Bug #79754 [Opn->Nab]: Covariance fails with mixed type

Edit report at https://bugs.php.net/bug.php?id=79754&edit=1 ID: 79754 Updated by: derick@php.net Reported by: raincomplain at outlook dot com Summary: Covariance fails with mixed type -Status: Open +Status: Not a bug Type: Bug Package: Class/Object related PHP Version: 8.0.0alpha1 Block user comment: N Private report: N New Comment: Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php This is expected behaviour. If a return type is missing, it is the implicit union of "mixed|void". As "mixed|void" is a wider type than just "mixed", allowing it would break LSP. This is also explained in the RFC: https://wiki.php.net/rfc/mixed_type_v2#signature_checking_of_function_when_no_return_type_present Previous Comments: ------------------------------------------------------------------------ [2020-06-28 13:06:19] raincomplain at outlook dot com Description: ------------ Since mixed type indicates the absence of a type then one would assume that omitting a return type in a child class's method that returns mixed type in a parent class is fine! but PHP refuses to compile Test script: --------------- class Foo { function fun(): mixed { return 33; } } class Bar extends Foo { function fun() { return 33; } } Expected result: ---------------- The expected is to compile with no error Actual result: -------------- Fatal error: Declaration of Bar::fun() must be compatible with Foo::fun(): mixed ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=79754&edit=1