Description:
------------
Greetings,

I believe the following should be allowed.

class Animal {}

class Cat extends Animal {}

class My1 {
    public function getAnimal () : Animal {}
}

class My2 extends My1 {
    public function getAnimal () : Cat {}
}

Because Cat is a Animal and thus compatible with the inherited signature.

Thanks in advance.

Expected result:
----------------
No errors

Actual result:
--------------
Compile error