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Merge pull request #13 from zeus-cpp/feat-lwg-3886
Implement LWG-3886 and add missing template 'rebind'
2 parents c2a6d6a + 9d5e45c commit 361a337

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‎README.md‎

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@@ -17,6 +17,7 @@ Implemented LWG Issues:
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- [x] [LWG-3940](https://wg21.link/lwg3940) `std::expected<void, E>::value()` also needs `E` to be copy constructible
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- [x] [LWG-4026](https://wg21.link/lwg4026) Assignment operators of `std::expected` should propagate triviality
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- [x] [LWG-3877](https://wg21.link/lwg3877) incorrect constraints on const-qualified monadic overloads for `std::expected`
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- [x] [LWG-3886](https://wg21.link/lwg3886) Monad mo' problems
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Enhancements:
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‎include/zeus/expected.hpp‎

Lines changed: 27 additions & 11 deletions
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@@ -942,7 +942,10 @@ struct copy_assign_base<T, E, true, false> : move_ctor_base<T, E>
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copy_assign_base(copy_assign_base &&rhs) = default;
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constexpr copy_assign_base &operator=(const copy_assign_base &rhs) //
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noexcept(std::is_nothrow_copy_constructible_v<T> && std::is_nothrow_copy_assignable_v<T> && std::is_nothrow_copy_constructible_v<E> && std::is_nothrow_copy_assignable_v<E>)
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noexcept(
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std::is_nothrow_copy_constructible_v<T> && std::is_nothrow_copy_assignable_v<T> && std::is_nothrow_copy_constructible_v<E> &&
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std::is_nothrow_copy_assignable_v<E>
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)
946949
{
947950
if (this->m_has_val && rhs.m_has_val)
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{
@@ -1063,7 +1066,10 @@ struct move_assign_base<T, E, true, false> : copy_assign_base<T, E>
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move_assign_base &operator=(const move_assign_base &rhs) = default;
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constexpr move_assign_base &operator=(move_assign_base &&rhs) //
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noexcept(std::is_nothrow_move_constructible_v<T> && std::is_nothrow_move_assignable_v<T> && std::is_nothrow_move_constructible_v<E> && std::is_nothrow_move_assignable_v<E>)
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noexcept(
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std::is_nothrow_move_constructible_v<T> && std::is_nothrow_move_assignable_v<T> && std::is_nothrow_move_constructible_v<E> &&
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std::is_nothrow_move_assignable_v<E>
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)
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{
10681074
if (this->m_has_val && rhs.m_has_val)
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{
@@ -1194,6 +1200,9 @@ class expected
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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template<class U>
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using rebind = expected<U, error_type>;
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// default constructors
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constexpr expected() = default;
@@ -1286,15 +1295,18 @@ class expected
12861295
// expected(U &&)
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// implicit
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template<class U = T, std::enable_if_t<std::is_convertible_v<U, T>> * = nullptr, expected_detail::enable_forward_t<T, E, U> * = nullptr>
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template<
1299+
class U = std::remove_cv_t<T>,
1300+
std::enable_if_t<std::is_convertible_v<U, T>> * = nullptr,
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expected_detail::enable_forward_t<T, E, U> * = nullptr>
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constexpr expected(U &&v) noexcept(std::is_nothrow_constructible_v<T, U>)
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: expected(std::in_place, std::forward<U>(v))
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{
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}
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// explicit
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template<
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class U = T,
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class U = std::remove_cv_t<T>,
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std::enable_if_t<!std::is_convertible_v<U, T>> * = nullptr,
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expected_detail::enable_forward_t<T, E, U> * = nullptr>
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constexpr explicit expected(U &&v) noexcept(std::is_nothrow_constructible_v<T, U>)
@@ -1418,7 +1430,7 @@ class expected
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// assignments
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14201432
template<
1421-
class U = T, //
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class U = std::remove_cv_t<T>,
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std::enable_if_t< //
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!std::is_same_v<expected, expected_detail::remove_cvref_t<U>> && //
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!expected_detail::is_specialization_v<expected_detail::remove_cvref_t<U>, unexpected> && //
@@ -1544,14 +1556,15 @@ class expected
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}
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template<class OT = T, class OE = E>
1547-
constexpr
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std::enable_if_t<
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constexpr std::enable_if_t<
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std::is_swappable_v<OT> && std::is_swappable_v<OE> && //
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std::is_move_constructible_v<OT> && std::is_move_constructible_v<OE> && //
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(std::is_nothrow_move_constructible_v<OT> || std::is_nothrow_move_constructible_v<OE>)>
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swap(expected &rhs) //
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noexcept(std::is_nothrow_move_constructible_v<T> && std::is_nothrow_swappable_v<T> && //
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std::is_nothrow_move_constructible_v<E> && std::is_nothrow_swappable_v<E>)
1564+
noexcept(
1565+
std::is_nothrow_move_constructible_v<T> && std::is_nothrow_swappable_v<T> && //
1566+
std::is_nothrow_move_constructible_v<E> && std::is_nothrow_swappable_v<E>
1567+
)
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{
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using std::swap;
15571570
if (this->m_has_val && rhs.m_has_val)
@@ -1688,7 +1701,7 @@ class expected
16881701
return std::move(err());
16891702
}
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template<class U>
1704+
template<class U = std::remove_cv_t<T>>
16921705
constexpr T value_or(U &&v) const & //
16931706
noexcept(std::is_nothrow_copy_constructible_v<T> && expected_detail::is_nothrow_convertible_v<U, T>)
16941707
{
@@ -1703,7 +1716,7 @@ class expected
17031716
return static_cast<T>(std::forward<U>(v));
17041717
}
17051718
}
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template<class U>
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template<class U = std::remove_cv_t<T>>
17071720
constexpr T value_or(U &&v) && //
17081721
noexcept(std::is_nothrow_move_constructible_v<T> && expected_detail::is_nothrow_convertible_v<U, T>)
17091722
{
@@ -2143,6 +2156,9 @@ class expected<void, E>
21432156
typedef E error_type;
21442157
typedef unexpected<E> unexpected_type;
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template<class U>
2160+
using rebind = expected<U, error_type>;
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constexpr expected() = default;
21472163
constexpr expected(const expected &rhs) = default;
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constexpr expected(expected &&rhs) = default;

