From d1597941876588a1f10e10e46785594e5f88786b Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Sun, 27 Jul 2025 00:22:04 +0200
Subject: [PATCH 1/8] Add integration test

---
 .../PHPStan/Levels/LevelsIntegrationTest.php  |  1 +
 .../Levels/data/arrayOffsetAccess-3.json      |  7 ++++
 .../Levels/data/arrayOffsetAccess-4.json      | 37 +++++++++++++++++++
 .../Levels/data/arrayOffsetAccess-6.json      | 12 ++++++
 .../Levels/data/arrayOffsetAccess-7.json      | 12 ++++++
 .../PHPStan/Levels/data/arrayOffsetAccess.php | 24 ++++++++++++
 6 files changed, 93 insertions(+)
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-3.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess.php

diff --git a/tests/PHPStan/Levels/LevelsIntegrationTest.php b/tests/PHPStan/Levels/LevelsIntegrationTest.php
index 12499dce44..044a088f60 100644
--- a/tests/PHPStan/Levels/LevelsIntegrationTest.php
+++ b/tests/PHPStan/Levels/LevelsIntegrationTest.php
@@ -41,6 +41,7 @@ public static function dataTopics(): array
 			['arrayDestructuring'],
 			['listType'],
 			['missingTypes'],
+			['arrayOffsetAccess'],
 		];
 		if (PHP_VERSION_ID >= 80300) {
 			$topics[] = ['constantAccesses83'];
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json
new file mode 100644
index 0000000000..3e23caff09
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Invalid array key type DateTimeImmutable.",
+        "line": 17,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
new file mode 100644
index 0000000000..8ba1c517f1
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
@@ -0,0 +1,37 @@
+[
+    {
+        "message": "Expression \"$a[42]\" on a separate line does not do anything.",
+        "line": 15,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[null]\" on a separate line does not do anything.",
+        "line": 16,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$intOrNull]\" on a separate line does not do anything.",
+        "line": 18,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 19,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 20,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 21,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 22,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
new file mode 100644
index 0000000000..c8bf2976e5
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
@@ -0,0 +1,12 @@
+[
+    {
+        "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $a with no value type specified in iterable type array.",
+        "line": 7,
+        "ignorable": true
+    },
+    {
+        "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $implicitlyMixed with no type specified.",
+        "line": 7,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
new file mode 100644
index 0000000000..2df318590a
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -0,0 +1,12 @@
+[
+    {
+        "message": "Possibly invalid array key type int|object.",
+        "line": 19,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type object|null.",
+        "line": 20,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess.php b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
new file mode 100644
index 0000000000..a0f58dff96
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Levels\ArrayOffsetAccess;
+
+class Foo {
+	/** @return void */
+	public function test(
+		array $a,
+		int|null $intOrNull,
+		object|int $objectOrInt,
+		object|null $objectOrNull,
+		mixed $explicitlyMixed,
+		$implicitlyMixed,
+	) {
+		$a[42];
+		$a[null];
+		$a[new \DateTimeImmutable()];
+		$a[$intOrNull];
+		$a[$objectOrInt];
+		$a[$objectOrNull];
+		$a[$explicitlyMixed];
+		$a[$implicitlyMixed];
+	}
+}

From 23cfa4cc6770cefcf7bd5918914391e6eeff4973 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Sun, 27 Jul 2025 00:53:53 +0200
Subject: [PATCH 2/8] Fix InvalidKeyInArrayDimFetchRule

