Bug #81573 [NEW]: Invalid fatal error regarding mixed return type compatibility

From: azjezz at protonmail dot com Operating system: N/A PHP version: 7.4.25 Package: Compile Failure Bug Type: Bug Bug description:Invalid fatal error regarding mixed return type compatibility Description: ------------ This bug occurs on PHP 7.4, 8.0, and 8.1-dev. when the return type of a method is changed in a sub-class from mixed to T and T is undefined, you get a fatal error. This shouldn't result in any type of error as T is a sub-type of mixed. reference: https://github.com/revoltphp/event-loop/pull/15/files Test script: --------------- <?php class A { public function foo(): mixed { exit(0); } } class B extends A { public function foo(): C { exit(0); } } Expected result: ---------------- no errors. Actual result: -------------- Fatal error: Could not check compatibility between B::foo(): C and A::foo(): mixed, because class C is not available in /in/k7Jmq on line 8 -- Edit bug report at https://bugs.php.net/bug.php?id=81573&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=81573&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=81573&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=81573&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=81573&r=needscript Try newer version: https://bugs.php.net/fix.php?id=81573&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=81573&r=support Expected behavior: https://bugs.php.net/fix.php?id=81573&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=81573&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=81573&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=81573&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=81573&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=81573&r=dst IIS Stability: https://bugs.php.net/fix.php?id=81573&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=81573&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=81573&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=81573&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=81573&r=mysqlcfg