Description:
------------
If an interface that extends two other interfaces, the order of those two other interfaces should not matter. 

I found this bug when I was testing solutions for PSR18 and HTTPlug. Here is an 3v4l.org: https://3v4l.org/MMCL3

This bug might be related to https://bugs.php.net/bug.php?id=63816

Test script:
---------------
<?php

declare(strict_types=1);

interface Response {}

interface Request {}

class RespImpl implements Response {}

class ReqImpl implements Request {}

interface Psr {
    public function sendRequest(Request $request): Response;
}

interface Httplug {
    public function sendRequest(Request $request);
}

//interface PsrBridge extends Psr, Httplug {} // does work
interface PsrBridge extends Httplug, Psr {} // does not work

class HttpClient implements PsrBridge {
    public function sendRequest(Request $request): Response {
        return new RespImpl();
    }
}

$client = new HttpClient();
$response = $client->sendRequest(new ReqImpl());
echo $response instanceof Response ? 'OK' : 'Fail!';

Expected result:
----------------
I expect these two lines would give the same result: 

interface PsrBridge extends Psr, Httplug {}
interface PsrBridge extends Httplug, Psr {}

Actual result:
--------------
Fatal error: Declaration of Httplug::sendRequest(Request $request) must be compatible with Psr::sendRequest(Request $request): Response in /in/MMCL3 on line 22
Process exited with code 255.