sumty  0.1.0
Better sum types for C++
traits.hpp
1 /* Copyright 2023 Jack A Bernard Jr.
2  *
3  * Licensed under the Apache License, Version 2.0 (the License);
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an AS IS BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  * See the License for the specific language governing permissions and
13  * limitations under the License.
14  */
15 
16 #ifndef SUMTY_DETAIL_TRAITS_HPP
17 #define SUMTY_DETAIL_TRAITS_HPP
18 
19 #include <type_traits>
20 
21 #include "sumty/utils.hpp"
22 
23 namespace sumty::detail {
24 
25 template <typename T>
26 struct traits {
27  using value_type = std::remove_const_t<T>;
28  using reference = T&;
29  using const_reference = std::add_const_t<T>&;
30  using rvalue_reference = T&&;
31  using const_rvalue_reference = const T&&;
32  using pointer = T*;
33  using const_pointer = std::add_const_t<T>*;
34 
35  static inline constexpr bool is_default_constructible =
36  std::is_default_constructible_v<value_type>;
37  static inline constexpr bool is_nothrow_default_constructible =
38  std::is_nothrow_default_constructible_v<value_type>;
39  static inline constexpr bool is_copy_constructible =
40  std::is_copy_constructible_v<value_type>;
41  static inline constexpr bool is_nothrow_copy_constructible =
42  std::is_nothrow_copy_constructible_v<value_type>;
43  static inline constexpr bool is_move_constructible =
44  std::is_move_constructible_v<value_type>;
45  static inline constexpr bool is_nothrow_move_constructible =
46  std::is_nothrow_move_constructible_v<value_type>;
47  static inline constexpr bool is_destructible = std::is_destructible_v<value_type>;
48  static inline constexpr bool is_nothrow_destructible =
49  std::is_nothrow_destructible_v<value_type>;
50  static inline constexpr bool is_copy_assignable = std::is_copy_assignable_v<T>;
51  static inline constexpr bool is_nothrow_copy_assignable =
52  std::is_nothrow_copy_assignable_v<T>;
53  static inline constexpr bool is_move_assignable = std::is_move_assignable_v<T>;
54  static inline constexpr bool is_nothrow_move_assignable =
55  std::is_nothrow_move_assignable_v<T>;
56  static inline constexpr bool is_swappable = std::is_swappable_v<T>;
57  static inline constexpr bool is_nothrow_swappable = std::is_nothrow_swappable_v<T>;
58 
59  template <typename U>
60  static inline constexpr bool is_convertible_from = std::is_convertible_v<U, value_type>;
61 
62  template <typename... U>
63  static inline constexpr bool is_constructible =
64  std::is_constructible_v<value_type, U...> &&
65  (std::is_same_v<value_type, void_t> ||
66  ((sizeof...(U) != 1) || ... || !std::is_same_v<std::remove_cvref_t<U>, void_t>));
67 
68  template <typename U>
69  static inline constexpr bool is_assignable = std::is_assignable_v<reference, U>;
70 
71  template <typename... U>
72  static inline constexpr bool is_nothrow_constructible =
73  std::is_nothrow_constructible_v<value_type, U...> &&
74  (std::is_same_v<value_type, void_t> ||
75  ((sizeof...(U) != 1) || ... || !std::is_same_v<std::remove_cvref_t<U>, void_t>));
76 
77  template <typename U>
78  static inline constexpr bool is_nothrow_assignable =
79  std::is_nothrow_assignable_v<reference, U>;
80 };
81 
82 template <typename T>
83 struct traits<T&&> : traits<T> {};
84 
85 template <typename T>
86 struct traits<T&> {
87  using value_type = T&;
88  using reference = T&;
89  using const_reference = T&;
90  using rvalue_reference = T&;
91  using const_rvalue_reference = T&;
92  using pointer = T*;
93  using const_pointer = T*;
94 
95  static inline constexpr bool is_default_constructible = false;
96  static inline constexpr bool is_nothrow_default_constructible = false;
97  static inline constexpr bool is_copy_constructible = true;
