From 03ab0d0e3c161af94ee03c05266d2e2302601e2e Mon Sep 17 00:00:00 2001
From: HawkForge <75696486+HawkForge@users.noreply.github.com>
Date: Thu, 15 Oct 2026 16:23:23 +0600
Subject: [PATCH] Ignore a lower bound that refers to the inferred template
 argument itself

`$map = new WeakAnalysingMap(); $map->set($map);` with
`@param TOwner $owner` puts `WeakAnalysingMap<TOwner>` as a lower bound
on the `new` site's own `TOwner`. Resolving it substituted the site's
default for the inner `TOwner`, so `$map` became
`WeakAnalysingMap<WeakAnalysingMap<object>>` - and then no longer
matched the parameter it was inferred from.

A bound that contains the argument it bounds says nothing about it.
Skip it, so the argument falls back to what 2.2 inferred.

Closes https://github.com/phpstan/phpstan/issues/15434
---
 .../Generics/TemplateArgumentSolver.php       | 19 +++++++++++++++
 .../Rules/Methods/CallMethodsRuleTest.php     |  8 +++++++
 .../PHPStan/Rules/Methods/data/bug-15434.php  | 23 +++++++++++++++++++
 3 files changed, 50 insertions(+)
 create mode 100644 tests/PHPStan/Rules/Methods/data/bug-15434.php

diff --git a/src/Analyser/Generics/TemplateArgumentSolver.php b/src/Analyser/Generics/TemplateArgumentSolver.php
index 25fcb53900b..310d7d426c6 100644
--- a/src/Analyser/Generics/TemplateArgumentSolver.php
+++ b/src/Analyser/Generics/TemplateArgumentSolver.php
@@ -131,6 +131,18 @@ private function removeSelfBounds(Type $type, string $key): Type
 		return $type;
 	}
 
+	private function refersToKey(Type $type, string $key): bool
+	{
+		$refers = false;
+		TypeTraverser::map($type, function (Type $type, callable $traverse) use ($key, &$refers): Type {
+			if ($type instanceof UnresolvedTemplateArgumentType && $this->representative(self::key($type->getSite(), $type->getTemplateName())) === $key) {
+				$refers = true;
+			}
+			return $refers ? $type : $traverse($type);
+		});
+		return $refers;
+	}
+
 	/** @var array<string, true> */
 	private array $resolving = [];
 
@@ -207,7 +219,14 @@ private function resolveObservation(array $observation): Type
 		$initial = $observation['initial'] !== null ? $this->substituteResolutions($observation['initial']) : null;
 		$template = $observation['marker']->getTemplate();
 		$lowerBounds = [];
+		$key = $this->representative(self::key($observation['marker']->getSite(), $observation['marker']->getTemplateName()));
 		foreach ($observation['lowerBounds'] as $lowerBound) {
+			if ($this->refersToKey($lowerBound, $key)) {
+				// the object passed to its own method ($map->set($map) with
+				// set(TOwner $owner)) can only be bounded by itself - it says
+				// nothing about the argument
+				continue;
+			}
 			$inferred = $template->inferTemplateTypes($this->substituteResolutions($lowerBound))->getType($template->getName());
 			if ($inferred === null) {
 				continue;
diff --git a/tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php b/tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php
index e03a97fc739..25765ed7ee4 100644
--- a/tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php
@@ -4560,6 +4560,14 @@ public function testBug15251(): void
 		$this->analyse([__DIR__ . '/data/bug-15251.php'], []);
 	}
 
+	public function testBug15434(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkNullables = true;
+		$this->checkUnionTypes = true;
+		$this->analyse([__DIR__ . '/data/bug-15434.php'], []);
+	}
+
 	#[RequiresPhp('>= 8.1.0')]
 	public function testClassConstantWildcardArguments(): void
 	{
diff --git a/tests/PHPStan/Rules/Methods/data/bug-15434.php b/tests/PHPStan/Rules/Methods/data/bug-15434.php
new file mode 100644
index 00000000000..1aa4d33de20
--- /dev/null
+++ b/tests/PHPStan/Rules/Methods/data/bug-15434.php
@@ -0,0 +1,23 @@
+<?php declare(strict_types = 1);
+
+namespace Bug15434;
+
+class Test
+{
+    public function testSet(): void
+    {
+        $map = new WeakAnalysingMap();
+        $map->set($map);
+	}
+}
+
+/**
+ * @template TOwner of object
+ */
+class WeakAnalysingMap
+{
+    /**
+     * @param TOwner $owner
+     */
+    public function set(object $owner): void {}
+}
\ No newline at end of file