From 3afcdd8cf1c19287bf8f0bbd751ed11ef8287b38 Mon Sep 17 00:00:00 2001
From: phpstan-bot <79867460+phpstan-bot@users.noreply.github.com>
Date: Mon, 16 Feb 2026 23:40:02 +0000
Subject: [PATCH 1/2] Fix false positive when setting optional array offset on
 template constant array property

- Override setOffsetValueType() and setExistingOffsetValueType() in TemplateConstantArrayType
- When the offset exists in the template's bound and the value type is accepted by the bound's value type, return the template type itself
- This preserves the template contract: modifying an in-bound offset on a template value still produces a valid template value
- New regression test in tests/PHPStan/Rules/Properties/data/bug-7170.php

Closes https://github.com/phpstan/phpstan/issues/7170
---
 .../Generic/TemplateConstantArrayType.php     | 38 ++++++++++++++++
 .../TypesAssignedToPropertiesRuleTest.php     |  5 +++
 .../Rules/Properties/data/bug-7170.php        | 44 +++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 tests/PHPStan/Rules/Properties/data/bug-7170.php

diff --git a/src/Type/Generic/TemplateConstantArrayType.php b/src/Type/Generic/TemplateConstantArrayType.php
index fbc13bad6d..9ea9cee28f 100644
--- a/src/Type/Generic/TemplateConstantArrayType.php
+++ b/src/Type/Generic/TemplateConstantArrayType.php
@@ -35,4 +35,42 @@ public function __construct(
 		$this->default = $default;
 	}
 
+	public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $unionValues = true): Type
+	{
+		if ($this->isOffsetWithinBound($offsetType, $valueType)) {
+			return $this;
+		}
+
+		return parent::setOffsetValueType($offsetType, $valueType, $unionValues);
+	}
+
+	public function setExistingOffsetValueType(Type $offsetType, Type $valueType): Type
+	{
+		if ($this->isOffsetWithinBound($offsetType, $valueType)) {
+			return $this;
+		}
+
+		return parent::setExistingOffsetValueType($offsetType, $valueType);
+	}
+
+	private function isOffsetWithinBound(?Type $offsetType, Type $valueType): bool
+	{
+		if ($offsetType === null) {
+			return false;
+		}
+
+		$boundKeyTypes = $this->bound->getKeyTypes();
+		$boundValueTypes = $this->bound->getValueTypes();
+
+		foreach ($boundKeyTypes as $i => $boundKeyType) {
+			if (!$offsetType->equals($boundKeyType)) {
+				continue;
+			}
+
+			return $boundValueTypes[$i]->accepts($valueType, true)->yes();
+		}
+
+		return false;
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php b/tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php
index 29c2c32aca..a159d25d46 100644
--- a/tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php
+++ b/tests/PHPStan/Rules/Properties/TypesAssignedToPropertiesRuleTest.php
@@ -1003,4 +1003,9 @@ public function testCloneWith(): void
 		]);
 	}
 
+	public function testBug7170(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-7170.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/data/bug-7170.php b/tests/PHPStan/Rules/Properties/data/bug-7170.php
new file mode 100644
index 0000000000..1d5ff5d05b
--- /dev/null
+++ b/tests/PHPStan/Rules/Properties/data/bug-7170.php
@@ -0,0 +1,44 @@
+<?php declare(strict_types = 1);
+
+namespace Bug7170;
+
+/**
+ * @template Tdata of array{extension?: array<mixed>}
+ */
+class Data
+{
+	/**
+	 * @var Tdata
+	 */
+	private $data;
+
+	/**
+	 * @param Tdata $data
+	 */
+	public function __construct(array $data = [])
+	{
+		$this->data = $data;
+	}
+
+	public function setExtensionProperty(): void
+	{
+		if (!isset($this->data['extension'])) {
+			$this->data['extension'] = [];
+		}
+	}
+}
+
+class NonGeneric
+{
+	/**
+	 * @var array{extension?: array<mixed>}
+	 */
+	private $data;
+
+	public function setData(): void
+	{
+		if (!isset($this->data['extension'])) {
+			$this->data['extension'] = [];
+		}
+	}
+}

From a14e9628d3b12a5c4301a1759dda302c6d89f280 Mon Sep 17 00:00:00 2001
From: phpstan-bot <ondrej+phpstanbot@mirtes.cz>
Date: Mon, 16 Feb 2026 23:47:08 +0000
Subject: [PATCH 2/2] Add regression test for #10172

Closes https://github.com/phpstan/phpstan/issues/10172
---
 .../Rules/Methods/ReturnTypeRuleTest.php      |  5 +++++
 .../PHPStan/Rules/Methods/data/bug-10172.php  | 21 +++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 tests/PHPStan/Rules/Methods/data/bug-10172.php

diff --git a/tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php b/tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php
index 84e81f0f33..40f4e46571 100644
--- a/tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php
@@ -1310,4 +1310,9 @@ public function testBug9669(): void
 		$this->analyse([__DIR__ . '/data/bug-9669.php'], []);
 	}
 
+	public function testBug10172(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-10172.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Methods/data/bug-10172.php b/tests/PHPStan/Rules/Methods/data/bug-10172.php
new file mode 100644
index 0000000000..434ac1ae39
--- /dev/null
+++ b/tests/PHPStan/Rules/Methods/data/bug-10172.php
@@ -0,0 +1,21 @@
+<?php declare(strict_types = 1);
+
+namespace Bug10172;
+
+class HelloWorld
+{
+    /**
+     * @template T of array{data: array<mixed>}
+     *
+     * @param T $a
+     *
+     * @return T
+     */
+    public function foo(array $a): array
+    {
+        foreach ($a['data'] as $i) {
+        }
+
+        return $a;
+    }
+}