1 /* Copyright (C) 2017-2024 Free Software Foundation, Inc.
3 This file is part of GDB.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 #ifndef COMMON_TRAITS_H
19 #define COMMON_TRAITS_H
21 #include <type_traits>
25 /* Implementation of the detection idiom:
27 - http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf
28 - http://en.cppreference.com/w/cpp/experimental/is_detected
35 ~nonesuch () = delete;
36 nonesuch (const nonesuch
&) = delete;
37 void operator= (const nonesuch
&) = delete;
40 namespace detection_detail
{
41 /* Implementation of the detection idiom (negative case). */
42 template<typename Default
, typename AlwaysVoid
,
43 template<typename
...> class Op
, typename
... Args
>
46 using value_t
= std::false_type
;
50 /* Implementation of the detection idiom (positive case). */
51 template<typename Default
, template<typename
...> class Op
, typename
... Args
>
52 struct detector
<Default
, std::void_t
<Op
<Args
...>>, Op
, Args
...>
54 using value_t
= std::true_type
;
55 using type
= Op
<Args
...>;
58 /* Detect whether Op<Args...> is a valid type, use Default if not. */
59 template<typename Default
, template<typename
...> class Op
,
61 using detected_or
= detector
<Default
, void, Op
, Args
...>;
63 /* Op<Args...> if that is a valid type, otherwise Default. */
64 template<typename Default
, template<typename
...> class Op
,
67 = typename detected_or
<Default
, Op
, Args
...>::type
;
69 } /* detection_detail */
71 template<template<typename
...> class Op
, typename
... Args
>
73 = typename
detection_detail::detector
<nonesuch
, void, Op
, Args
...>::value_t
;
75 template<template<typename
...> class Op
, typename
... Args
>
77 = typename
detection_detail::detector
<nonesuch
, void, Op
, Args
...>::type
;
79 template<typename Default
, template<typename
...> class Op
, typename
... Args
>
80 using detected_or
= detection_detail::detected_or
<Default
, Op
, Args
...>;
82 template<typename Default
, template<typename
...> class Op
, typename
... Args
>
83 using detected_or_t
= typename detected_or
<Default
, Op
, Args
...>::type
;
85 template<typename Expected
, template<typename
...> class Op
, typename
... Args
>
86 using is_detected_exact
= std::is_same
<Expected
, detected_t
<Op
, Args
...>>;
88 template<typename To
, template<typename
...> class Op
, typename
... Args
>
89 using is_detected_convertible
90 = std::is_convertible
<detected_t
<Op
, Args
...>, To
>;
92 /* A few trait helpers, mainly stolen from libstdc++. Uppercase
93 because "and/or", etc. are reserved keywords. */
95 template<typename Predicate
>
96 struct Not
: public std::integral_constant
<bool, !Predicate::value
>
103 struct Or
<> : public std::false_type
106 template<typename B1
>
107 struct Or
<B1
> : public B1
110 template<typename B1
, typename B2
>
112 : public std::conditional
<B1::value
, B1
, B2
>::type
115 template<typename B1
,typename B2
,typename B3
, typename
... Bn
>
116 struct Or
<B1
, B2
, B3
, Bn
...>
117 : public std::conditional
<B1::value
, B1
, Or
<B2
, B3
, Bn
...>>::type
120 template<typename
...>
124 struct And
<> : public std::true_type
127 template<typename B1
>
128 struct And
<B1
> : public B1
131 template<typename B1
, typename B2
>
133 : public std::conditional
<B1::value
, B2
, B1
>::type
136 template<typename B1
, typename B2
, typename B3
, typename
... Bn
>
137 struct And
<B1
, B2
, B3
, Bn
...>
138 : public std::conditional
<B1::value
, And
<B2
, B3
, Bn
...>, B1
>::type
141 /* Concepts-light-like helper to make SFINAE logic easier to read. */
142 template<typename Condition
>
143 using Requires
= typename
std::enable_if
<Condition::value
, void>::type
;
146 #endif /* COMMON_TRAITS_H */