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