WooCommerce Coupons Fix: email restrictions

functions.php

/*
  WooCommerce email restriction for coupons does not work. This fix corrects it. 
  Include this code snippet in your theme or plugin.
*/

add_filter( 'woocommerce_coupon_is_valid', 'wc_riotxoa_coupon_is_valid', 10, 2 );

if ( ! function_exists( 'wc_riotxoa_coupon_is_valid' ) ) {

	function wc_riotxoa_coupon_is_valid( $result, $coupon ) {
		$user = wp_get_current_user();

		$restricted_emails = $coupon->get_email_restrictions();

		return ( in_array( $user->user_email, $restricted_emails ) ? $result : false );
	}
}

In addiction to the discussion, if needed to verify wildcard restrictions. Example *@gmail.com.

It is possible to use a function of WC_Cart: is_coupon_emails_allowed:

add_filter('woocommerce_coupon_is_valid', function ($result, $coupon) {
    if (null === WC()->cart) {
        return $result;
    }

    $user = wp_get_current_user();
    $restricted_emails = $coupon->get_email_restrictions();

    if (count($restricted_emails) > 0) {
        return WC()->cart->is_coupon_emails_allowed(
            [$user->user_email],
            $restricted_emails
        );
    } else {
        return $result;
    }
}, 10, 2);

Thank you @saulopaiva!