Mojo C++ bindings: support enum validation.

mojo/public/cpp/bindings/lib/bindings_internal.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_BINDINGS_INTERNAL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_BINDINGS_INTERNAL_H_
 
 #include <stdint.h>
 
 #include "mojo/public/cpp/bindings/lib/interface_id.h"
@@ skipping 76 matching lines @@
   return temp;
 }
 
 template <typename H>
 struct IsHandle {
   enum { value = IsBaseOf<Handle, H>::value };
 };
 
 template <typename T>
 struct IsUnionDataType {
+  typedef char (*EnsureTypeIsComplete)[sizeof(T)];

[Ken Rockot(use gerrit already), 2016/01/26 15:39:20]

nit: any reason not to use a c++11 alias here and below? just convention?

[yzshen1, 2016/01/26 18:16:04]

Done. I also refactored a little bit. Thanks!

+
   template <typename U>
   static YesType Test(const typename U::MojomUnionDataType*);
 
   template <typename U>
   static NoType Test(...);
 
   static const bool value =
       sizeof(Test<T>(0)) == sizeof(YesType) && !IsConst<T>::value;
 };
 
+template <typename T>
+struct IsEnumDataType {
+  typedef char (*EnsureTypeIsComplete)[sizeof(T)];
+
+  template <typename U>
+  static YesType Test(const typename U::MojomEnumDataType*);
+
+  template <typename U>
+  static NoType Test(...);
+
+  static const bool value =
+      sizeof(Test<T>(0)) == sizeof(YesType) && !IsConst<T>::value;
+};
+
 template <typename T, bool move_only = IsMoveOnlyType<T>::value>
 struct WrapperTraits;
 
 template <typename T>
 struct WrapperTraits<T, false> {
   typedef T DataType;
 };
 template <typename H>
 struct WrapperTraits<ScopedHandleBase<H>, true> {
   typedef H DataType;
 };
 template <typename S>
 struct WrapperTraits<StructPtr<S>, true> {
   typedef typename S::Data_* DataType;
 };
 template <typename S>
 struct WrapperTraits<InlinedStructPtr<S>, true> {
   typedef typename S::Data_* DataType;
 };
 template <typename S>
 struct WrapperTraits<S, true> {
   typedef typename S::Data_* DataType;
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_BINDINGS_INTERNAL_H_