From 69986aa2e54ca207a58a70c8ccdaff917def0c7c Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Mon, 9 Mar 2026 17:22:07 +0000
Subject: [PATCH] Fix false positive for numeric string offset on string-keyed
 array in isset()

- In ArrayType::hasOffsetValueType and getOffsetValueType, toArrayKey() converts
  numeric strings like '1234' to integers, losing the original string type info
- Added check against original offset type before toArrayKey() conversion so that
  a string offset on a string-keyed array is not incorrectly rejected
- Updated NonexistentOffsetInArrayDimFetchRuleTest to reflect that '0' on
  array<string, string> is no longer a false positive
- New regression test in tests/PHPStan/Rules/Variables/data/bug-4296.php

Closes https://github.com/phpstan/phpstan/issues/4296
---
 src/Type/ArrayType.php                        |  4 +++
 ...nexistentOffsetInArrayDimFetchRuleTest.php |  4 ---
 .../PHPStan/Rules/Variables/IssetRuleTest.php |  7 +++++
 .../PHPStan/Rules/Variables/data/bug-4296.php | 30 +++++++++++++++++++
 4 files changed, 41 insertions(+), 4 deletions(-)
 create mode 100644 tests/PHPStan/Rules/Variables/data/bug-4296.php

diff --git a/src/Type/ArrayType.php b/src/Type/ArrayType.php
index 288caefdc6..5754709130 100644
--- a/src/Type/ArrayType.php
+++ b/src/Type/ArrayType.php
@@ -268,6 +268,7 @@ public function looseCompare(Type $type, PhpVersion $phpVersion): BooleanType
 
 	public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 	{
+		$originalOffsetType = $offsetType;
 		$offsetArrayKeyType = $offsetType->toArrayKey();
 		if ($offsetArrayKeyType instanceof ErrorType) {
 			$allowedArrayKeys = AllowedArrayKeysTypes::getType();
@@ -279,6 +280,7 @@ public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 		$offsetType = $offsetArrayKeyType;
 
 		if ($this->getKeyType()->isSuperTypeOf($offsetType)->no()
+			&& $this->getKeyType()->isSuperTypeOf($originalOffsetType)->no()
 			&& ($offsetType->isString()->no() || !$offsetType->isConstantScalarValue()->no())
 		) {
 			return TrinaryLogic::createNo();
@@ -289,8 +291,10 @@ public function hasOffsetValueType(Type $offsetType): TrinaryLogic
 
 	public function getOffsetValueType(Type $offsetType): Type
 	{
+		$originalOffsetType = $offsetType;
 		$offsetType = $offsetType->toArrayKey();
 		if ($this->getKeyType()->isSuperTypeOf($offsetType)->no()
+			&& $this->getKeyType()->isSuperTypeOf($originalOffsetType)->no()
 			&& ($offsetType->isString()->no() || !$offsetType->isConstantScalarValue()->no())
 		) {
 			return new ErrorType();
diff --git a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
index c066553f27..91d3d7ef02 100644
--- a/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php
@@ -63,10 +63,6 @@ public function testRule(): void
 				'Offset 0 does not exist on array<string, string>.',
 				111,
 			],
-			[
-				'Offset \'0\' does not exist on array<string, string>.',
-				112,
-			],
 			[
 				'Offset int does not exist on array<string, string>.',
 				114,
diff --git a/tests/PHPStan/Rules/Variables/IssetRuleTest.php b/tests/PHPStan/Rules/Variables/IssetRuleTest.php
index 045af8b58b..85dc192667 100644
--- a/tests/PHPStan/Rules/Variables/IssetRuleTest.php
+++ b/tests/PHPStan/Rules/Variables/IssetRuleTest.php
@@ -513,4 +513,11 @@ public function testBug9503(): void
 		$this->analyse([__DIR__ . '/data/bug-9503.php'], []);
 	}
 
+	public function testBug4296(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/data/bug-4296.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Variables/data/bug-4296.php b/tests/PHPStan/Rules/Variables/data/bug-4296.php
new file mode 100644
index 0000000000..dd81534e3a
--- /dev/null
+++ b/tests/PHPStan/Rules/Variables/data/bug-4296.php
@@ -0,0 +1,30 @@
+<?php declare(strict_types = 1);
+
+namespace Bug4296;
+
+class Test {
+	private string $id;
+
+	public function __construct(string $id)
+	{
+		$this->id = $id;
+	}
+
+	public function getId(): string
+	{
+		return $this->id;
+	}
+}
+
+function (): void {
+	$map = [];
+	foreach ([new Test('1234')] as $test) {
+		$map[$test->getId()] = $test;
+	}
+
+	foreach (['1234'] as $value) {
+		if (isset($map[$value])) {
+			$found = 1;
+		}
+	}
+};