Source

File: wp-includes/class-wp-widget.php

public function __construct( $id_base, $name, $widget_options = array(), $control_options = array() ) {
		$this->id_base         = empty( $id_base ) ? preg_replace( '/(wp_)?widget_/', '', strtolower( get_class( $this ) ) ) : strtolower( $id_base );
		$this->name            = $name;
		$this->option_name     = 'widget_' . $this->id_base;
		$this->widget_options  = wp_parse_args(
			$widget_options,
			array(
				'classname'                   => $this->option_name,
				'customize_selective_refresh' => false,
			)
		);
		$this->control_options = wp_parse_args( $control_options, array( 'id_base' => $this->id_base ) );
	}