WooCommerce coupon usage restriction by allowed user roles

plugged.php

<?php /* No copiar esta linea */

// Add new field - Coupon usage restriction tab
function archtkt_woocommerce_coupon_options_usage_restriction( $coupon_get_id, $coupon ) {
    woocommerce_wp_text_input( array( 
        'id' => 'customer_user_role',  
        'label' => __( 'User role restrictions', 'woocommerce' ),  
        'placeholder' => __( 'No restrictions', 'woocommerce' ),  
        'description' => __( 'List of allowed user roles. Separate user roles with commas.', 'woocommerce' ),  
        'desc_tip' => true,  
        'type' => 'text',  
    )); 
}
add_action( 'woocommerce_coupon_options_usage_restriction', 'archtkt_woocommerce_coupon_options_usage_restriction', 10, 2 );

// Save role as coupon usage restriction
function archtkt_woocommerce_coupon_options_save( $post_id, $coupon ) {
    update_post_meta( $post_id, 'customer_user_role', $_POST['customer_user_role'] );
}
add_action( 'woocommerce_coupon_options_save', 'archtkt_woocommerce_coupon_options_save', 10, 2 );

// Validate user role at coupon usage
function archtkt_filter_woocommerce_coupon_is_valid( $is_valid, $coupon, $discount ) {
    // Get meta
    $customer_user_role = $coupon->get_meta('customer_user_role');

    // NOT empty
    if( ! empty( $customer_user_role ) ) {
        // Convert string to array
        $customer_user_role = explode(', ', $customer_user_role);

        // Get current user role
        $user = wp_get_current_user();
        $roles = ( array ) $user->roles;

        // Start with not valid coupon
        $is_valid = false;

        if( ! empty( $roles ) ) {
          foreach ($roles as $role) {

            // Compare
            $compare = in_array( $role, $customer_user_role );

            if ( $compare ) {
                $is_valid = true;
            }
          }
        }
    }

    return $is_valid;
}
add_filter( 'woocommerce_coupon_is_valid', 'archtkt_filter_woocommerce_coupon_is_valid', 10, 3 );

Thanks for your code. It's great and useful.
If I want to take a noice, this coupon is for only role. how can do it?
$is_valid = false . ' this coupon is for only role.'; < that's ok?