Description:
------------
Type errors thrown for union typehints containing self in an anonymous class contain only class@anonymous in the error message, without the full typehint.

Test script:
---------------
class a {
    public function test(): self|string
    {
        return new \stdClass;
    }
};

$b = new class {
    public function test(): self|string
    {
        return new \stdClass;
    }
};

try {
    (new a)->test();
} catch (\Throwable $e) {
    echo $e->getMessage().PHP_EOL;
}

try {
    $b->test();
} catch (\Throwable $e) {
    echo $e->getMessage().PHP_EOL;
}


Expected result:
----------------
a::test(): Return value must be of type a|string, stdClass returned
class@anonymous::test(): Return value must be of type class@anonymous|string, stdClass returned

Actual result:
--------------
a::test(): Return value must be of type a|string, stdClass returned
class@anonymous::test(): Return value must be of type class@anonymous, stdClass returned