Merge pull request #4727 from criemen/remove-abstract-classes

C++/C#/JS/Python/Java XML.qll: Remove abstract from class hierarchy.

java/ql/src/semmle/code/xml/XML.qll

@@ -4,8 +4,11 @@
 
 import semmle.files.FileSystem
 
+private class TXMLLocatable =
+  @xmldtd or @xmlelement or @xmlattribute or @xmlnamespace or @xmlcomment or @xmlcharacters;
+
 /** An XML element that has a location. */
-abstract class XMLLocatable extends @xmllocatable {
+class XMLLocatable extends @xmllocatable, TXMLLocatable {
   /** Gets the source location for this element. */
   Location getLocation() { xmllocations(this, result) }
 
@@ -33,7 +36,7 @@ abstract class XMLLocatable extends @xmllocatable {
   }
 
   /** Gets a textual representation of this element. */
-  abstract string toString();
+  string toString() { none() } // overridden in subclasses
 }
 
 /**
@@ -51,7 +54,7 @@ class XMLParent extends @xmlparent {
    * Gets a printable representation of this XML parent.
    * (Intended to be overridden in subclasses.)
    */
-  abstract string getName();
+  string getName() { none() } // overridden in subclasses
 
   /** Gets the file to which this XML parent belongs. */
   XMLFile getFile() { result = this or xmlElements(this, _, _, _, result) }