[Php84] Add rule for RoundingMode enum

[jorgsowa]

Adds new rule for replacing mode constants in the function round() with RoundingMode cases in PHP 8.4.

The PR is not finished, but please let me know whether it makes sense to add such a rule to the PHP8.4 ruleset.

Referenced RFC: https://wiki.php.net/rfc/correctly_name_the_rounding_mode_and_make_it_an_enum

[samsonasik]

Just a quick read, if I understand correctly, the constant is not deprecated (yet) in php 8.4, it just replaced in core code, so I think it is not really needed for now.

https://3v4l.org/Z40Kp/rfc#vgit.master

when on future, the constant will be deprecated, eg: on php 8.5, we can create the rule to migrate it, if this is accepted, we need to prepare immediatelly the Downgrade RoundingMode rules.

[jorgsowa]

It's unlikely that constants will be deprecated soon as it was the result of the RFC discussion. That's why I thought such a rule would help to speed up this process.

[samsonasik]

I prefer to have downgrade rule instead first then, as replace constant is not required, but once it upgraded to enum, it needs to have downgrade rule to back to constant

https://github.com/rectorphp/rector-downgrade-php

[jorgsowa]

Makes sense. I will create a downgrade rule then.

[samsonasik]

add $hasChanged flag here, so later can return null when no constant passed

Suggested change

	$args[2]->value = new Node\Expr\ClassConstFetch(new FullyQualified('RoundingMode'), $enumCase);
	$args[2]->value = new Node\Expr\ClassConstFetch(new FullyQualified('RoundingMode'), $enumCase);
	$hasChanged = true;

with init first before if above:

        $hasChanged = false;
        if ($modeArg instanceof ConstFetch) {

then later, before return node, it check $hasChanged flag:

if ($hasChanged) {
    return $node;
}

return null;