---
 .../Arrays/InvalidKeyInArrayDimFetchRule.php   | 18 +++++++++++-------
 .../data/arrayOffsetAccess-10-missing.json     |  7 +++++++
 .../Levels/data/arrayOffsetAccess-10.json      |  7 +++++++
 .../Levels/data/arrayOffsetAccess-7.json       |  2 +-
 .../data/arrayOffsetAccess-8-missing.json      |  7 +++++++
 .../Levels/data/arrayOffsetAccess-8.json       |  7 +++++++
 .../data/arrayOffsetAccess-9-missing.json      |  7 +++++++
 .../Levels/data/arrayOffsetAccess-9.json       |  7 +++++++
 8 files changed, 54 insertions(+), 8 deletions(-)
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json
 create mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-9.json

diff --git a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
index 30f7febe49..e90c9bfe9e 100644
--- a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
+++ b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
@@ -10,7 +10,6 @@
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Type\ErrorType;
-use PHPStan\Type\MixedType;
 use PHPStan\Type\Type;
 use PHPStan\Type\VerbosityLevel;
 use function sprintf;
@@ -41,22 +40,27 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
-		$dimensionType = $scope->getType($node->dim);
-		if ($dimensionType instanceof MixedType) {
-			return [];
-		}
-
 		$varType = $this->ruleLevelHelper->findTypeToCheck(
 			$scope,
 			$node->var,
 			'',
-			static fn (Type $varType): bool => $varType->isArray()->no() || AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimensionType)->yes(),
+			static fn (Type $varType): bool => $varType->isArray()->no(),
 		)->getType();
 
 		if ($varType instanceof ErrorType || $varType->isArray()->no()) {
 			return [];
 		}
 
+		$dimensionType = $this->ruleLevelHelper->findTypeToCheck(
+			$scope,
+			$node->dim,
+			'',
+			static fn (Type $dimType): bool => AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimType)->yes(),
+		)->getType();
+		if ($dimensionType instanceof ErrorType) {
+			return [];
+		}
+
 		$isSuperType = AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimensionType);
 		if ($isSuperType->yes() || ($isSuperType->maybe() && !$this->reportMaybes)) {
 			return [];
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
new file mode 100644
index 0000000000..e31aa23936
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Invalid array key type object.",
+        "line": 20,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
new file mode 100644
index 0000000000..80b743c66c
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 22,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
index 2df318590a..b80a88d7c0 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -5,7 +5,7 @@
         "ignorable": true
     },
     {
-        "message": "Possibly invalid array key type object|null.",
+        "message": "Invalid array key type object.",
         "line": 20,
         "ignorable": true
     }
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
new file mode 100644
index 0000000000..e31aa23936
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Invalid array key type object.",
+        "line": 20,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
new file mode 100644
index 0000000000..910aa0e6b1
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Possibly invalid array key type object|null.",
+        "line": 20,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json
new file mode 100644
index 0000000000..e31aa23936
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Invalid array key type object.",
+        "line": 20,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
new file mode 100644
index 0000000000..50cc3c7bbb
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 21,
+        "ignorable": true
+    }
+]
\ No newline at end of file

From 90ef5c45c549d1a3c450086faea9242c4ee27f09 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Sun, 27 Jul 2025 01:06:10 +0200
Subject: [PATCH 3/8] Fix RuleLevelHelper

---
 src/Rules/RuleLevelHelper.php                              | 6 +++++-
 .../PHPStan/Levels/data/arrayOffsetAccess-10-missing.json  | 7 -------
 tests/PHPStan/Levels/data/arrayOffsetAccess-6.json         | 2 +-
 tests/PHPStan/Levels/data/arrayOffsetAccess-7.json         | 2 +-
 tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json | 7 -------
 tests/PHPStan/Levels/data/arrayOffsetAccess-8.json         | 7 -------
 tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json | 7 -------
 7 files changed, 7 insertions(+), 31 deletions(-)
 delete mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
 delete mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
 delete mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
 delete mode 100644 tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json

diff --git a/src/Rules/RuleLevelHelper.php b/src/Rules/RuleLevelHelper.php
index 109b30a2b3..d82ff0745b 100644
--- a/src/Rules/RuleLevelHelper.php
+++ b/src/Rules/RuleLevelHelper.php
@@ -190,7 +190,11 @@ private function findTypeToCheckImplementation(
 		bool $isTopLevel = false,
 	): FoundTypeResult
 	{
-		if (!$this->checkNullables && !$type->isNull()->yes()) {
+		if (
+			!$this->checkNullables
+			&& !$type->isNull()->yes()
+			&& !$unionTypeCriteriaCallback(new NullType())
+		) {
 			$type = TypeCombinator::removeNull($type);
 		}
 
