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Allow reflection of aggregates with non movable fields if guaranteed copy elision is on

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This commit is contained in:
Antony Polukhin
2021-03-24 09:58:20 +03:00
parent 36c020b032
commit 638fefedd0
2 changed files with 49 additions and 2 deletions
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6
include/boost/pfr/detail/fields_count.hpp
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@@ -41,8 +41,8 @@ struct ubiq_lref_constructor {
///////////////////// Structure that can be converted to rvalue reference to anything
struct ubiq_rref_constructor {
std::size_t ignore;
template <class Type> /*constexpr*/ operator Type&&() const && noexcept { // Allows initialization of rvalue reference fields and move-only types
return detail::unsafe_declval<Type&&>();
template <class Type> /*constexpr*/ operator Type() const && noexcept { // Allows initialization of rvalue reference fields and move-only types
return detail::unsafe_declval<Type>();
};
};
@@ -210,6 +210,7 @@ constexpr std::size_t fields_count() noexcept {
"====================> Boost.PFR: Attempt to get fields count on a reference. This is not allowed because that could hide an issue and different library users expect different behavior in that case."
);
#ifndef __cpp_guaranteed_copy_elision
static_assert(
std::is_copy_constructible<std::remove_all_extents_t<type>>::value || (
std::is_move_constructible<std::remove_all_extents_t<type>>::value
@@ -217,6 +218,7 @@ constexpr std::size_t fields_count() noexcept {
),
"====================> Boost.PFR: Type and each field in the type must be copy constructible (or move constructible and move assignable)."
);
#endif // #ifndef __cpp_guaranteed_copy_elision
static_assert(
!std::is_polymorphic<type>::value,

45
test/run/non_movable.cpp Normal file
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@@ -0,0 +1,45 @@
// Copyright (c) 2018-2021 Antony Polukhin
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/pfr/tuple_size.hpp>
#include <boost/core/lightweight_test.hpp>
struct X {
X() = default;
X(X&&) = delete;
X(const X&) = delete;
X& operator=(X&&) = delete;
X& operator=(const X&) = delete;
};
struct S { X x0; X x1; int x2; X x3; };
int main() {
#ifdef __cpp_guaranteed_copy_elision
static_assert(boost::pfr::tuple_size_v<S> == 4, "");
struct S5_0 { int x0; int x1; int x2; int x3; X x4; };
static_assert(boost::pfr::tuple_size_v<S5_0> == 5, "");
struct S5_1 { X x0; int x1; int x2; int x3; int x4; };
static_assert(boost::pfr::tuple_size_v<S5_1> == 5, "");
struct S5_2 { int x0; int x1; X x2; int x3; int x4; };
static_assert(boost::pfr::tuple_size_v<S5_2> == 5, "");
struct S5_3 { int x0; int x1; X x2; int x3; X x4; };
static_assert(boost::pfr::tuple_size_v<S5_3> == 5, "");
struct S5_4 { X x0; X x1; X x2; X x3; X x4; };
static_assert(boost::pfr::tuple_size_v<S5_4> == 5, "");
struct S6 { X x0; X x1; X x2; X x3; X x4; X x5;};
static_assert(boost::pfr::tuple_size_v<S6> == 6, "");
#endif // #ifdef __cpp_guaranteed_copy_elision
return boost::report_errors();
}