Index: is-a.h
===================================================================
--- is-a.h	(revision 217985)
+++ is-a.h	(working copy)
@@ -147,10 +147,26 @@ struct is_a_helper
 {
   template <typename U>
   static inline bool test (U *p);
+  static inline bool test (T *) { return true; }
   template <typename U>
   static inline T cast (U *p);
 };

+
+template <typename T>
+struct is_a_helper<const T*>
+{
+  template <typename U>
+  static inline bool test (const U *p);
+  template <typename U>
+  static inline bool test (U *p) {return test(const_cast<const U*>(p));}
+  static inline bool test (const T *) { return true; }
+  template <typename U>
+  static inline const T *cast (const U *p);
+  template <typename U>
+  static inline const T *cast (U *p) { return cast(const_cast<const U*>(p)); }
+};
+
 /* Note that we deliberately do not define the 'test' member template.  Not
    doing so will result in a build-time error for type relationships that have
    not been defined, rather than a run-time error.  See the discussion above
@@ -169,6 +185,15 @@ is_a_helper <T>::cast (U *p)
 }


+template <typename T>
+template <typename U>
+inline const T*
+is_a_helper <const T*>::cast (const U *p)
+{
+  return reinterpret_cast <const T*> (p);
+}
+
+
 /* The public interface.  */

 /* A generic test for a type relationship.  See the discussion above for when