Description:
------------
When inheriting from an abstract class, a method implemented by a trait does not allow adding a return type. This is allowed when the method is implemented directly in the child class.

On the current master (7.2) the same happens when omitting a type-hint.

With interfaces the behavior is consistent with or without traits.

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

abstract class L1{ 
abstract function m3($x);
} 

trait L2t{ 
function m3($x): int{}
} 

class L2 extends L1{ 
use L2t; 
}

Expected result:
----------------
N/A

Actual result:
--------------
Fatal error: Declaration of L2t::m3($x): int must be compatible with L1::m3($x) in ...