private function traverseVariable(\PHPParser_Node_Expr_Variable $node, LinkedFlowScope $scope)
 {
     if ('this' === $node->name) {
         if (null === $scope->getTypeOfThis()) {
             $node->setAttribute('type', $this->typeRegistry->getNativeType('none'));
             return $scope;
         }
         $node->setAttribute('type', $this->typeRegistry->getThisType($scope->getTypeOfThis()));
         return $scope;
     }
     if (is_string($node->name)) {
         $slot = $scope->getSlot($node->name);
         if ($slot && ($type = $slot->getType())) {
             $node->setAttribute('type', $type);
         }
     } else {
         $scope = $this->traverseChildren($node, $scope);
     }
     return $scope;
 }