1--TEST-- 2Invalid union type variance: Using parent of class in return type 3--FILE-- 4<?php 5 6class X {} 7class Y extends X {} 8 9class A { 10 public function method(): Y|string {} 11} 12class B extends A { 13 public function method(): X|string {} 14} 15 16?> 17--EXPECTF-- 18Fatal error: Declaration of B::method(): X|string must be compatible with A::method(): Y|string in %s on line %d 19