找出destination() 在Order对象存在时仍可能产生警告的原因。
php
<?php
final class Address
{
public function __construct(public string $city) {}
}
final class Customer
{
public function __construct(public ?Address $address = null) {}
}
final class Order
{
public function __construct(public ?Customer $customer = null) {}
}
function destination(?Order $order): string
{
return $order?->customer->address?->city ?? 'pickup';
}