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Merged
ondrejmirtes merged 2 commits into from
Sep 27, 2026
Merged

Keep an empty array next to an oversized array in a union #6609

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71cb8ca
Keep an empty array next to an oversized array in a union
ondrejmirtes Sep 26, 2026
3bc4b93
Bump expected turbo version
ondrejmirtes Sep 27, 2026
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Keep an empty array next to an oversized array in a union 
reduceArrays() leaves empty constant arrays out when it generalizes to an
oversized array, but a union of an array that already is oversized with
array{} went through processArrayTypes(), which folded array{} into it:
the oversized accessory then rejected [] (a false positive for T inferred
from both) and non-empty-array accepted the union (a missed error).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VpbB99tJfUmeArX74xqvHv
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@ondrejmirtes @claude
ondrejmirtes and claude committed Sep 27, 2026
commit 71cb8ca943f507a43b3ebebf847eee8e445ccc67
38 changes: 38 additions & 0 deletions src/Type/TypeCombinator.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1037,6 +1037,28 @@ private static function processArrayAccessoryTypes(array $arrayTypes): array
return $commonAccessoryTypes;
}

/**
* @param Type[] $arrayTypes
*/
private static function findEmptyArrayNextToOversizedArray(array $arrayTypes): ?Type
{
if (count($arrayTypes) < 2) {
return null;
}

$emptyArray = null;
$hasOversizedArray = false;
foreach ($arrayTypes as $arrayType) {
if ($arrayType->isOversizedArray()->yes()) {
$hasOversizedArray = true;
} elseif ($emptyArray === null && $arrayType->isConstantArray()->yes() && $arrayType->isIterableAtLeastOnce()->no()) {
$emptyArray = $arrayType;
}
}

return $hasOversizedArray ? $emptyArray : null;
}

/**
* @param list<Type> $arrayTypes
* @return Type[]
Expand All @@ -1047,6 +1069,22 @@ private static function processArrayTypes(array $arrayTypes): array
return [];
}

$emptyArray = self::findEmptyArrayNextToOversizedArray($arrayTypes);
if ($emptyArray !== null) {
// like reduceArrays() does when it generalizes to an oversized array:
// folded into it, the empty array would be lost to the oversized
// accessory, which accepts only arrays that hold something
$otherArrayTypes = [];
foreach ($arrayTypes as $arrayType) {
if ($arrayType->isConstantArray()->yes() && $arrayType->isIterableAtLeastOnce()->no()) {
continue;
}
$otherArrayTypes[] = $arrayType;
}

return [$emptyArray, ...self::processArrayTypes($otherArrayTypes)];
}

$accessoryTypes = self::processArrayAccessoryTypes($arrayTypes);

if (count($arrayTypes) === 1) {
Expand Down
273 changes: 273 additions & 0 deletions tests/PHPStan/Analyser/nsrt/oversized-array-union-with-empty-array.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,273 @@
<?php declare(strict_types = 1);

namespace OversizedArrayUnionWithEmptyArray;

use function PHPStan\Testing\assertType;

