Magento model extension experiment, return: "class does not exist"

Question

trying to create a new model class to be used as a source model for the admin configuration setting of a new module, I got the following message:

Class Makke\GroupOrders\Model\Config\Source\Sort does not exist
#0 C:\Projects\Marketplace\wamp\www\magento\vendor\magento\framework\Code\Reader\ClassReader.php(19): ReflectionClass->__construct('Makke\GroupOrde...')
#1 C:\Projects\Marketplace\wamp\www\magento\vendor\magento\framework\ObjectManager\Definition\Runtime.php(44): Magento\Framework\Code\Reader\ClassReader->getConstructor('Makke\GroupOrde...')
#2 C:\Projects\Marketplace\wamp\www\magento\vendor\magento\framework\ObjectManager\Factory\Dynamic\Developer.php(71): Magento\Framework\ObjectManager\Definition\Runtime->getParameters('Makke\GroupOrde...')

Could you please help me in understanding what's wrong considering the following files?

in my ..\wamp\www\magento\app\code\makke\module-group-orders\etc\adminhtml\system.xml there is the following field:

<field id="sort_mode" translate="label" type="select" sortOrder="20" showInDefault="1" showInWebsite="1" showInStore="0">
    <label>Sort by</label>
    <source_model>Makke\GroupOrders\Model\Config\Source\Sort</source_model>
</field>

and my ..\wamp\www\magento\app\code\makke\module-group-orders\Model\Config\Source\Sort.php is as follow:

/**
 * Used in creating options for Sort config value selection
 */
namespace Makke\GroupOrders\Model\Config\Source;

class Sort implements \Magento\Framework\Option\ArrayInterface
{
    /**
    * Options getter
    *
    * @return array
    */
    public function toOptionArray()
    {
        return [['value' => 'asc_by_km', 'label' => __('ASC by km')], 
        ['value' => 'desc_by_km', 'label' => __('DESC by km')], 
        ['value' => 'asc_by_popularity', 'label' => __('ASC by popularity')], 
        ['value' => 'desc_by_popularity', 'label' => __('DESC by popularity')]];
    }
    /**
    * Get options in "key-value" format
    *
    * @return array
    */
    public function toArray()
    {
        return ['asc_by_km' => __('ASC by km'), 
        'desc_by_km' => __('DESC by km'), 
        'asc_by_popularity' => __('ASC by popularity'), 
        'desc_by_popularity' => __('DESC by popularity')];
    }
}

Answer 1

Please try to change your file name (Sort.php) to other name, Sort is a php keyword name then you cannot use this name for a class name

Answer 2

You should rename app\code\makke\module-group-orders folder to app\code\Makke\GroupOrders