fixed regression in string parsing (closes #580)

lib/Twig/ExpressionParser.php

@@ -170,23 +170,25 @@ class Twig_ExpressionParser
         $stream = $this->parser->getStream();
 
         $nodes = array();
-
+        // a string cannot be followed by another string in a single expression
+        $nextCanBeString = true;
         while (true) {
-            if ($stream->test(Twig_Token::STRING_TYPE)) {
+            if ($stream->test(Twig_Token::STRING_TYPE) && $nextCanBeString) {
                 $token = $stream->next();
                 $nodes[] = new Twig_Node_Expression_Constant($token->getValue(), $token->getLine());
-            } else if ($stream->test(Twig_Token::INTERPOLATION_START_TYPE)) {
+                $nextCanBeString = false;
+            } elseif ($stream->test(Twig_Token::INTERPOLATION_START_TYPE)) {
                 $stream->next();
                 $nodes[] = $this->parseExpression();
                 $stream->expect(Twig_Token::INTERPOLATION_END_TYPE);
+                $nextCanBeString = true;
             } else {
                 break;
             }
         }
 
         $expr = array_shift($nodes);
-
-        foreach($nodes as $node) {
+        foreach ($nodes as $node) {
             $expr = new Twig_Node_Expression_Binary_Concat($expr, $node, $node->getLine());
         }
 

test/Twig/Tests/ExpressionParserTest.php

@@ -144,6 +144,18 @@ class Twig_Tests_ExpressionParserTest extends PHPUnit_Framework_TestCase
         );
     }
 
+    /**
+     * @expectedException Twig_Error_Syntax
+     */
+    public function testStringExpressionDoesNotConcatenateTwoConsecutiveStrings()
+    {
+        $env = new Twig_Environment(new Twig_Loader_String(), array('cache' => false, 'autoescape' => false, 'optimizations' => 0));
+        $stream = $env->tokenize('{{ "a" "b" }}', 'index');
+        $parser = new Twig_Parser($env);
+
+        $parser->parse($stream);
+    }
+
     /**
      * @dataProvider getTestsForString
      */

test/Twig/Tests/Fixtures/expressions/strings.test

@@ -2,7 +2,9 @@
 Twig supports string interpolation
 --TEMPLATE--
 {{ "foo #{"foo #{bar} baz"} baz" }}
+{{ "foo #{bar}#{bar} baz" }}
 --DATA--
 return array('bar' => 'BAR');
 --EXPECT--
 foo foo BAR baz baz
+foo BARBAR baz