Fix GH-16190: Using reflection to call Dom\Node::__construct causes assertion failure

Closes GH-16193.

NEWS

@@ -31,6 +31,8 @@ PHP                                                                        NEWS
     DOMElement->getAttributeNames()). (nielsdos)
   . Fixed bug GH-16151 (Assertion failure in ext/dom/parentnode/tree.c).
     (nielsdos)
+  . Fixed bug GH-16190 (Using reflection to call Dom\Node::__construct
+    causes assertion failure). (nielsdos)
 
 - FPM:
   . Fixed bug GHSA-865w-9rf3-2wh5 (Logs from childrens may be altered).

ext/dom/node.c

@@ -2548,7 +2548,7 @@ PHP_METHOD(Dom_Node, compareDocumentPosition)
 
 PHP_METHOD(Dom_Node, __construct)
 {
-	ZEND_UNREACHABLE();
+	zend_throw_error(NULL, "Cannot directly construct %s, use document methods instead", ZSTR_VAL(Z_OBJCE_P(ZEND_THIS)->name));
 }
 
 PHP_METHOD(DOMNode, __sleep)

ext/dom/tests/gh16190.phpt

@@ -0,0 +1,18 @@
+--TEST--
+GH-16190 (Using reflection to call Dom\Node::__construct causes assertion failure)
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$doc = Dom\XMLDocument::createEmpty();
+$rm = new ReflectionMethod($doc, '__construct');
+try {
+    $rm->invoke($doc);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+Cannot directly construct Dom\XMLDocument, use document methods instead