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PassableByReferencePass.php
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<?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;
use PhpParser\Node\Expr\Array_;
use PhpParser\Node\Expr\ArrayDimFetch;
use PhpParser\Node\Expr\ClassConstFetch;
use PhpParser\Node\Expr\FuncCall;
use PhpParser\Node\Expr\MethodCall;
use PhpParser\Node\Expr\PropertyFetch;
use PhpParser\Node\Expr\StaticCall;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\VariadicPlaceholder;
use Psy\Exception\FatalErrorException;
/**
* Validate that only variables (and variable-like things) are passed by reference.
*/
class PassableByReferencePass extends CodeCleanerPass
{
const EXCEPTION_MESSAGE = 'Only variables can be passed by reference';
/**
* @throws FatalErrorException if non-variables are passed by reference
*
* @param Node $node
*
* @return int|Node|null Replacement node (or special return value)
*/
public function enterNode(Node $node)
{
// @todo support MethodCall and StaticCall as well.
if ($node instanceof FuncCall) {
// if function name is an expression or a variable, give it a pass for now.
if ($node->name instanceof Expr || $node->name instanceof Variable) {
return;
}
$name = (string) $node->name;
if ($name === 'array_multisort') {
return $this->validateArrayMultisort($node);
}
try {
$refl = new \ReflectionFunction($name);
} catch (\ReflectionException $e) {
// Well, we gave it a shot!
return;
}
$args = [];
foreach ($node->args as $position => $arg) {
if ($arg instanceof VariadicPlaceholder) {
continue;
}
$args[$arg->name !== null ? $arg->name->name : $position] = $arg;
}
foreach ($refl->getParameters() as $key => $param) {
if (\array_key_exists($key, $args) || \array_key_exists($param->name, $args)) {
$arg = $args[$param->name] ?? $args[$key];
if ($param->isPassedByReference() && !$this->isPassableByReference($arg)) {
throw new FatalErrorException(self::EXCEPTION_MESSAGE, 0, \E_ERROR, null, $node->getStartLine());
}
}
}
}
}
private function isPassableByReference(Node $arg): bool
{
// Unpacked arrays can be passed by reference
if ($arg->value instanceof Array_) {
return $arg->unpack;
}
// FuncCall, MethodCall and StaticCall are all PHP _warnings_ not fatal errors, so we'll let
// PHP handle those ones :)
return $arg->value instanceof ClassConstFetch ||
$arg->value instanceof PropertyFetch ||
$arg->value instanceof Variable ||
$arg->value instanceof FuncCall ||
$arg->value instanceof MethodCall ||
$arg->value instanceof StaticCall ||
$arg->value instanceof ArrayDimFetch;
}
/**
* Because array_multisort has a problematic signature...
*
* The argument order is all sorts of wonky, and whether something is passed
* by reference or not depends on the values of the two arguments before it.
* We'll do a good faith attempt at validating this, but err on the side of
* permissive.
*
* This is why you don't design languages where core code and extensions can
* implement APIs that wouldn't be possible in userland code.
*
* @throws FatalErrorException for clearly invalid arguments
*
* @param Node $node
*/
private function validateArrayMultisort(Node $node)
{
$nonPassable = 2; // start with 2 because the first one has to be passable by reference
foreach ($node->args as $arg) {
if ($this->isPassableByReference($arg)) {
$nonPassable = 0;
} elseif (++$nonPassable > 2) {
// There can be *at most* two non-passable-by-reference args in a row. This is about
// as close as we can get to validating the arguments for this function :-/
throw new FatalErrorException(self::EXCEPTION_MESSAGE, 0, \E_ERROR, null, $node->getStartLine());
}
}
}
}

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