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Optional-key shapes stay list-compatible

Group: Cross-analyzer regressions · Category: regression · File: regressions_optional_key_shape_is_list.php

Analyzer results

regressions_optional_key_shape_is_list.php:29: Type array{a?: string} for $a is never list<mixed> [TypeDoesNotContainType]
regressions_optional_key_shape_is_list.php:37: Type array{a?: string} for $a is never list<mixed> [TypeDoesNotContainType]

regressions_optional_key_shape_is_list.php:29: RedundantCondition: Condition is always false, so the then branch is never reached [MIR0400]

regressions_optional_key_shape_is_list.php:27: param $a miss matched with phpdoc type <<array{a?: string}>> [funcParamTypeMissMatch]
regressions_optional_key_shape_is_list.php:35: param $a miss matched with phpdoc type <<array{a?: string}>> [funcParamTypeMissMatch]

regressions_optional_key_shape_is_list.php:29: Type array{a?: string} for $a is never list<mixed> [TypeDoesNotContainType]
regressions_optional_key_shape_is_list.php:37: Type array{a?: string} for $a is never list<mixed> [TypeDoesNotContainType]

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\RegressionsOptionalKeyShapeIsList;

/**
 * Optional-key shapes stay list-compatible.
 *
 * A shape whose only keys are optional (for example `array{a?: string}`) includes `[]`
 * as a valid value, and `array_is_list([]) === true`. So `array_is_list($a)` is
 * undecidable (maybe true), not "always false", and narrowing to a list is reachable.
 *
 * Several analyzers historically treated the optional string key as required and
 * collapsed the list check to "always false" / "impossible". PHPStan fixed this
 * in 2.2.9 (phpstan-src#6025). Mago is silent since 1.43. Phan reports the check
 * as "maybe", which is the runtime-correct verdict.
 *
 * References:
 * - PHPStan  https://github.com/phpstan/phpstan/issues/14938  (fix: phpstan-src#6025, 2.2.9)
 * - Psalm    https://github.com/vimeo/psalm/issues/11905      (open)
 * - Mago     https://github.com/carthage-software/mago/issues/2073 (fixed in 1.43)
 * - Cross-tool survey https://github.com/phpstan/phpstan/discussions/14939
 */

/** @param array{a?: string} $a */
function optionalStringKeyIsList(array $a): void // E<noverify>: NoVerify does not parse array shape syntax and flags the annotation itself, not the list narrowing
{
    if (array_is_list($a)) { // E<psalm>: TypeDoesNotContainType, reported as never list<mixed> (#11905) // E<pzoom>: same TypeDoesNotContainType as Psalm // E<mir>: RedundantCondition — collapses the check. PHPStan reported always-false through 2.2.8 (#14938) and is silent since 2.2.9. Mago reported impossible-type-comparison in 1.19 and is silent since 1.43 (#2073), which is the runtime-correct verdict
        echo "reached at runtime when \$a === []\n";
    }
}

/** @param array{a?: string} $a */
function optionalStringKeyAssertList(array $a): void // E<noverify>: NoVerify does not parse array shape syntax and flags the annotation itself, not the list narrowing
{
    assert(array_is_list($a)); // E<psalm>: TypeDoesNotContainType, reported as never list<mixed> (#11905) // E<pzoom>: same TypeDoesNotContainType as Psalm. PHPStan reported always-false through 2.2.8 (#14938) and is silent since 2.2.9. Mago is silent since 1.43 (#2073)
}

optionalStringKeyIsList([]);
optionalStringKeyAssertList([]);