Description:
------------
We now have contravariance and covariance. With covariance, we can substitute a return type of `object` with a more specific type like `MyCustomClass` for example.

We cannot substitute `object` with `MyCustomClass` as a function argument typehint though.

I feel this is a bug. Why would it be allowed as a return type but not a typehint?

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

class MyClass
{}


// ----------


interface TestCo
{
    public function testCo(): object;
}

class TestCoImplementation implements TestCo
{
    public function testCo(): MyClass
    {
        return new MyClass;
    }
}

$test = new TestCoImplementation;
$object = $test->testCo();
var_dump($object);


// ----------

interface TestCon
{
    public function testCon(object $object): object;
}

class TestConImplementation implements TestCon
{
    public function testCon(MyClass $object): object
    {
        return $object;
    }
}

$test = new TestCoImplementation;
$object = $test->testCo(new MyClass);
var_dump($object);


Expected result:
----------------
I would hope that the Fatal Error is not present and that the second var_dump provides my class instance.

Actual result:
--------------
/Users/john/Desktop/contract_test.php:25:
class MyClass#2 (0) {
}
PHP Fatal error:  Declaration of TestConImplementation::testCon(MyClass $object): object must be compatible with TestCon::testCon(object $object): object in /Users/john/Desktop/contract_test.php on line 37
PHP Stack trace:
PHP   1. {main}() /Users/john/Desktop/contract_test.php:0

Fatal error: Declaration of TestConImplementation::testCon(MyClass $object): object must be compatible with TestCon::testCon(object $object): object in /Users/john/Desktop/contract_test.php on line 37

Call Stack:
    0.0026     399984   1. {main}() /Users/john/Desktop/contract_test.php:0