 00:00:00 2001
From: Fabien Potencier <fabien@potencier.org>
Date: Sun, 23 Feb 2020 09:40:57 +0100
Subject: [PATCH] Fix ambiguous syntax parsing

---
 src/Lexer.php                       |  3 ++-
 tests/Fixtures/expressions/not.test | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 tests/Fixtures/expressions/not.test

diff --git a/src/Lexer.php b/src/Lexer.php
index 2de5fc79a..b93790c61 100644
--- a/src/Lexer.php
+++ b/src/Lexer.php
@@ -506,8 +506,9 @@ class Lexer implements \Twig_LexerInterface
             }
 
             // an operator that begins with a character must have a space before
+            // or a parenthesis
             if (ctype_alpha($operator[0])) {
-                $r = '(?<=\s)'.$r;
+                $r = '(?<=[\s(])'.$r;
             }
 
             // an operator with a space can be any amount of whitespaces
diff --git a/tests/Fixtures/expressions/not.test b/tests/Fixtures/expressions/not.test
new file mode 100644
index 000000000..40914a3e1
--- /dev/null
+++ b/tests/Fixtures/expressions/not.test
@@ -0,0 +1,10 @@
+--TEST--
+not
+--TEMPLATE--
+{{ (not false) ? 'OK' : 'KO' }}
+{{ not false ? 'OK' : 'KO' }}
+--DATA--
+return []
+--EXPECT--
+OK
+OK