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base/optional.h

 // Copyright 2016 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 BASE_OPTIONAL_H_
 #define BASE_OPTIONAL_H_
 
 #include "base/logging.h"
 #include "base/memory/aligned_memory.h"
 
 namespace base {
 
 // Specification:
 // http://en.cppreference.com/w/cpp/experimental/optional/in_place_t
 struct in_place_t {};
 
 // Specification:
 // http://en.cppreference.com/w/cpp/experimental/optional/nullopt_t
 struct nullopt_t {
   explicit nullopt_t(int) { }
 };
 
 // Specification:
 // http://en.cppreference.com/w/cpp/experimental/optional/in_place
 const in_place_t in_place{};
 
 // Specification:
 // http://en.cppreference.com/w/cpp/experimental/optional/nullopt
-const nullopt_t nullopt(0);
+// const nullopt_t nullopt(0);

[Yoav Weiss, 2016/03/29 22:05:45]

should be deleted?

[Marijn Kruisselbrink, 2016/04/20 01:45:03]

This was an artifact of me basing this CL on a version of the base::optional
patch that didn't actually compile. Now with base::optional landed this is
indeed no longer needed.

 
 // base::Optional is a Chromium version of the C++ library experimental optional
 // class: http://en.cppreference.com/w/cpp/experimental/optional/optional
 // The following known differences apply:
 // - 'constexpr' is not used because it is currently banned from Chromium.
 // - The constructor and emplace method using initializer_list are not
 //   implemented because 'initializer_list' is banned from Chromium.
 // - No exceptions are thrown, because they are banned from Chromium.
 // - Private member |val| (for exposition) is not implemented.
 // - The destructor doesn't use std::std::is_trivially_destructible.
@@ skipping 372 matching lines @@
 template <class T>
 void swap(Optional<T>& lhs, Optional<T>& rhs) {
   lhs.swap(rhs);
 }
 
 // TODO: implement hash function.
 
 }  // namespace base
 
 #endif // BASE_OPTIONAL_H_