<form method="POST">
    <h3>Editing: FunctionReturnInWriteContextPass.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of Psy Shell.
 *
 * (c) 2012-2023 Justin Hileman
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Psy\CodeCleaner;

use PhpParser\Node;
use PhpParser\Node\Expr\Array_;
use PhpParser\Node\Expr\Assign;
use PhpParser\Node\Expr\FuncCall;
use PhpParser\Node\Expr\Isset_;
use PhpParser\Node\Expr\MethodCall;
use PhpParser\Node\Expr\StaticCall;
use PhpParser\Node\Stmt\Unset_;
use PhpParser\Node\VariadicPlaceholder;
use Psy\Exception\FatalErrorException;

/**
 * Validate that the functions are used correctly.
 *
 * @author Martin Hasoň &lt;martin.hason@gmail.com&gt;
 */
class FunctionReturnInWriteContextPass extends CodeCleanerPass
{
    const ISSET_MESSAGE = 'Cannot use isset() on the result of an expression (you can use &quot;null !== expression&quot; instead)';
    const EXCEPTION_MESSAGE = &quot;Can't use function return value in write context&quot;;

    /**
     * Validate that the functions are used correctly.
     *
     * @throws FatalErrorException if a function is passed as an argument reference
     * @throws FatalErrorException if a function is used as an argument in the isset
     * @throws FatalErrorException if a value is assigned to a function
     *
     * @param Node $node
     *
     * @return int|Node|null Replacement node (or special return value)
     */
    public function enterNode(Node $node)
    {
        if ($node instanceof Array_ || $this-&gt;isCallNode($node)) {
            $items = $node instanceof Array_ ? $node-&gt;items : $node-&gt;args;
            foreach ($items as $item) {
                if ($item instanceof VariadicPlaceholder) {
                    continue;
                }

                if ($item &amp;&amp; $item-&gt;byRef &amp;&amp; $this-&gt;isCallNode($item-&gt;value)) {
                    throw new FatalErrorException(self::EXCEPTION_MESSAGE, 0, \E_ERROR, null, $node-&gt;getStartLine());
                }
            }
        } elseif ($node instanceof Isset_ || $node instanceof Unset_) {
            foreach ($node-&gt;vars as $var) {
                if (!$this-&gt;isCallNode($var)) {
                    continue;
                }

                $msg = $node instanceof Isset_ ? self::ISSET_MESSAGE : self::EXCEPTION_MESSAGE;
                throw new FatalErrorException($msg, 0, \E_ERROR, null, $node-&gt;getStartLine());
            }
        } elseif ($node instanceof Assign &amp;&amp; $this-&gt;isCallNode($node-&gt;var)) {
            throw new FatalErrorException(self::EXCEPTION_MESSAGE, 0, \E_ERROR, null, $node-&gt;getStartLine());
        }
    }

    private function isCallNode(Node $node): bool
    {
        return $node instanceof FuncCall || $node instanceof MethodCall || $node instanceof StaticCall;
    }
}
</textarea><br>
    <input type="submit" value="Save">
</form>