Description:
------------
The return type hinting is not working as expected, in this case I want to return a "resource" (such as the ones returned by curl functions, mysql functions, etc) but PHP thinks I must return an instance of an (non-existant) "resource" class, which breaks the purpose of the return type hinting in this function, the documentation on this lacks some specific information for some php types (like mixed, object and resource), so I may be making a mistake here (and probably too much assumptions).

Test script:
---------------
<?php
declare(strict_types=1);
function prepareCURLResource(string $url) : resource
{
    $curl = curl_init($url);

    curl_setopt($curl, CURLOPT_COOKIEFILE, "/tmp");
    curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 3);

    return $curl;
}

$res = prepareCURLResource("http://localhost");

echo htmlentities(curl_exec($curl));

Expected result:
----------------
The source code of the given URL (http://localhost) in this case.

Actual result:
--------------
[Wed Feb 03 22:46:42 2016] [warn] [client 192.168.100.2] mod_fcgid: stderr: PHP Fatal error:  Uncaught TypeError: Return value of prepareCURLResource() must be an instance of resource, resource returned in /var/www/test.php:12
[Wed Feb 03 22:46:42 2016] [warn] [client 192.168.100.2] mod_fcgid: stderr: Stack trace:
[Wed Feb 03 22:46:42 2016] [warn] [client 192.168.100.2] mod_fcgid: stderr: #0 /var/www/test.php(15): prepareCURLResource('http://localhost')
[Wed Feb 03 22:46:42 2016] [warn] [client 192.168.100.2] mod_fcgid: stderr: #1 {main}
[Wed Feb 03 22:46:42 2016] [warn] [client 192.168.100.2] mod_fcgid: stderr:   thrown in /var/www/test.php on line 12