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Array elements written through a foreach reference update the array type

Group: Arrays and shapes · Category: phpdoc · File: arrays_written_by_reference.php

After foreach ($ints as &$item) { $item = 'x'; }, $ints is no longer a list<int>. A tool that types the reference as int but never writes that back into the array still accepts takesIntList($ints). Source: vimeo/psalm#12154 (7.0.0-rc2). References: - psalm#12154

Analyzer results

AnalyzerVersionResultDiagnostics
phan 6.0.11Phan 6.0.11 php-ast version 1.1.3 PHP version used to run Phan: 8.5.11 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
phpstan 2.3.5PHPStan - PHP Static Analysis Tool 2.3.5 Pass reported Lv.7+ 
arrays_written_by_reference.php:40: Parameter #1 $ints of function Conformance\Tests\ArraysWrittenByReference\takesIntList expects list<int>, list<'x'|int> given. [reported-from-level=7]
With strict-rules
arrays_written_by_reference.php:40: Parameter #1 $ints of function Conformance\Tests\ArraysWrittenByReference\takesIntList expects list<int>, list<'x'|int> given.
psalm 6.20.9Psalm 6.20.9@f67170ac3c3b931f5088681e21d6c8babc601c08
next: 7.0.4		 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
mago 1.59.0mago 1.59.0 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
mir 0.91.0mir 0.91.0 Pass 
arrays_written_by_reference.php:40: InvalidArgument: Argument $ints of takesIntList() expects 'list<int>', got 'list<"x">' [MIR0201]
phpantom 0.11.1phpantom_lsp 0.11.1 Pass 
arrays_written_by_reference.php:40: Argument 1 ($ints) expects list<int>, got list<'x'> [type_mismatch_argument]
intelephense 1.18.5intelephense 1.18.5 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
phpactor 2026.10.07.0Phpactor 2026.10.07.0 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
phpy 1.0.19490phpy 1.0.19490 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
qodana 262.11879.104PhpStorm 262.11879.104 Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
noverify 0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529 Fail 
arrays_written_by_reference.php:23: param $ints miss matched with phpdoc type <<list<int>>> [funcParamTypeMissMatch]
arrays_written_by_reference.php:30: param $ints miss matched with phpdoc type <<list<int>>> [funcParamTypeMissMatch]
Expectation diff
Line 40: Expected 1 error(s)
Line 23: Unexpected errors ["param $ints miss matched with phpdoc type <<list<int>>> [funcParamTypeMissMatch]"]
Line 30: Unexpected errors ["param $ints miss matched with phpdoc type <<list<int>>> [funcParamTypeMissMatch]"]
steins 0.1.8steins 0.1.8 (2026-09-21 revision 76306a9) Fail

No diagnostics reported.

Expectation diff
Line 40: Expected 1 error(s)
phpstan-strict 2.3.5PHPStan - PHP Static Analysis Tool 2.3.5 Pass 
arrays_written_by_reference.php:40: Parameter #1 $ints of function Conformance\Tests\ArraysWrittenByReference\takesIntList expects list<int>, list<'x'|int> given.
psalm-next 7.0.4Psalm 7.0.4@fa5b1f6e665cb743838ffd865b8fc96207f9409f Pass 
arrays_written_by_reference.php:40: Argument 1 of Conformance\Tests\ArraysWrittenByReference\takesIntList expects list<int>, but list<'x'|int> provided [InvalidArgument]

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\ArraysWrittenByReference;

/**
 * Array elements written through a foreach reference update the array type.
 *
 * After `foreach ($ints as &$item) { $item = 'x'; }`, `$ints` is no longer
 * a `list<int>`. A tool that types the reference as `int` but never writes
 * that back into the array still accepts `takesIntList($ints)`.
 *
 * Source: vimeo/psalm#12154 (7.0.0-rc2).
 *
 * References:
 * - https://github.com/vimeo/psalm/pull/12154
 */

/**
 * @param list<int> $ints
 */
function takesIntList(array $ints): void
{
}

/**
 * @param list<int> $ints
 */
function writesStringThroughReference(array $ints): void
{
    $before = $ints;
    takesIntList($before); // V

    foreach ($ints as &$item) {
        $item = 'x';
    }
    unset($item);

    takesIntList($ints); // E: the array now holds strings
}