1--TEST-- 2Return type covariance; extends abstract class 3--FILE-- 4<?php 5 6abstract class A { 7 abstract function foo(): A; 8} 9 10class B extends A { 11 function foo(): StdClass {} 12} 13--EXPECTF-- 14Fatal error: Declaration of B::foo(): StdClass must be compatible with A::foo(): A in %s on line %d 15