‎tests/test_expected/CMakeLists.txt‎

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@@ -5,6 +5,7 @@ set(SOURCES
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monadic_tests.cpp
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noexcept_tests.cpp
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equality_tests.cpp
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lwg_3886_tests.cpp
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test_expected_main.cpp
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)
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‎tests/test_expected/lwg_3886_tests.cpp‎

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@@ -0,0 +1,72 @@
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#include <catch2/catch_all.hpp>
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#include <zeus/expected.hpp>
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5+
using namespace zeus;
6+
7+
namespace
8+
{
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10+
struct ConstructModeDistinction
11+
{
12+
enum ConstructedMode
13+
{
14+
kDefault,
15+
kCopy,
16+
kMove,
17+
kCopyAssign,
18+
kMoveAssign,
19+
};
20+
21+
constexpr ConstructModeDistinction() noexcept
22+
: mode(kDefault)
23+
{
24+
}
25+
constexpr ConstructModeDistinction(ConstructModeDistinction const&) noexcept
26+
: mode(kCopy)
27+
{
28+
}
29+
constexpr ConstructModeDistinction(ConstructModeDistinction&&) noexcept
30+
: mode(kMove)
31+
{
32+
}
33+
constexpr ConstructModeDistinction& operator=(ConstructModeDistinction&&) noexcept
34+
{
35+
mode = kMoveAssign;
36+
return *this;
37+
}
38+
constexpr ConstructModeDistinction& operator=(ConstructModeDistinction const&) noexcept
39+
{
40+
mode = kCopyAssign;
41+
return *this;
42+
}
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ConstructedMode mode;
45+
};
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} // namespace
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SCENARIO("Monad mo' problems", "[LWG-3886]")
50+
{
51+
using T = const ConstructModeDistinction;
52+
using E = int;
53+
54+
// FIXME LWG-3891
55+
//SECTION("constructor")
56+
//{
57+
// expected<T, E> const e({});
58+
// CHECK(e.value().mode == T::kMove);
59+
//}
60+
//SECTION("assignment")
61+
//{
62+
// expected<T, E> e {zeus::unexpect};
63+
// e = {};
64+
// CHECK(e.value().mode == T::kMove);
65+
//}
66+
67+
SECTION("value_or()")
68+
{
69+
expected<T, E> const e {zeus::unexpect};
70+
CHECK(e.value_or({}).mode == T::kMove);
71+
}
72+
}

‎tests/third_party/msvc/CMakeLists.txt‎

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@@ -1,3 +1,5 @@
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include_directories(SYSTEM "include")
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add_subdirectory(msvc_stl_p0323r12_test)
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if (MSVC_TOOLSET_VERSION GREATER_EQUAL 143)
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# can only built with v143 and later

‎tests/third_party/msvc/include/is_permissive.hpp‎

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@@ -0,0 +1,31 @@
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// Copyright (c) Microsoft Corporation.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#pragma once
5+
6+
#include <yvals_core.h>
7+
8+
namespace detail {
9+
constexpr bool permissive() {
10+
return false;
11+
}
12+
13+
template <class>
14+
struct PermissiveTestBase {
15+
static constexpr bool permissive() {
16+
return true;
17+
}
18+
};
19+
20+
template <class T>
21+
struct PermissiveTest : PermissiveTestBase<T> {
22+
static constexpr bool test() {
23+
return permissive();
24+
}
25+
};
26+
} // namespace detail
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template <class T>
29+
constexpr bool is_permissive_v = detail::PermissiveTest<T>::test();
30+
31+
_INLINE_VAR constexpr bool is_permissive = is_permissive_v<int>;

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