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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// REQUIRES: std-at-least-c++17
// <utility>
// template<class T1, class T2>
// pair(T1, T2) -> pair<T1, T2>;
// Test that the explicit deduction guide for std::pair correctly decays function lvalues and
// behaves different from std::make_pair.
#include <cassert>
#include <functional>
#include <type_traits>
#include <utility>
#include "test_macros.h"
void dummy() {}
constexpr void test_decay() {
char arr[1]{};
std::pair pr(arr, dummy);
ASSERT_SAME_TYPE(decltype(pr), std::pair<char*, void (*)()>);
assert(pr == std::make_pair(arr, dummy));
}
TEST_CONSTEXPR_CXX20 void test_unwrap() {
int n = 0;
std::pair pr(std::ref(n), dummy);
ASSERT_SAME_TYPE(decltype(pr), std::pair<std::reference_wrapper<int>, void (*)()>);
static_assert(!std::is_same_v<decltype(pr), decltype(std::make_pair(std::ref(n), dummy))>);
assert(&(pr.first.get()) == &n);
assert(pr.second == dummy);
}
constexpr bool test() {
test_decay();
if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED)
test_unwrap();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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