[DowngradePhp81] Follow parent return type on DowngradeNeverTypeDeclarationRector

[samsonasik]

Continue of #1390, when the class method implements interface method already has never type, eg:

interface Runnable
{
    public function run(): ?stdClass;
}

class ImplementorRunnable implements Runnable
{
    public function run(): never 
    {
        throw new \Exception('test');
    }
}

above code in php 8.1 is valid ref https://3v4l.org/npms1#v8.1rc3.

But when it downgraded, it currently produce to:

-    public function run(): \stdClass
+    /**
+     * @return never
+     */
+    public function run()

which will make Fatal error:

Fatal error: Declaration of ImplementorRunnable::run() must be compatible with Runnable::run(): ?stdClass

ref https://3v4l.org/aZ2cq#v8.1rc3

This PR try to fix it.

[samsonasik]

Fixed 🎉

[samsonasik]

All checks have passed 🎉 @TomasVotruba it is ready for review.

[TomasVotruba]

Thank you

[samsonasik]

It seems cause error on rector/rector repo:

Run php bin/rector list --ansi
Rector 96cf57b15bbc4e3b9d5f2f4b58820460c7de448e

Usage:
  command [options] [arguments]

PHP Fatal error:  Declaration of RectorPrefix20211205\Symfony\Component\String\UnicodeString::join($strings, $lastGlue = NULL): RectorPrefix20211205\Symfony\Component\String\UnicodeString must be compatible with RectorPrefix20211205\Symfony\Component\String\AbstractUnicodeString::join($strings, $lastGlue = NULL): RectorPrefix20211205\Symfony\Component\String\AbstractUnicodeString in /home/runner/work/rector/rector/vendor/symfony/string/UnicodeString.php on line 31
Fatal error: Declaration of RectorPrefix20211205\Symfony\Component\String\UnicodeString::join($strings, $lastGlue = NULL): RectorPrefix20211205\Symfony\Component\String\UnicodeString must be compatible with RectorPrefix20211205\Symfony\Component\String\AbstractUnicodeString::join($strings, $lastGlue = NULL): RectorPrefix20211205\Symfony\Component\String\AbstractUnicodeString in /home/runner/work/rector/rector/vendor/symfony/string/UnicodeString.php on line 31

https://github.com/rectorphp/rector/runs/4422515810?check_suite_focus=true#step:5:9

I will check.