Add Persistent::Upcast.

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 576 matching lines @@
     if (!that.IsEmpty()) T::Cast(*that);
 #endif
     return reinterpret_cast<Persistent<T>&>(that);
   }
 
   template <class S> V8_INLINE(Persistent<S>& As()) { // NOLINT
     return Persistent<S>::Cast(*this);
   }
 #endif
 
+  template <class S> V8_INLINE(
+      static Persistent<T>& Upcast(Persistent<S>& that)) { // NOLINT

[Sven Panne, 2013/06/05 07:08:49]

How does this relate to Persistent::Cast? It looks like it's the same, but with
an additional TYPE_CHECK. Do we really need this plethora of casting mehods
(Cast/As/Upcast)? This is currently a totally incomprehensible mess... :-/

Apart from that a tiny formatting nit: Breaking the line before V8_INLINE makes
the formatting less surprising.

+    TYPE_CHECK(T, S);
+    return reinterpret_cast<Persistent<T>&>(that);
+  }
+
   V8_DEPRECATED(static Persistent<T> New(Handle<T> that));
 
   /**
    * Creates a new persistent handle for an existing local or persistent handle.
    */
   // TODO(dcarney): remove before cutover
   V8_INLINE(static Persistent<T> New(Isolate* isolate, Handle<T> that));
 #ifndef V8_USE_UNSAFE_HANDLES
   // TODO(dcarney): remove before cutover
   V8_INLINE(static Persistent<T> New(Isolate* isolate, Persistent<T> that));
@@ skipping 5669 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_