Source

File: wp-includes/template.php

function get_archive_template() {
	$post_types = array_filter( (array) get_query_var( 'post_type' ) );

	$templates = array();

	if ( count( $post_types ) == 1 ) {
		$post_type   = reset( $post_types );
		$templates[] = "archive-{$post_type}.php";
	}
	$templates[] = 'archive.php';

	return get_query_template( 'archive', $templates );
}