Hello. I was trying the new release 9.1.0 and I realized that the ForbiddenThisUseContextsSniff currently generating more false positives than actual issues.

Following use case currently resulting with an issue while it's completely valid:

<?php

class MyBar extends ArrayObject
{
    protected $x = array('aa', 'bb');

    public function remove($name)
    {
        if (isset($this[$name])) {
            unset($this[$name]);
            return true;
        }

        return false;
    }
}

(new MyBar())->remove('x');

producing:

"$this" can no longer be unset since PHP 7.1.

Is this intended behavior? If its not, sounds like a problem inside this case block: https://github.com/PHPCompatibility/PHPCompatibility/blob/master/PHPCompatibility/Sniffs/Variables/ForbiddenThisUseContextsSniff.php#L248 I tried to follow the flow but could not figure out a proper solution without affecting other use cases.

If someone can assist me with some tips, I would like to create a PR to reduce related false positives.