Incorrect behavior of SimplifyUselessVariableRector

[Andi-aboalarm]

Bug Report

Subject	Details
Rector version	last dev-main
Installed as	composer dependency

Minimal PHP Code Causing Issue

See https://getrector.com/demo/3adaf502-2201-47e4-aaa2-33984f3bfdfd

<?php

final class DemoFile
{
    public function run()
    {
        $foo = null;
        $bar = strlen($foo);
        return $bar;
    }
}

Responsible rules

• SimplifyUselessVariableRector

Expected Behavior

<?php

final class DemoFile
{
    public function run()
    {
        $foo = null;
        return strlen($foo ?? '');
    }
}

[Andi-aboalarm]

null coalescing operator needed to avoid null in strlen to avoid deprecation warning

[samsonasik]

SimplifyUselessVariableRector is unrelated with null coalescing transformation.

Also, Rector is not error handler, use phpstan job as the right tool to get there, and decide what need to do in the code ( check is_null, ,is_string, or just remove the code, etc) :)

[samsonasik]

Actually, if you have possibly null value for strlen() on php 8.1, you can use NullToStrictStringFuncCallArgRector that included in LevelSetList::UP_TO_PHP_81 so it converted with cast (string) https://getrector.com/demo/054ffe95-48fc-497d-94c1-a1d76a92538e

[samsonasik]

Re-open, I created PR rectorphp/rector-src#3385 for it to handle $variable = null early defined before passed as arg on NullToStrictStringFuncCallArgRector