Use decorator without making type hinting mad

MailingListBaseDecorator.php

<?php

namespace App;

use App\Contracts\MailingListService;

abstract class MailingListBaseDecorator implements MailingListService
{
    protected $mailingList;

    public function __construct(MailingListService $mailingList = null) {
        $this->mailingList = $mailingList;
    }
    public function addEmailToList(string $list, string $email, string $firstName = '', string $lastName = '') {
        error_log ('base addEmailToList');
        $this->__call(__FUNCTION__, func_get_args());
    }
    public function sendMarketingEmail(string $email, string $firstname, string $lastname = ''){
        error_log ('base sendMarketingEmail');
        $this->__call(__FUNCTION__, func_get_args());
    }
    public function __call($method, $args) {
        return $this->mailingList->{$method}(...$args);
    }
}

MailingListService.php

<?php namespace App\Contracts;

interface MailingListService
{
    public function addEmailToList(string $list, string $email, string $firstName = '', string $lastName = '');
    public function sendMarketingEmail(string $email, string $firstname, string $lastname = '');
} // interface MailingListService

TestInheriterA.php

<?php

namespace App;

use App\MailingListBaseDecorator;
use App\Contracts\MailingListService;

class TestInheriterA extends MailingListBaseDecorator
{
    public function decoratedFunctionA() {
        error_log ('decorated functionA');
    }
    public function addEmailToList(string $list, string $email, string $firstName = '', string $lastName = '') {
        error_log ('overwritten addEmailToList A');
    }
}

TestInheriterB

<?php

namespace App;

use App\MailingListBaseDecorator;
use App\Contracts\MailingListService;

class TestInheriterB extends MailingListBaseDecorator
{
    public function decoratedFunctionB() {
        error_log ('decorated function B');
    }
    public function addEmailToList(string $list, string $email, string $firstName = '', string $lastName = '') {
        error_log ('overwritten addEmailToList B');
    }
}

tinker_output.txt

>>> $c = new App\TestInheriterA(new App\TestInheriterB)
=> App\TestInheriterA {#1147}
>>> $c->decoratedFunctionA()
decorated functionA
=> null
>>> $c->decoratedFunctionB()
decorated function B
=> null
>>> $c->addEmailToList('list','email')
overwritten addEmailToList A
=> null
>>> 
>>> class_implements($c)
=> [
     "App\Contracts\MailingListService" => "App\Contracts\MailingListService",
   ]