Fix ambiguous syntax parsing

CHANGELOG

@@ -1,6 +1,6 @@
 # 1.42.6 (2020-XX-XX)
 
- * n/a
+ * Fix ambiguous syntax parsing
 
 # 1.42.5 (2020-02-11)
 

src/Lexer.php

@@ -500,10 +500,14 @@ class Lexer implements \Twig_LexerInterface
         foreach ($operators as $operator => $length) {
             // an operator that ends with a character must be followed by
             // a whitespace or a parenthesis
+            $r = preg_quote($operator, '/');
             if (ctype_alpha($operator[$length - 1])) {
-                $r = preg_quote($operator, '/').'(?=[\s()])';
-            } else {
-                $r = preg_quote($operator, '/');
+                $r .= '(?=[\s()])';
+            }
+
+            // an operator that begins with a character must have a space before
+            if (ctype_alpha($operator[0])) {
+                $r = '(?<=\s)'.$r;
             }
 
             // an operator with a space can be any amount of whitespaces

tests/Fixtures/tests/in.test

@@ -57,8 +57,13 @@ Twig supports the in operator
 
 {{ safe in ['foo', 'bar'] ? 'OK' : 'KO' }}
 {{ 'fo' in safe ? 'OK' : 'KO' }}
+
+{{ foo.not in ['not'] ? 'OK' : 'KO' }}
+{{ 'value'|not in ['not value'] ? 'OK' : 'KO' }}
+{{ foo.not not in ['not'] ? 'KO' : 'OK' }}
+{{ 'value'|not not in ['not value'] ? 'KO' : 'OK' }}
 --DATA--
-return ['bar' => 'bar', 'foo' => ['bar' => 'bar'], 'dir_object' => new \SplFileInfo(dirname(__FILE__)), 'object' => new \stdClass(), 'resource' => opendir(dirname(__FILE__)), 'safe' => new \Twig\Markup('foo', 'UTF-8')]
+return ['bar' => 'bar', 'foo' => ['bar' => 'bar', 'not' => 'not'], 'dir_object' => new \SplFileInfo(dirname(__FILE__)), 'object' => new \stdClass(), 'resource' => opendir(dirname(__FILE__)), 'safe' => new \Twig\Markup('foo', 'UTF-8')]
 --EXPECT--
 OK
 OK
@@ -116,3 +121,8 @@ OK
 
 OK
 OK
+
+OK
+OK
+OK
+OK

tests/IntegrationTest.php

@@ -164,6 +164,7 @@ class TwigTestExtension extends AbstractExtension
             new TwigFilter('magic_call_array', ['Twig\Tests\TwigTestExtension', 'magicStaticCall']),
             new TwigFilter('*_path', [$this, 'dynamic_path']),
             new TwigFilter('*_foo_*_bar', [$this, 'dynamic_foo']),
+            new TwigFilter('not', [$this, 'notFilter']),
         ];
     }
 
@@ -188,6 +189,11 @@ class TwigTestExtension extends AbstractExtension
         ];
     }
 
+    public function notFilter($value)
+    {
+        return 'not '.$value;
+    }
+
     public function §Filter($value)
     {
         return "§{$value}§";