LanguageSelect.php

<?php

namespace Drupal\Core\Render\Element;

use Drupal\Core\Language\LanguageInterface;
use Drupal\Core\Render\Attribute\FormElement;

/**
 * Provides a form element for selecting a language.
 *
 * This does not render an actual form element, but always returns the value of
 * the default language. It is then extended by Language module via
 * language_element_info_alter() to provide a proper language selector.
 *
 * @see language_element_info_alter()
 */
class LanguageSelect extends FormElementBase {
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() {
        return [
            '#input' => TRUE,
            '#default_value' => LanguageInterface::LANGCODE_NOT_SPECIFIED,
        ];
    }

}