From 2e9c7638590a09e1a5dd80ee8fc35f0e28b6059f Mon Sep 17 00:00:00 2001
From: USAMI Kenta <tadsan@zonu.me>
Date: Sat, 3 Oct 2026 22:35:12 +0900
Subject: [PATCH 1/2] Report impure methods overriding
 @pure-unless-parameter-passed methods

---
 src/Rules/Methods/MethodSignatureRule.php     | 12 ++++
 .../Rules/Methods/MethodSignatureRuleTest.php | 13 +++++
 ...signature-pure-unless-parameter-passed.php | 55 +++++++++++++++++++
 3 files changed, 80 insertions(+)
 create mode 100644 tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php

diff --git a/src/Rules/Methods/MethodSignatureRule.php b/src/Rules/Methods/MethodSignatureRule.php
index 4f410a7b321..5d0cafb6024 100644
--- a/src/Rules/Methods/MethodSignatureRule.php
+++ b/src/Rules/Methods/MethodSignatureRule.php
@@ -94,6 +94,18 @@ public function processNode(Node $node, Scope $scope): array
 					$parentMethodDeclaringClass->getDisplayName(),
 					$parentMethod->getName(),
 				))->identifier('method.impureOverridePureUnlessCallable')->build();
+			} elseif (
+				$this->reportMethodPurityOverride
+				&& $method->isPure()->no()
+				&& count($parentMethod->getPureUnlessParameterPassedParameters()) > 0
+			) {
+				$errors[] = RuleErrorBuilder::message(sprintf(
+					'Impure method %s::%s() overrides method %s::%s() marked @pure-unless-parameter-passed.',
+					$method->getDeclaringClass()->getDisplayName(),
+					$method->getName(),
+					$parentMethodDeclaringClass->getDisplayName(),
+					$parentMethod->getName(),
+				))->identifier('method.impureOverridePureUnlessParameterPassed')->build();
 			}
 
 			$parentVariants = $parentMethod->getVariants();
diff --git a/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php b/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
index 109b85fd3c9..403abab8187 100644
--- a/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
@@ -659,4 +659,17 @@ public function testPureUnlessCallableIsImpureOverride(): void
 		]);
 	}
 
+	public function testPureUnlessParameterPassedOverride(): void
+	{
+		$this->reportMaybes = true;
+		$this->reportStatic = true;
+		$this->reportMethodPurityOverride = true;
+		$this->analyse([__DIR__ . '/data/method-signature-pure-unless-parameter-passed.php'], [
+			[
+				'Impure method MethodSignaturePureUnlessParameterPassed\ImpureChild::replace() overrides method MethodSignaturePureUnlessParameterPassed\PureUnlessParent::replace() marked @pure-unless-parameter-passed.',
+				22,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php b/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php
new file mode 100644
index 00000000000..4a0d1cd2457
--- /dev/null
+++ b/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php
@@ -0,0 +1,55 @@
+<?php declare(strict_types = 1);
+
+namespace MethodSignaturePureUnlessParameterPassed;
+
+interface PureUnlessParent
+{
+
+	/**
+	 * @param-out int $count
+	 * @pure-unless-parameter-passed $count
+	 */
+	public function replace(string $subject, int &$count = 0): string;
+
+}
+
+class ImpureChild implements PureUnlessParent
+{
+
+	/**
+	 * @phpstan-impure
+	 */
+	public function replace(string $subject, int &$count = 0): string
+	{
+		echo 'side effect';
+		$count = 1;
+
+		return $subject;
+	}
+
+}
+
+class InheritingChild implements PureUnlessParent
+{
+
+	public function replace(string $subject, int &$count = 0): string
+	{
+		$count = 1;
+
+		return $subject;
+	}
+
+}
+
+class PureChild implements PureUnlessParent
+{
+
+	/**
+	 * @phpstan-pure
+	 */
+	public function replace(string $subject, int &$count = 0): string
+	{
+		return $subject;
+	}
+
+}

From 6fa0be66720a5ed845d1f888a0add1cbc7fc6046 Mon Sep 17 00:00:00 2001
From: USAMI Kenta <tadsan@zonu.me>
Date: Sun, 4 Oct 2026 02:42:32 +0900
Subject: [PATCH 2/2] Cover class-level purity tags on overrides of
 @pure-unless-parameter-passed methods

---
 .../Rules/Methods/MethodSignatureRuleTest.php |  4 +++
 ...signature-pure-unless-parameter-passed.php | 29 +++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php b/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
index 403abab8187..f24317d6b61 100644
--- a/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/MethodSignatureRuleTest.php
@@ -669,6 +669,10 @@ public function testPureUnlessParameterPassedOverride(): void
 				'Impure method MethodSignaturePureUnlessParameterPassed\ImpureChild::replace() overrides method MethodSignaturePureUnlessParameterPassed\PureUnlessParent::replace() marked @pure-unless-parameter-passed.',
 				22,
 			],
+			[
+				'Impure method MethodSignaturePureUnlessParameterPassed\AllMethodsImpureChild::replace() overrides method MethodSignaturePureUnlessParameterPassed\PureUnlessParent::replace() marked @pure-unless-parameter-passed.',
+				76,
+			],
 		]);
 	}
 
diff --git a/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php b/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php
index 4a0d1cd2457..600a91a91b9 100644
--- a/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php
+++ b/tests/PHPStan/Rules/Methods/data/method-signature-pure-unless-parameter-passed.php
@@ -53,3 +53,32 @@ public function replace(string $subject, int &$count = 0): string
 	}
 
 }
+
+/**
+ * @phpstan-all-methods-pure
+ */
+class AllMethodsPureChild implements PureUnlessParent
+{
+
+	public function replace(string $subject, int &$count = 0): string
+	{
+		return $subject;
+	}
+
+}
+
+/**
+ * @phpstan-all-methods-impure
+ */
+class AllMethodsImpureChild implements PureUnlessParent
+{
+
+	public function replace(string $subject, int &$count = 0): string
+	{
+		echo 'side effect';
+		$count = 1;
+
+		return $subject;
+	}
+
+}