Address review: add rule test and post-chain type assertions for bug-6934

- Add CallMethodsRule test to verify no parameter type error on
  $node?->parentNode?->removeChild($node)
- Assert $node remains DOMNode|null after the nullsafe chain
- Assert $foo remains Foo|null after the nullsafe chain

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-6934.php

@@ -9,6 +9,7 @@
 
 function removeFromParent(?DOMNode $node): void {
 	$node?->parentNode?->removeChild($node);
+	assertType('DOMNode|null', $node);
 }
 
 function testNarrowing(?DOMNode $node): void {
@@ -23,4 +24,5 @@ public function doSomething(): string {
 
 function testNullsafeChainArgs(?Foo $foo): void {
 	$foo?->doSomething(assertType('Bug6934\Foo', $foo));
+	assertType('Bug6934\Foo|null', $foo);
 }

tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php

@@ -3945,6 +3945,15 @@ public function testBug7369(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.0')]
+	public function testBug6934(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkNullables = true;
+		$this->checkUnionTypes = true;
+		$this->analyse([__DIR__ . '/data/bug-6934.php'], []);
+	}
+
 	public function testBug11463(): void
 	{
 		$this->checkThisOnly = false;

tests/PHPStan/Rules/Methods/data/bug-6934.php

@@ -0,0 +1,11 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug6934Rule;
+
+use DOMNode;
+
+function removeFromParent(?DOMNode $node): void {
+	$node?->parentNode?->removeChild($node);
+}