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
deleted file mode 100644
index e31aa23936..0000000000
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-10-missing.json
+++ /dev/null
@@ -1,7 +0,0 @@
-[
-    {
-        "message": "Invalid array key type object.",
-        "line": 20,
-        "ignorable": true
-    }
-]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
index c8bf2976e5..0033cdbfde 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
@@ -9,4 +9,4 @@
         "line": 7,
         "ignorable": true
     }
-]
\ No newline at end of file
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
index b80a88d7c0..2df318590a 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -5,7 +5,7 @@
         "ignorable": true
     },
     {
-        "message": "Invalid array key type object.",
+        "message": "Possibly invalid array key type object|null.",
         "line": 20,
         "ignorable": true
     }
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
deleted file mode 100644
index e31aa23936..0000000000
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-8-missing.json
+++ /dev/null
@@ -1,7 +0,0 @@
-[
-    {
-        "message": "Invalid array key type object.",
-        "line": 20,
-        "ignorable": true
-    }
-]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
deleted file mode 100644
index 910aa0e6b1..0000000000
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-8.json
+++ /dev/null
@@ -1,7 +0,0 @@
-[
-    {
-        "message": "Possibly invalid array key type object|null.",
-        "line": 20,
-        "ignorable": true
-    }
-]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json
deleted file mode 100644
index e31aa23936..0000000000
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-9-missing.json
+++ /dev/null
@@ -1,7 +0,0 @@
-[
-    {
-        "message": "Invalid array key type object.",
-        "line": 20,
-        "ignorable": true
-    }
-]
\ No newline at end of file

From bc59757c1aeb9741c201ba0c91361bd730f075d4 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Sun, 27 Jul 2025 01:18:50 +0200
Subject: [PATCH 4/8] Fix lint

---
 .../Levels/data/arrayOffsetAccess-6.json       |  4 ++--
 .../PHPStan/Levels/data/arrayOffsetAccess.php  | 18 +++++++++---------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
index 0033cdbfde..1e3cefa62e 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
@@ -1,12 +1,12 @@
 [
     {
         "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $a with no value type specified in iterable type array.",
-        "line": 7,
+        "line": 13,
         "ignorable": true
     },
     {
         "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $implicitlyMixed with no type specified.",
-        "line": 7,
+        "line": 13,
         "ignorable": true
     }
 ]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess.php b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
index a0f58dff96..cff9bd9041 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess.php
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
@@ -3,15 +3,15 @@
 namespace Levels\ArrayOffsetAccess;
 
 class Foo {
-	/** @return void */
-	public function test(
-		array $a,
-		int|null $intOrNull,
-		object|int $objectOrInt,
-		object|null $objectOrNull,
-		mixed $explicitlyMixed,
-		$implicitlyMixed,
-	) {
+	/**
+	 * @param int|null $intOrNull
+	 * @param object|int $objectOrInt
+	 * @param object|null $objectOrNull
+	 * @param mixed $explicitlyMixed
+	 * @return void
+	 */
+	public function test(array $a, $intOrNull, $objectOrInt, $objectOrNull, $explicitlyMixed, $implicitlyMixed)
+	{
 		$a[42];
 		$a[null];
 		$a[new \DateTimeImmutable()];

From 6f99f04c397e57edd81fcfc811a43aced9eac317 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Tue, 2 Sep 2025 17:15:22 +0200
Subject: [PATCH 5/8] Add more cases