98  static inline constexpr bool is_nothrow_copy_constructible = true;
99  static inline constexpr bool is_move_constructible = true;
100  static inline constexpr bool is_nothrow_move_constructible = true;
101  static inline constexpr bool is_destructible = true;
102  static inline constexpr bool is_nothrow_destructible = true;
103  static inline constexpr bool is_copy_assignable = true;
104  static inline constexpr bool is_nothrow_copy_assignable = true;
105  static inline constexpr bool is_move_assignable = true;
106  static inline constexpr bool is_nothrow_move_assignable = true;
107  static inline constexpr bool is_swappable = true;
108  static inline constexpr bool is_nothrow_swappable = true;
109 
110  template <typename U>
111  static inline constexpr bool is_convertible_from =
112  std::is_lvalue_reference_v<U> &&
113  std::is_convertible_v<typename traits<U>::pointer, pointer>;
114 
115  template <typename... U>
116  struct is_constructible_t : std::false_type {};
117 
118  template <typename U>
119  struct is_constructible_t<U>
120  : std::integral_constant<bool, std::is_convertible_v<U, pointer>> {};
121 
122  template <typename... U>
123  static inline constexpr bool is_constructible = is_constructible_t<U...>::value;
124 
125  template <typename U>
126  static inline constexpr bool is_assignable =
127  std::is_lvalue_reference_v<U> &&
128  std::is_convertible_v<typename traits<U>::pointer, pointer>;
129 
130  template <typename... U>
131  static inline constexpr bool is_nothrow_constructible = is_constructible_t<U...>::value;
132 
133  template <typename U>
134  static inline constexpr bool is_nothrow_assignable = is_assignable<U>;
135 };
136 
137 template <>
138 struct traits<void> {
139  using value_type = void;
140  using reference = void;
141  using const_reference = void;
142  using rvalue_reference = void;
143  using const_rvalue_reference = void;
144  using pointer = void;
145  using const_pointer = void;
146 
147  static inline constexpr bool is_default_constructible = true;
148  static inline constexpr bool is_nothrow_default_constructible = true;
149  static inline constexpr bool is_copy_constructible = true;
150  static inline constexpr bool is_nothrow_copy_constructible = true;
151  static inline constexpr bool is_move_constructible = true;
152  static inline constexpr bool is_nothrow_move_constructible = true;
153  static inline constexpr bool is_destructible = true;
154  static inline constexpr bool is_nothrow_destructible = true;
155  static inline constexpr bool is_copy_assignable = true;
156  static inline constexpr bool is_nothrow_copy_assignable = true;
157  static inline constexpr bool is_move_assignable = true;
158  static inline constexpr bool is_nothrow_move_assignable = true;
159  static inline constexpr bool is_swappable = true;
160  static inline constexpr bool is_nothrow_swappable = true;
161 
162  template <typename U>
163  static inline constexpr bool is_convertible_from =
164  traits<void_t>::is_convertible_from<U> || std::is_void_v<U>;
165 
166  template <typename... U>
167  static inline constexpr bool is_constructible =
168  traits<void_t>::is_constructible<U...> ||
169  ((sizeof...(U) == 1) && ... && std::is_void_v<U>);
170 
171  template <typename U>
172  static inline constexpr bool is_assignable =
173  traits<void_t>::is_assignable<U> || std::is_void_v<U>;
174 
175  template <typename... U>
176  static inline constexpr bool is_nothrow_constructible =
177  traits<void_t>::is_nothrow_constructible<U...> ||
178  ((sizeof...(U) == 1) && ... && std::is_void_v<U>);
179 
180  template <typename U>
181  static inline constexpr bool is_nothrow_assignable =
182  traits<void_t>::is_nothrow_assignable<U> || std::is_void_v<U>;
183 };
184 
185 } // namespace sumty::detail
186 
187 #endif