Add test

Author: Girgias

tests/PHPStan/Rules/Properties/AccessPropertiesRuleTest.php

@@ -959,4 +959,12 @@ public function testTraitMixin(): void
 		$this->analyse([__DIR__ . '/data/trait-mixin.php'], []);
 	}
 
+	public function testDomExtensionLegacyTemplateNodes(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkUnionTypes = true;
+		$this->checkDynamicProperties = true;
+		$this->analyse([__DIR__ . '/data/dom-legacy-ext-template-nodes.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/dom-legacy-ext-template-nodes.php

@@ -0,0 +1,18 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+
+function (\DOMNode $node): void {
+	assertType(DOMNamedNodeMap::class . '<' . DOMAttr::class . '>', $node->attributes);
+};
+
+function parse(\DOMElement $node): void
+{
+	assertType(DOMNamedNodeMap::class . '<' . DOMAttr::class . '>', $node->attributes);
+	$attribute = $node->attributes->getNamedItem('class');
+	if ($attribute === null) {
+		return;
+	}
+	assertType(DOMAttr::class, $attribute);
+	assertType('string', $attribute->value);
+}