1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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
#include <type_traits>
#include "mongo/stdx/type_traits.h"
namespace mongo {
namespace concept {
/**
* The Constructable trait indicates whether `T` is constructible from `Constructible`.
*
* RETURNS: true if `T{ std::declval< Constructible >() }` is a valid expression and false
* otherwise.
*/
template <typename T, typename Constructible, typename = void>
struct is_constructible : std::false_type {};
template <typename T, typename Constructible>
struct is_constructible<T,
Constructible,
stdx::void_t<decltype(T{std::declval<Constructible<T>>()})>>
: std::true_type {};
/**
* The Constructable concept models a type which can be passed to a single-argument constructor of
* `T`.
* This is not possible to describe in the type `Constructible`.
*
* The expression: `T{ std::declval< Constructible< T > >() }` should be valid.
*
* This concept is more broadly applicable than `ConvertibleTo`. `ConvertibleTo` uses implicit
* conversion, whereas `Constructible` uses direct construction.
*/
template <typename T>
struct Constructible {};
} // namespace concept
} // namespace mongo
|
