$arr = [$val] has type list{string|null}. After if ($arr === [null]), the else
branch has excluded the only value where the element is null, so $arr narrows to
list{string} and a call requiring list{string} should type-check. Analyzers diverge
on whether they perform this equality-based element subtraction on the array shape.
Source lead: Mago analyzer test array_reconcile (crates/analyzer/tests/cases),
function test_null_string_subtraction. Mago narrows and accepts the guarded call;
this file records every tool's verdict on the same construct.| Analyzer | Version | Result | Diagnostics |
|---|---|---|---|
| phan | 6.0.7Phan 6.0.7 php-ast version 1.1.3 PHP version used to run Phan: 8.5.9 | Pass | No diagnostics reported. |
| phpstan | 2.2.8PHPStan - PHP Static Analysis Tool 2.2.8 | Pass reported Lv.8+ | regressions_array_element_null_subtraction.php:35: Parameter #1 $arr of function Conformance\Tests\RegressionsArrayElementNullSubtraction\takesStringList expects array{string}, array{string|null} given. [identifier=argument.type] [reported-from-level=8]With strict-rulesregressions_array_element_null_subtraction.php:35: Parameter #1 $arr of function Conformance\Tests\RegressionsArrayElementNullSubtraction\takesStringList expects array{string}, array{string|null} given. [identifier=argument.type] |
| psalm | 6.16.1Psalm 6.16.1@f1f5de594dc76faf8784e02d3dc4716c91c6f6ac next: 7.0.0-beta19 |
Pass | regressions_array_element_null_subtraction.php:35: Argument 1 of Conformance\Tests\RegressionsArrayElementNullSubtraction\takesStringList expects list{string}, but parent type list{null|string} provided [ArgumentTypeCoercion] |
| mago | 1.46.0mago 1.46.0 | Pass | No diagnostics reported. |
| mir | 0.70.1mir 0.70.1 | Pass | No diagnostics reported. |
| phpantom | 0.9.0phpantom_lsp 0.9.0 | Pass | No diagnostics reported. |
| intelephense | 1.18.5intelephense 1.18.5 | Pass | No diagnostics reported. |
| phpy | 0.2.0phpy 0.2.0 | Pass | No diagnostics reported. |
| qodana | 262.8665.325Qodana 262.8665.325 | Fail | regressions_array_element_null_subtraction.php:20: Argument type does not match the declared [PhpDocSignatureInspection] Expectation diffLine 20: Unexpected errors ["Argument type does not match the declared [PhpDocSignatureInspection]"] |
| noverify | 0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529 | Pass | regressions_array_element_null_subtraction.php:21: param $arr miss matched with phpdoc type <<list{string}>> [funcParamTypeMissMatch] |
| steins | 0.1.5steins 0.1.5 (2026-08-12 revision 39b4cc1) | Pass | No diagnostics reported. |
| phpstan-strict | 2.2.8PHPStan - PHP Static Analysis Tool 2.2.8 | Pass | regressions_array_element_null_subtraction.php:35: Parameter #1 $arr of function Conformance\Tests\RegressionsArrayElementNullSubtraction\takesStringList expects array{string}, array{string|null} given. [identifier=argument.type] |
| psalm-next | 7.0.0-beta19Psalm 7.0.0-beta19@7e751c06a756fa64dc4c759c09fe4a173afcb433 | Pass | regressions_array_element_null_subtraction.php:35: Argument 1 of Conformance\Tests\RegressionsArrayElementNullSubtraction\takesStringList expects list{string}, but parent type list{null|string} provided [ArgumentTypeCoercion] |
<?php
declare(strict_types=1);
namespace Conformance\Tests\RegressionsArrayElementNullSubtraction;
/**
* Element-type narrowing by subtracting the null case.
*
* `$arr = [$val]` has type `list{string|null}`. After `if ($arr === [null])`, the else
* branch has excluded the only value where the element is null, so `$arr` narrows to
* `list{string}` and a call requiring `list{string}` should type-check. Analyzers diverge
* on whether they perform this equality-based element subtraction on the array shape.
*
* Source lead: Mago analyzer test `array_reconcile` (crates/analyzer/tests/cases),
* function `test_null_string_subtraction`. Mago narrows and accepts the guarded call;
* this file records every tool's verdict on the same construct.
*/
/** @param list{string} $arr */
function takesStringList(array $arr): void // E<noverify>: NoVerify cannot evaluate the list{string} shape param and flags the signature itself
{
printf("Count: %d\n", count($arr));
}
function caller(string|null $val): void
{
$arr = [$val];
if ($arr === [null]) {
// the only null-element value is excluded here
return;
}
takesStringList($arr); // E<phpstan>: does not subtract the null case via === [null], so $arr stays array{string|null} and reports argument.type // E<phpstan-strict>: same coercion under strict rules // E<psalm>: reports ArgumentTypeCoercion; element type stays string|null. Mago and Phan narrow to list{string} and stay clean
}