Fix phpstan/phpstan#10862: Invalid array key for constant array append when negative keys are used since PHP 8.3

src/Php/PhpVersion.php

@@ -511,4 +511,14 @@ public function throwsOnStringCast(): bool
 		return $this->versionId >= 70400;
 	}
 
+	public function updatesAutoIncrementKeyForNegativeValues(): bool
+	{
+		return $this->versionId >= 80300;
+	}
+
+	public function updatesAutoIncrementKeyForNegativeValuesInNonEmptyInitializer(): bool
+	{
+		return $this->versionId >= 80000;
+	}
+
 }

src/Reflection/InitializerExprTypeResolver.php

@@ -639,6 +639,9 @@ public function getArrayType(Expr\Array_ $expr, callable $getTypeCallback): Type
 		}
 
 		$arrayBuilder = ConstantArrayTypeBuilder::createEmpty();
+		if (count($expr->items) > 0) {
+			$arrayBuilder->setInitializedNonEmpty();
+		}
 		$isList = null;
 		$hasOffsetValueTypes = [];
 		foreach ($expr->items as $arrayItem) {

src/Type/Constant/ConstantArrayTypeBuilder.php

@@ -2,6 +2,7 @@
 
 namespace PHPStan\Type\Constant;
 
+use PHPStan\Reflection\PhpVersionStaticAccessor;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\AccessoryArrayListType;
@@ -41,6 +42,8 @@ final class ConstantArrayTypeBuilder
 
 	private bool $oversized = false;
 
+	private bool $initializedNonEmpty = false;
+
 	/**
 	 * @param list<Type> $keyTypes
 	 * @param array<int, Type> $valueTypes
@@ -62,6 +65,11 @@ public static function createEmpty(): self
 		return new self([], [], [0], [], TrinaryLogic::createYes());
 	}
 
+	public function setInitializedNonEmpty(): void
+	{
+		$this->initializedNonEmpty = true;
+	}
+
 	public static function createFromConstantArray(ConstantArrayType $startArrayType): self
 	{
 		$builder = new self(
@@ -209,7 +217,7 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $opt
 						$this->isList = TrinaryLogic::createNo();
 					}
 
-					if ($offsetValue >= $max) {
+					if ($this->shouldUpdateAutoIndex($offsetValue, $max)) {
 						/** @var int|float $newAutoIndex */
 						$newAutoIndex = $offsetValue + 1;
 						if (is_float($newAutoIndex)) {
@@ -419,4 +427,23 @@ public function isList(): bool
 		return $this->isList->yes();
 	}
 
+	private function shouldUpdateAutoIndex(int $offsetValue, int $max): bool
+	{
+		if ($offsetValue >= $max) {
+			return true;
+		}
+
+		if ($offsetValue >= 0 || $max !== 0) {
+			return false;
+		}
+
+		$phpVersion = PhpVersionStaticAccessor::getInstance();
+
+		if ($phpVersion->updatesAutoIncrementKeyForNegativeValues()) {
+			return true;
+		}
+
+		return $this->initializedNonEmpty && $phpVersion->updatesAutoIncrementKeyForNegativeValuesInNonEmptyInitializer();
+	}
+
 }

tests/PHPStan/Analyser/nsrt/bug-10862-php74.php

@@ -0,0 +1,26 @@
+<?php // lint < 8.0
+
+declare(strict_types = 1);
+
+namespace Bug10862Php74;
+
+use function PHPStan\Testing\assertType;
+
+// Pre-PHP 8.0: negative keys never affect auto-index
+
+// Imperative assignment
+function () {
+	$a = [];
+	$a[-4] = 1;
+	$a[] = 2;
+
+	assertType('array{-4: 1, 0: 2}', $a);
+};
+
+// Array literal
+function () {
+	$a = [-4 => 1];
+	$a[] = 2;
+
+	assertType('array{-4: 1, 0: 2}', $a);
+};

tests/PHPStan/Analyser/nsrt/bug-10862-php80.php

@@ -0,0 +1,23 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug10862Php80;
+
+use function PHPStan\Testing\assertType;
+
+// PHP 8.0+: array literal with negative keys updates auto-index
+
+function () {
+	$a = [-4 => 1];
+	$a[] = 2;
+
+	assertType('array{-4: 1, -3: 2}', $a);
+};
+
+function () {
+	$a = [-10 => 'a', -5 => 'b'];
+	$a[] = 'c';
+
+	assertType("array{-10: 'a', -5: 'b', -4: 'c'}", $a);
+};

tests/PHPStan/Analyser/nsrt/bug-10862-php82.php

@@ -0,0 +1,43 @@
+<?php // lint <= 8.2
+
+declare(strict_types = 1);
+
+namespace Bug10862Php82;
+
+use function PHPStan\Testing\assertType;
+
+// PHP <= 8.2: imperative assignment with negative keys does not affect auto-index
+
+function () {
+	$a = [];
+	$a[-4] = 1;
+	$a[] = 2;
+
+	assertType('array{-4: 1, 0: 2}', $a);
+};
+
+function () {
+	$a = [];
+	$a[-1] = 'x';
+	$a[] = 'y';
+
+	assertType("array{-1: 'x', 0: 'y'}", $a);
+};
+
+function () {
+	$a = [];
+	$a[-10] = 'a';
+	$a[-5] = 'b';
+	$a[] = 'c';
+
+	assertType("array{-10: 'a', -5: 'b', 0: 'c'}", $a);
+};
+
+function () {
+	$a = [];
+	$a[-3] = 'a';
+	$a[5] = 'b';
+	$a[] = 'c';
+
+	assertType("array{-3: 'a', 5: 'b', 6: 'c'}", $a);
+};

tests/PHPStan/Analyser/nsrt/bug-10862-php83.php

@@ -0,0 +1,59 @@
+<?php // lint >= 8.3
+
+declare(strict_types = 1);
+
+namespace Bug10862Php83;
+
+use function PHPStan\Testing\assertType;
+
+// PHP 8.3+: negative keys always affect auto-index (both imperative and literal)
+
+// Imperative assignment
+function () {
+	$a = [];
+	$a[-4] = 1;
+	$a[] = 2;
+
+	assertType('array{-4: 1, -3: 2}', $a);
+};
+
+function () {
+	$a = [];
+	$a[-1] = 'x';
+	$a[] = 'y';
+
+	assertType("array{-1: 'x', 0: 'y'}", $a);
+};
+
+function () {
+	$a = [];
+	$a[-10] = 'a';
+	$a[-5] = 'b';
+	$a[] = 'c';
+
+	assertType("array{-10: 'a', -5: 'b', -4: 'c'}", $a);
+};
+
+function () {
+	$a = [];
+	$a[-3] = 'a';
+	$a[5] = 'b';
+	$a[] = 'c';
+
+	assertType("array{-3: 'a', 5: 'b', 6: 'c'}", $a);
+};
+
+// Array literal
+function () {
+	$a = [-4 => 1];
+	$a[] = 2;
+
+	assertType('array{-4: 1, -3: 2}', $a);
+};
+
+function () {
+	$a = [-10 => 'a', -5 => 'b'];
+	$a[] = 'c';
+
+	assertType("array{-10: 'a', -5: 'b', -4: 'c'}", $a);
+};