---
 .../Levels/data/arrayOffsetAccess-4.json      | 107 +++++++++++++++++-
 .../Levels/data/arrayOffsetAccess-6.json      |  10 ++
 .../Levels/data/arrayOffsetAccess-7.json      |  17 ++-
 .../PHPStan/Levels/data/arrayOffsetAccess.php |  31 ++++-
 4 files changed, 161 insertions(+), 4 deletions(-)

diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
index 8ba1c517f1..3f91016ab3 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
@@ -33,5 +33,110 @@
         "message": "Expression \"$a[$implicitlyMixed]\" on a separate line does not do anything.",
         "line": 22,
         "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[42]\" on a separate line does not do anything.",
+        "line": 24,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[null]\" on a separate line does not do anything.",
+        "line": 25,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$intOrNull]\" on a separate line does not do anything.",
+        "line": 27,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 28,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 29,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 30,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 31,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[42]\" on a separate line does not do anything.",
+        "line": 33,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[null]\" on a separate line does not do anything.",
+        "line": 34,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$intOrNull]\" on a separate line does not do anything.",
+        "line": 36,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 37,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 38,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 39,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 40,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[42]\" on a separate line does not do anything.",
+        "line": 42,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[null]\" on a separate line does not do anything.",
+        "line": 43,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$intOrNull]\" on a separate line does not do anything.",
+        "line": 45,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 46,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 47,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 48,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 49,
+        "ignorable": true
     }
-]
\ No newline at end of file
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
index 1e3cefa62e..5c3bc3d299 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
@@ -4,6 +4,16 @@
         "line": 13,
         "ignorable": true
     },
+    {
+      "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $arrayOrObject with generic interface ArrayAccess but does not specify its types: TKey, TValue",
+        "line": 13,
+        "ignorable": true
+    },
+    {
+      "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $arrayOrObject with no value type specified in iterable type array.",
+        "line": 13,
+        "ignorable": true
+    },
     {
         "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $implicitlyMixed with no type specified.",
         "line": 13,
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
index 2df318590a..072b72e8cf 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -8,5 +8,20 @@
         "message": "Possibly invalid array key type object|null.",
         "line": 20,
         "ignorable": true
+    },
+    {
+        "message": "Invalid array key type DateTimeImmutable.",
+        "line": 26,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type int|object.",
+        "line": 28,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type object|null.",
+        "line": 29,
+        "ignorable": true
     }
-]
\ No newline at end of file
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess.php b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
index cff9bd9041..362bb5c03f 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess.php
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
@@ -4,13 +4,13 @@
 
 class Foo {
 	/**
+	 * @param array|\ArrayAccess $arrayOrObject
 	 * @param int|null $intOrNull
 	 * @param object|int $objectOrInt
 	 * @param object|null $objectOrNull
 	 * @param mixed $explicitlyMixed
-	 * @return void
 	 */
-	public function test(array $a, $intOrNull, $objectOrInt, $objectOrNull, $explicitlyMixed, $implicitlyMixed)
+	public function test(array $a, $arrayOrObject, $intOrNull, $objectOrInt, $objectOrNull, $explicitlyMixed, $implicitlyMixed): void
 	{
 		$a[42];
 		$a[null];
@@ -20,5 +20,32 @@ public function test(array $a, $intOrNull, $objectOrInt, $objectOrNull, $explici
 		$a[$objectOrNull];
 		$a[$explicitlyMixed];
 		$a[$implicitlyMixed];
+
+		$arrayOrObject[42];
+		$arrayOrObject[null];
+		$arrayOrObject[new \DateTimeImmutable()];
+		$arrayOrObject[$intOrNull];
+		$arrayOrObject[$objectOrInt];
+		$arrayOrObject[$objectOrNull];
+		$arrayOrObject[$explicitlyMixed];
+		$arrayOrObject[$implicitlyMixed];
+
+		$explicitlyMixed[42];
+		$explicitlyMixed[null];
+		$explicitlyMixed[new \DateTimeImmutable()];
+		$explicitlyMixed[$intOrNull];
+		$explicitlyMixed[$objectOrInt];
+		$explicitlyMixed[$objectOrNull];
+		$explicitlyMixed[$explicitlyMixed];
+		$explicitlyMixed[$implicitlyMixed];
+
+		$implicitlyMixed[42];
+		$implicitlyMixed[null];
+		$implicitlyMixed[new \DateTimeImmutable()];
+		$implicitlyMixed[$intOrNull];
+		$implicitlyMixed[$objectOrInt];
+		$implicitlyMixed[$objectOrNull];
+		$implicitlyMixed[$explicitlyMixed];
+		$implicitlyMixed[$implicitlyMixed];
 	}
 }

