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
|
// { dg-do compile { target c++20 } }
template<class T>
struct X
{
T first{};
X& operator=(const X&) = delete;
X& operator=(const X&) requires requires (T& t) { t = t; } { return *this; }
};
// C++20 std::pair<const int, int>:
using cxx20_pair = X<const int>;
static_assert( __is_trivially_constructible(cxx20_pair, const cxx20_pair&), "" );
static_assert( !__is_assignable(cxx20_pair&, const cxx20_pair&), "" );
static_assert( __is_trivially_copyable(cxx20_pair), "" );
template<bool, typename, typename F> struct conditional { using type = F; };
template<typename T, typename F> struct conditional<true, T, F> { using type = T; };
struct base
{
base() = default;
~base() = default;
base(const base&) = default;
base& operator=(const base&) = delete;
};
struct nope;
template<class T>
struct Y : base
{
T first{};
Y& operator=(typename conditional<__is_assignable(T&, const T&), const Y&, const nope&>::type)
{ return *this; }
};
// C++17 std::pair<const int, int>:
using cxx17_pair = Y<const int>;
static_assert( __is_trivially_constructible(cxx17_pair, const cxx17_pair&), "" );
static_assert( ! __is_assignable(cxx17_pair&, const cxx17_pair&), "" );
static_assert( __is_trivially_copyable(cxx17_pair), "???" );
|
