ArrayType - setting new offset with [] on array with constant-integer offset will add one to the offset

Author: ondrejmirtes

src/Type/ArrayType.php

@@ -455,7 +455,17 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $uni
 			if ($isKeyTypeInteger->no()) {
 				$offsetType = new IntegerType();
 			} elseif ($isKeyTypeInteger->yes()) {
-				$offsetType = $this->keyType;
+				/** @var list<ConstantIntegerType> $constantScalars */
+				$constantScalars = $this->keyType->getConstantScalarTypes();
+				if (count($constantScalars) > 0) {
+					foreach ($constantScalars as $constantScalar) {
+						$constantScalars[] = ConstantTypeHelper::getTypeFromValue($constantScalar->getValue() + 1);
+					}
+
+					$offsetType = TypeCombinator::union(...$constantScalars);
+				} else {
+					$offsetType = $this->keyType;
+				}
 			} else {
 				$integerTypes = [];
 				TypeTraverser::map($this->keyType, static function (Type $type, callable $traverse) use (&$integerTypes): Type {

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -483,4 +483,12 @@ public function testBug10064(): void
 		$this->analyse([__DIR__ . '/data/bug-10064.php'], []);
 	}
 
+	public function testBug9328(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->strictUnnecessaryNullsafePropertyFetch = true;
+
+		$this->analyse([__DIR__ . '/data/bug-9328.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Variables/data/bug-9328.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Bug9328;
+
+function (): void {
+	$contents = file('foo.ini', FILE_IGNORE_NEW_LINES);
+	if (false === $contents) {
+		throw new \Exception('Failed to read file');
+	}
+	// Add section so that the last one is flushed:
+	$contents[] = '[--]';
+	$currentSection = '';
+	$sections = [];
+	$lines = [];
+	foreach ($contents as $line) {
+		if (
+			str_starts_with($line, '[')
+			&& str_ends_with($line, ']')
+			&& strlen($line) > 2
+		) {
+			// flush previously collected section:
+			if ($lines) {
+				$sections[] = [
+					'name' => $currentSection,
+					'lines' => $lines,
+				];
+			}
+			$currentSection = substr($line, 1, -1);
+			$lines = [];
+		}
+		$lines[] = $line;
+	}
+
+	if (isset($sections[1])) {
+		echo "We have multiple remaining sections!\n";
+	}
+};