Fix false positive with reportPossiblyNonexistentConstantArrayOffset: true

Author: ondrejmirtes

src/Type/Constant/ConstantArrayType.php

@@ -618,6 +618,17 @@ public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 
 			return TrinaryLogic::extremeIdentity(...$results);
 		}
+		if ($offsetType instanceof IntegerRangeType) {
+			$finiteTypes = $offsetType->getFiniteTypes();
+			if ($finiteTypes !== []) {
+				$results = [];
+				foreach ($finiteTypes as $innerType) {
+					$results[] = $this->hasOffsetValueType($innerType);
+				}
+
+				return TrinaryLogic::extremeIdentity(...$results);
+			}
+		}
 
 		$result = TrinaryLogic::createNo();
 		foreach ($this->keyTypes as $i => $keyType) {

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -853,4 +853,15 @@ public function testReportPossiblyNonexistentArrayOffset(bool $reportPossiblyNon
 		$this->analyse([__DIR__ . '/data/report-possibly-nonexistent-array-offset.php'], $errors);
 	}
 
+	public function testBug10997(): void
+	{
+		$this->reportPossiblyNonexistentConstantArrayOffset = true;
+		$this->analyse([__DIR__ . '/data/bug-10997.php'], [
+			[
+				'Offset int<0, 4> might not exist on array{1, 2, 3, 4}.',
+				15,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Arrays/data/bug-10997.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Bug10997;
+
+function (): void {
+	$array = [1, 2, 3, 4];
+	for ($i = 0; $i < count($array); ++$i) {
+		echo $array[$i], "\n";
+	}
+};
+
+function (): void {
+	$array = [1, 2, 3, 4];
+	for ($i = 0; $i < 5; ++$i) {
+		echo $array[$i], "\n";
+	}
+};