Merge pull request #2520 from max-schaefer/js/fix-2517

Approved by esbena

javascript/ql/src/semmle/javascript/XML.qll

@@ -34,6 +34,12 @@ abstract class XMLLocatable extends @xmllocatable {
  * both of which can contain other elements.
  */
 class XMLParent extends @xmlparent {
+  XMLParent() {
+    // explicitly restrict `this` to be either an `XMLElement` or an `XMLFile`;
+    // the type `@xmlparent` currently also includes non-XML files
+    this instanceof @xmlelement or xmlEncoding(this, _)
+  }
+
   /**
    * Gets a printable representation of this XML parent.
    * (Intended to be overridden in subclasses.)