SERVER-35818 Add stdx::variant

1 files changed, 90 insertions, 0 deletions

diff --git a/src/mongo/stdx/variant.h b/src/mongo/stdx/variant.h
new file mode 100644
index 00000000000..92bf6167555
--- /dev/null
+++ b/src/mongo/stdx/variant.h
@@ -0,0 +1,90 @@
+/**
+ *    Copyright (C) 2018 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#ifndef __cpp_lib_variant
+#include "third_party/variant-1.3.0/include/mpark/variant.hpp"
+#else
+#include <variant>
+#endif
+
+namespace mongo {
+namespace stdx {
+#if __cplusplus < 201703L || !defined(__cpp_lib_variant)
+using ::mpark::variant;
+using ::mpark::visit;
+using ::mpark::holds_alternative;
+using ::mpark::get;
+using ::mpark::get_if;
+
+using ::mpark::variant_size;
+using ::mpark::variant_size_v;
+using ::mpark::variant_alternative;
+using ::mpark::variant_alternative_t;
+
+constexpr auto variant_npos = ::mpark::variant_npos;
+
+using ::mpark::operator==;
+using ::mpark::operator!=;
+using ::mpark::operator<;
+using ::mpark::operator>;
+using ::mpark::operator<=;
+using ::mpark::operator>=;
+
+using ::mpark::monostate;
+using ::mpark::bad_variant_access;
+
+#else
+using ::std::variant;
+using ::std::visit;
+using ::std::holds_alternative;
+using ::std::get;
+using ::std::get_if;
+
+using ::std::variant_size;
+using ::std::variant_size_v;
+using ::std::variant_alternative;
+using ::std::variant_alternative_t;
+
+constexpr auto variant_npos = ::std::variant_npos;
+
+using ::std::operator==;
+using ::std::operator!=;
+using ::std::operator<;
+using ::std::operator>;
+using ::std::operator<=;
+using ::std::operator>=;
+
+using ::std::monostate;
+using ::std::bad_variant_access;
+
+#endif
+
+}  // namespace stdx
+}  // namespace mongo