2 * Copyright 2015 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
20 template <class T> struct Lift : public std::false_type {
26 struct Unit::Lift<void> : public std::true_type {
31 struct is_void_or_unit : public std::conditional<
32 std::is_void<T>::value || std::is_same<Unit, T>::value,
34 std::false_type>::type