function doFoo(bool $flag): void
{
$big = [
'K0' => 'v0',
'K1' => 'v1',
'K2' => 'v2',
'K3' => 'v3',
'K4' => 'v4',
'K5' => 'v5',
'K6' => 'v6',
'K7' => 'v7',
'K8' => 'v8',
'K9' => 'v9',
'K10' => 'v10',
'K11' => 'v11',
'K12' => 'v12',
'K13' => 'v13',
'K14' => 'v14',
'K15' => 'v15',
'K16' => 'v16',
'K17' => 'v17',
'K18' => 'v18',
'K19' => 'v19',
'K20' => 'v20',
'K21' => 'v21',
'K22' => 'v22',
'K23' => 'v23',
'K24' => 'v24',
'K25' => 'v25',
'K26' => 'v26',
'K27' => 'v27',
'K28' => 'v28',
'K29' => 'v29',
'K30' => 'v30',
'K31' => 'v31',
'K32' => 'v32',
'K33' => 'v33',
'K34' => 'v34',
'K35' => 'v35',
'K36' => 'v36',
'K37' => 'v37',
'K38' => 'v38',
'K39' => 'v39',
'K40' => 'v40',
'K41' => 'v41',
'K42' => 'v42',
'K43' => 'v43',
'K44' => 'v44',
'K45' => 'v45',
'K46' => 'v46',
'K47' => 'v47',
'K48' => 'v48',
'K49' => 'v49',
'K50' => 'v50',
'K51' => 'v51',
'K52' => 'v52',
'K53' => 'v53',
'K54' => 'v54',
'K55' => 'v55',
'K56' => 'v56',
'K57' => 'v57',
'K58' => 'v58',
'K59' => 'v59',
'K60' => 'v60',
'K61' => 'v61',
'K62' => 'v62',
'K63' => 'v63',
'K64' => 'v64',
'K65' => 'v65',
'K66' => 'v66',
'K67' => 'v67',
'K68' => 'v68',
'K69' => 'v69',
'K70' => 'v70',
'K71' => 'v71',
'K72' => 'v72',
'K73' => 'v73',
'K74' => 'v74',
'K75' => 'v75',
'K76' => 'v76',
'K77' => 'v77',
'K78' => 'v78',
'K79' => 'v79',
'K80' => 'v80',
'K81' => 'v81',
'K82' => 'v82',
'K83' => 'v83',
'K84' => 'v84',
'K85' => 'v85',
'K86' => 'v86',
'K87' => 'v87',
'K88' => 'v88',
'K89' => 'v89',
'K90' => 'v90',
'K91' => 'v91',
'K92' => 'v92',
'K93' => 'v93',
'K94' => 'v94',
'K95' => 'v95',
'K96' => 'v96',
'K97' => 'v97',
'K98' => 'v98',
'K99' => 'v99',
'K100' => 'v100',
'K101' => 'v101',
'K102' => 'v102',
'K103' => 'v103',
'K104' => 'v104',
'K105' => 'v105',
'K106' => 'v106',
'K107' => 'v107',
'K108' => 'v108',
'K109' => 'v109',
'K110' => 'v110',
'K111' => 'v111',
'K112' => 'v112',
'K113' => 'v113',
'K114' => 'v114',
'K115' => 'v115',
'K116' => 'v116',
'K117' => 'v117',
'K118' => 'v118',
'K119' => 'v119',
'K120' => 'v120',
'K121' => 'v121',
'K122' => 'v122',
'K123' => 'v123',
'K124' => 'v124',
'K125' => 'v125',
'K126' => 'v126',
'K127' => 'v127',
'K128' => 'v128',
'K129' => 'v129',
'K130' => 'v130',
'K131' => 'v131',
'K132' => 'v132',
'K133' => 'v133',
'K134' => 'v134',
'K135' => 'v135',
'K136' => 'v136',
'K137' => 'v137',
'K138' => 'v138',
'K139' => 'v139',
'K140' => 'v140',
'K141' => 'v141',
'K142' => 'v142',
'K143' => 'v143',
'K144' => 'v144',
'K145' => 'v145',
'K146' => 'v146',
'K147' => 'v147',
'K148' => 'v148',
'K149' => 'v149',
'K150' => 'v150',
'K151' => 'v151',
'K152' => 'v152',
'K153' => 'v153',
'K154' => 'v154',
'K155' => 'v155',
'K156' => 'v156',
'K157' => 'v157',
'K158' => 'v158',
'K159' => 'v159',
'K160' => 'v160',
'K161' => 'v161',
'K162' => 'v162',
'K163' => 'v163',
'K164' => 'v164',
'K165' => 'v165',
'K166' => 'v166',
'K167' => 'v167',
'K168' => 'v168',
'K169' => 'v169',
'K170' => 'v170',
'K171' => 'v171',
'K172' => 'v172',
'K173' => 'v173',
'K174' => 'v174',
'K175' => 'v175',
'K176' => 'v176',
'K177' => 'v177',
'K178' => 'v178',
'K179' => 'v179',
'K180' => 'v180',
'K181' => 'v181',
'K182' => 'v182',
'K183' => 'v183',
'K184' => 'v184',
'K185' => 'v185',
'K186' => 'v186',
'K187' => 'v187',
'K188' => 'v188',
'K189' => 'v189',
'K190' => 'v190',
'K191' => 'v191',
'K192' => 'v192',
'K193' => 'v193',
'K194' => 'v194',
'K195' => 'v195',
'K196' => 'v196',
'K197' => 'v197',
'K198' => 'v198',
'K199' => 'v199',
'K200' => 'v200',
'K201' => 'v201',
'K202' => 'v202',
'K203' => 'v203',
'K204' => 'v204',
'K205' => 'v205',
'K206' => 'v206',
'K207' => 'v207',
'K208' => 'v208',
'K209' => 'v209',
'K210' => 'v210',
'K211' => 'v211',
'K212' => 'v212',
'K213' => 'v213',
'K214' => 'v214',
'K215' => 'v215',
'K216' => 'v216',
'K217' => 'v217',
'K218' => 'v218',
'K219' => 'v219',
'K220' => 'v220',
'K221' => 'v221',
'K222' => 'v222',
'K223' => 'v223',
'K224' => 'v224',
'K225' => 'v225',
'K226' => 'v226',
'K227' => 'v227',
'K228' => 'v228',
'K229' => 'v229',
'K230' => 'v230',
'K231' => 'v231',
'K232' => 'v232',
'K233' => 'v233',
'K234' => 'v234',
'K235' => 'v235',
'K236' => 'v236',
'K237' => 'v237',
'K238' => 'v238',
'K239' => 'v239',
'K240' => 'v240',
'K241' => 'v241',
'K242' => 'v242',
'K243' => 'v243',
'K244' => 'v244',
'K245' => 'v245',
'K246' => 'v246',
'K247' => 'v247',
'K248' => 'v248',
'K249' => 'v249',
'K250' => 'v250',
'K251' => 'v251',
'K252' => 'v252',
'K253' => 'v253',
'K254' => 'v254',
'K255' => 'v255',
'K256' => 'v256',
'K257' => 'v257',
'K258' => 'v258',
'K259' => 'v259',
];
assertType("array{}|(non-empty-array<literal-string&non-falsy-string&uppercase-string, literal-string&lowercase-string&non-falsy-string>&oversized-array)", $flag ? $big : []);
assertType("array{}|(non-empty-array<literal-string&non-falsy-string&uppercase-string, literal-string&lowercase-string&non-falsy-string>&oversized-array)", $flag ? [] : $big);
}
11 changes: 11 additions & 0 deletions tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -3268,4 +3268,15 @@ public function testRoundModePhp84(): void
]);
}

public function testOversizedArrayUnionWithEmptyArray(): void
{
$this->analyse([__DIR__ . '/data/oversized-array-union-with-empty-array.php'], [
[
'Parameter #1 $a of function OversizedArrayUnionWithEmptyArrayRule\\nonEmpty expects non-empty-array<string, string>, array{}|(non-empty-array<literal-string&non-falsy-string, literal-string&non-falsy-string>) given.',
286,
'array{}|(non-empty-array<literal-string&non-falsy-string, literal-string&non-falsy-string>) might be empty.',
],
]);
}

}
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