From 7e0f73b1e2b4001c649550e64662df6a9a26f5e8 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Tue, 2 Sep 2025 17:48:31 +0200
Subject: [PATCH 6/8] Improve

---
 src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php | 13 +++++++++++--
 tests/PHPStan/Levels/data/arrayOffsetAccess-7.json |  2 +-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
index e90c9bfe9e..5ba1a88009 100644
--- a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
+++ b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
@@ -47,7 +47,12 @@ public function processNode(Node $node, Scope $scope): array
 			static fn (Type $varType): bool => $varType->isArray()->no(),
 		)->getType();
 
-		if ($varType instanceof ErrorType || $varType->isArray()->no()) {
+		if ($varType instanceof ErrorType) {
+			return [];
+		}
+
+		$isArray = $varType->isArray();
+		if ($isArray->no() || ($isArray->maybe() && !$this->reportMaybes)) {
 			return [];
 		}
 
@@ -68,7 +73,11 @@ public function processNode(Node $node, Scope $scope): array
 
 		return [
 			RuleErrorBuilder::message(
-				sprintf('%s array key type %s.', $isSuperType->no() ? 'Invalid' : 'Possibly invalid', $dimensionType->describe(VerbosityLevel::typeOnly())),
+				sprintf(
+					'%s array key type %s.',
+					$isArray->yes() && $isSuperType->no() ? 'Invalid' : 'Possibly invalid',
+					$dimensionType->describe(VerbosityLevel::typeOnly()),
+				),
 			)->identifier('offsetAccess.invalidOffset')->build(),
 		];
 	}
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
index 072b72e8cf..674057be06 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -10,7 +10,7 @@
         "ignorable": true
     },
     {
-        "message": "Invalid array key type DateTimeImmutable.",
+        "message": "Possibly invalid array key type DateTimeImmutable.",
         "line": 26,
         "ignorable": true
     },

From 03b04f54470da0776a330b0df69fff6f9642503a Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Tue, 2 Sep 2025 17:58:59 +0200
Subject: [PATCH 7/8] Fix level 9

---
 .../Levels/data/arrayOffsetAccess-9.json      | 47 ++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
index 50cc3c7bbb..edca311940 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
@@ -3,5 +3,50 @@
         "message": "Possibly invalid array key type mixed.",
         "line": 21,
         "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 30,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset 42 on mixed.",
+        "line": 33,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset null on mixed.",
+        "line": 34,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset DateTimeImmutable on mixed.",
+        "line": 35,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|null on mixed.",
+        "line": 36,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|object on mixed.",
+        "line": 37,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset object|null on mixed.",
+        "line": 38,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 39,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 40,
+        "ignorable": true
     }
-]
\ No newline at end of file
+]

From 9628a156de2d047409f061fc344c63ea11c54835 Mon Sep 17 00:00:00 2001
From: Vincent Langlet <vincentlanglet@hotmail.fr>
Date: Tue, 2 Sep 2025 18:05:17 +0200
Subject: [PATCH 8/8] Fix level 10

---
 .../Levels/data/arrayOffsetAccess-10.json     | 47 ++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
index 80b743c66c..e0b5d1d2d8 100644
--- a/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
@@ -3,5 +3,50 @@
         "message": "Possibly invalid array key type mixed.",
         "line": 22,
         "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 31,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset 42 on mixed.",
+        "line": 42,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset null on mixed.",
+        "line": 43,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset DateTimeImmutable on mixed.",
+        "line": 44,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|null on mixed.",
+        "line": 45,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|object on mixed.",
+        "line": 46,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset object|null on mixed.",
+        "line": 47,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 48,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 49,
+        "ignorable": true
     }
-]
\ No newline at end of file
+]