fixed class usage

lib/Twig/Environment.php

@@ -116,7 +116,7 @@ class Twig_Environment
         $options = array_merge([
             'debug' => false,
             'charset' => 'UTF-8',
-            'base_template_class' => '\\'.Twig\Template::class,
+            'base_template_class' => Template::class,
             'strict_variables' => false,
             'autoescape' => 'html',
             'cache' => false,
@@ -126,8 +126,8 @@ class Twig_Environment
 
         $this->debug = (bool) $options['debug'];
         $this->setCharset($options['charset']);
-        $this->baseTemplateClass = $options['base_template_class'];
-        if ('\Twig\Template' !== $options['base_template_class']) {
+        $this->baseTemplateClass = '\\'.ltrim($options['base_template_class'], '\\');
+        if ('\Twig\Template' !== $this->baseTemplateClass && '\Twig_Template' !== $this->baseTemplateClass) {
             @trigger_error('The "base_template_class" option on '.__CLASS__.' is deprecated since Twig 2.7.0.', E_USER_DEPRECATED);
         }
         $this->autoReload = null === $options['auto_reload'] ? $this->debug : (bool) $options['auto_reload'];

lib/Twig/Error.php

@@ -65,7 +65,7 @@ class Twig_Error extends \Exception
 
         if (null === $source) {
             $name = null;
-        } elseif (!$source instanceof Source) {
+        } elseif (!$source instanceof Source && !$source instanceof \Twig_Source) {
             @trigger_error(sprintf('Passing a string as a source to %s is deprecated since Twig 2.6.1; pass a Twig\Source instance instead.', __CLASS__), E_USER_DEPRECATED);
             $name = $source;
         } else {

lib/Twig/Extension/Escaper.php

@@ -10,6 +10,7 @@
  */
 
 use Twig\Extension\AbstractExtension;
+use Twig\FileExtensionEscapingStrategy;
 use Twig\NodeVisitor\EscaperNodeVisitor;
 use Twig\TokenParser\AutoEscapeTokenParser;
 use Twig\TwigFilter;
@@ -56,7 +57,7 @@ final class Twig_Extension_Escaper extends AbstractExtension
     public function setDefaultStrategy($defaultStrategy)
     {
         if ('name' === $defaultStrategy) {
-            $defaultStrategy = ['Twig_FileExtensionEscapingStrategy', 'guess'];
+            $defaultStrategy = [FileExtensionEscapingStrategy::class, 'guess'];
         }
 
         $this->defaultStrategy = $defaultStrategy;

lib/Twig/Parser.php

@@ -372,7 +372,7 @@ class Twig_Parser
         // "block" tags that are not captured (see above) are only used for defining
         // the content of the block. In such a case, nesting it does not work as
         // expected as the definition is not part of the default template code flow.
-        if ($nested && $node instanceof BlockReferenceNode) {
+        if ($nested && ($node instanceof BlockReferenceNode || $node instanceof \Twig_Node_BlockReference)) {
             //throw new SyntaxError('A block definition cannot be nested under non-capturing nodes.', $node->getTemplateLine(), $this->stream->getSourceContext());
             @trigger_error(sprintf('Nesting a block definition under a non-capturing node in "%s" at line %d is deprecated since Twig 2.5.0 and will become a syntax error in 3.0.', $this->stream->getSourceContext()->getName(), $node->getTemplateLine()), E_USER_DEPRECATED);
 
@@ -386,7 +386,7 @@ class Twig_Parser
 
         // here, $nested means "being at the root level of a child template"
         // we need to discard the wrapping "Twig_Node" for the "body" node
-        $nested = $nested || 'Twig_Node' !== \get_class($node);
+        $nested = $nested || ('Twig_Node' !== \get_class($node) && Node::class !== \get_class($node));
         foreach ($node as $k => $n) {
             if (null !== $n && null === $this->filterBodyNodes($n, $nested)) {
                 $node->removeNode($k);