1 // P0892R2
2 // { dg-do compile }
3 // { dg-options "-std=c++2a -fconcepts" }
4
5 #include <type_traits>
6
7 template <typename T1, typename T2>
8 struct pair {
9 template <typename U1=T1, typename U2=T2>
10 requires std::is_constructible_v<T1, U1> &&
11 std::is_constructible_v<T2, U2>
12 explicit(!std::is_convertible_v<U1, T1> ||
13 !std::is_convertible_v<U2, T2>)
pairpair14 constexpr pair(U1&&, U2&&) { }
15 };
16
17 void
foo()18 foo ()
19 {
20 pair<int, int> p{1, 2};
21 pair<int, int> p2 = {1, 2};
22 }
23