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Do not generalize a union of constant arrays that is no bigger than its largest member in TypeCombinator::optimizeConstantArrays() #6829

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Do not generalize a union of constant arrays that is no bigger than its largest member in TypeCombinator::optimizeConstantArrays() #6829

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33 changes: 29 additions & 4 deletions src/Type/TypeCombinator.php
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@
use function get_class;
use function implode;
use function in_array;
use function max;
use function spl_object_id;
use function sprintf;
use function usort;
Expand Down Expand Up @@ -1221,7 +1222,7 @@ private static function processArrayTypes(array $arrayTypes): array

$arrayType = new ArrayType(
self::union(...$keyTypesForGeneralArray),
self::union(...self::optimizeConstantArrays($valueTypesForGeneralArray)),
self::union(...self::optimizeConstantArrays($valueTypesForGeneralArray, $valueTypesForGeneralArray)),
);

if ($templateArrayType !== null) {
Expand All @@ -1240,7 +1241,7 @@ private static function processArrayTypes(array $arrayTypes): array
];
}

$reducedArrayTypes = self::optimizeConstantArrays(self::reduceArrays($arrayTypes, true));
$reducedArrayTypes = self::optimizeConstantArrays(self::reduceArrays($arrayTypes, true), $arrayTypes);
foreach ($reducedArrayTypes as $idx => $reducedArray) {
$applied = $accessoryTypes;
if ($reducedArray->isIterableAtLeastOnce()->no()) {
Expand All @@ -1259,17 +1260,41 @@ private static function processArrayTypes(array $arrayTypes): array
}

/**
* The count of constant array value types above which a union of the given
* types gets generalized. A single type already holding more than
* ARRAY_COUNT_LIMIT of them raises it - a union no bigger than one of its
* members does not grow the type, generalizing it would only lose precision.
*
* @param Type[] $types
*/
private static function getConstantArrayValueTypesLimit(array $types): int
{
$limit = ConstantArrayTypeBuilder::ARRAY_COUNT_LIMIT;
foreach ($types as $type) {
$limit = max($limit, self::countConstantArrayValueTypes([$type]));
}

return $limit;
}

/**
* @param Type[] $types
* @param Type[] $unionedTypes the types whose union $types represent
* @return Type[]
*/
private static function optimizeConstantArrays(array $types): array
private static function optimizeConstantArrays(array $types, array $unionedTypes): array
{
$constantArrayValuesCount = self::countConstantArrayValueTypes($types);

if ($constantArrayValuesCount <= ConstantArrayTypeBuilder::ARRAY_COUNT_LIMIT) {
return $types;
}

$limit = self::getConstantArrayValueTypesLimit($unionedTypes);
if ($constantArrayValuesCount <= $limit) {
return $types;
}

// Stage 1: collapse same-key-set ConstantArrayType variants per-position
// before the (lossy) generalization below kicks in. Variants with the
// same key signature mergeWith losslessly into a single shape whose
Expand Down Expand Up @@ -1311,7 +1336,7 @@ private static function optimizeConstantArrays(array $types): array
if ($anyMerged) {
$types = array_values($collapsed);
$constantArrayValuesCount = self::countConstantArrayValueTypes($types);
if ($constantArrayValuesCount <= ConstantArrayTypeBuilder::ARRAY_COUNT_LIMIT) {
if ($constantArrayValuesCount <= $limit) {
return $types;
}
}
Expand Down
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