Ignore negative keys on checking whether a ConstantArray is a list

src/Type/Constant/ConstantArrayTypeBuilder.php

@@ -165,16 +165,22 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $opt
 				if ($offsetType instanceof ConstantIntegerType) {
 					$min = min($this->nextAutoIndexes);
 					$max = max($this->nextAutoIndexes);
-					if ($offsetType->getValue() > $min) {
-						if ($offsetType->getValue() <= $max) {
-							$this->isList = $this->isList->and(TrinaryLogic::createMaybe());
-						} else {
-							$this->isList = TrinaryLogic::createNo();
+					$offsetValue = $offsetType->getValue();
+					if ($offsetValue >= 0) {
+						if ($offsetValue > $min) {
+							if ($offsetValue <= $max) {
+								$this->isList = $this->isList->and(TrinaryLogic::createMaybe());
+							} else {
+								$this->isList = TrinaryLogic::createNo();
+							}
 						}
+					} else {
+						$this->isList = TrinaryLogic::createNo();
 					}
-					if ($offsetType->getValue() >= $max) {
+
+					if ($offsetValue >= $max) {
 						/** @var int|float $newAutoIndex */
-						$newAutoIndex = $offsetType->getValue() + 1;
+						$newAutoIndex = $offsetValue + 1;
 						if (is_float($newAutoIndex)) {
 							$newAutoIndex = $max;
 						}

tests/PHPStan/Rules/PhpDoc/VarTagChangedExpressionTypeRuleTest.php

@@ -78,4 +78,26 @@ public function testBug10130(): void
 		]);
 	}
 
+	public function testBug12708(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12708.php'], [
+			[
+				"PHPDoc tag @var with type list<string> is not subtype of native type array{1: 'b', 2: 'c'}.",
+				12,
+			],
+			[
+				"PHPDoc tag @var with type list<string> is not subtype of native type array{0: 'a', 2: 'c'}.",
+				18,
+			],
+			[
+				"PHPDoc tag @var with type list<string> is not subtype of native type array{-1: 'z', 0: 'a', 1: 'b', 2: 'c'}.",
+				24,
+			],
+			[
+				"PHPDoc tag @var with type list<string> is not subtype of native type array{0: 'a', -1: 'z', 1: 'b', 2: 'c'}.",
+				30,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/PhpDoc/data/bug-12708.php

@@ -0,0 +1,31 @@
+<?php declare(strict_types = 1);
+
+function do0()
+{
+	/** @var list<string> */
+	return [0 => 'a', 1 => 'b', 2 => 'c'];
+}
+
+function do1()
+{
+	/** @var list<string> */
+	return [1 => 'b', 2 => 'c'];
+}
+
+function do2()
+{
+	/** @var list<string> */
+	return [0 => 'a', 2 => 'c'];
+}
+
+function do3()
+{
+	/** @var list<string> */
+	return [-1 => 'z', 0 => 'a', 1 => 'b', 2 => 'c'];
+}
+
+function do4()
+{
+	/** @var list<string> */
+	return [0 => 'a', -1 => 'z', 1 => 'b', 2 => 'c'];
+}