--- /dev/null
+<?php
+
+/*
+ * This file is part of Psy Shell.
+ *
+ * (c) 2012-2017 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_ as ArrayNode;
+use PhpParser\Node\Expr\Assign as AssignNode;
+use PhpParser\Node\Expr\Empty_ as EmptyNode;
+use PhpParser\Node\Expr\FuncCall as FunctionCall;
+use PhpParser\Node\Expr\Isset_ as IssetNode;
+use PhpParser\Node\Expr\MethodCall;
+use PhpParser\Node\Expr\StaticCall;
+use Psy\Exception\FatalErrorException;
+
+/**
+ * Validate that the functions are used correctly.
+ *
+ * @author Martin HasoĊ <martin.hason@gmail.com>
+ */
+class FunctionReturnInWriteContextPass extends CodeCleanerPass
+{
+ const EXCEPTION_MESSAGE = "Can't use function return value in write context";
+
+ private $isPhp55;
+
+ public function __construct()
+ {
+ $this->isPhp55 = version_compare(PHP_VERSION, '5.5', '>=');
+ }
+
+ /**
+ * 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 function is used as an argument in the empty, only for PHP < 5.5
+ * @throws FatalErrorException if a value is assigned to a function
+ *
+ * @param Node $node
+ */
+ public function enterNode(Node $node)
+ {
+ if ($node instanceof ArrayNode || $this->isCallNode($node)) {
+ $items = $node instanceof ArrayNode ? $node->items : $node->args;
+ foreach ($items as $item) {
+ if ($item->byRef && $this->isCallNode($item->value)) {
+ throw new FatalErrorException(self::EXCEPTION_MESSAGE);
+ }
+ }
+ } elseif ($node instanceof IssetNode) {
+ foreach ($node->vars as $var) {
+ if (!$this->isCallNode($var)) {
+ continue;
+ }
+
+ if ($this->isPhp55) {
+ throw new FatalErrorException('Cannot use isset() on the result of a function call (you can use "null !== func()" instead)');
+ } else {
+ throw new FatalErrorException(self::EXCEPTION_MESSAGE);
+ }
+ }
+ } elseif ($node instanceof EmptyNode && !$this->isPhp55 && $this->isCallNode($node->expr)) {
+ throw new FatalErrorException(self::EXCEPTION_MESSAGE);
+ } elseif ($node instanceof AssignNode && $this->isCallNode($node->var)) {
+ throw new FatalErrorException(self::EXCEPTION_MESSAGE);
+ }
+ }
+
+ private function isCallNode(Node $node)
+ {
+ return $node instanceof FunctionCall || $node instanceof MethodCall || $node instanceof StaticCall;
+ }
+}