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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: c++17
// <optional>
// constexpr optional(const optional<T>&& rhs);
// C++17 said:
// If is_trivially_move_constructible_v<T> is true,
// this constructor shall be a constexpr constructor.
//
// P0602 changed this to:
// If is_trivially_move_constructible_v<T> is true, this constructor is trivial.
//
// which means that it can't be constexpr if T is not trivially move-constructible,
// because you have to do a placement new to get the value into place.
// Except in the case where it is moving from an empty optional - that could be
// made to be constexpr (and libstdc++ does so).
#include <optional>
#include <type_traits>
#include <cassert>
#include "test_macros.h"
struct S {
constexpr S() : v_(0) {}
S(int v) : v_(v) {}
constexpr S(const S &rhs) : v_(rhs.v_) {} // not trivially moveable
constexpr S( S &&rhs) : v_(rhs.v_) {} // not trivially moveable
int v_;
};
constexpr bool test() // expected-error {{constexpr function never produces a constant expression}}
{
std::optional<S> o1{3};
std::optional<S> o2 = std::move(o1);
return o2.has_value(); // return -something-
}
int main(int, char**)
{
static_assert (!std::is_trivially_move_constructible_v<S>, "" );
static_assert (test(), ""); // expected-error {{static_assert expression is not an integral constant expression}}
return 0;
}
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