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LWG-3872: basic_const_iterator should have custom iter_move #3470

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Merged
StephanTLavavej merged 1 commit into from
Feb 23, 2023
+23 −2
Merged

LWG-3872: basic_const_iterator should have custom iter_move #3470

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11 changes: 10 additions & 1 deletion stl/inc/xutility
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Original file line number Diff line number Diff line change
Expand Up @@ -1758,6 +1758,9 @@ _NODISCARD constexpr const _Elem* data(initializer_list<_Elem> _Ilist) noexcept
_EXPORT_STD template <indirectly_readable _Ty>
using iter_const_reference_t = common_reference_t<const iter_value_t<_Ty>&&, iter_reference_t<_Ty>>;

template <indirectly_readable _Iter>
using _Iter_const_rvalue_reference_t = common_reference_t<const iter_value_t<_Iter>&&, iter_rvalue_reference_t<_Iter>>;

template <class _Ty>
concept _Constant_iterator = input_iterator<_Ty> && same_as<iter_const_reference_t<_Ty>, iter_reference_t<_Ty>>;

Expand Down Expand Up @@ -1810,7 +1813,8 @@ class basic_const_iterator : public _Basic_const_iterator_category<_Iter> {
private:
/* [[no_unique_address]] */ _Iter _Current{};

using _Reference = iter_const_reference_t<_Iter>;
using _Reference = iter_const_reference_t<_Iter>;
using _Rvalue_reference = _Iter_const_rvalue_reference_t<_Iter>;

_NODISCARD static _CONSTEVAL auto _Get_iter_concept() noexcept {
if constexpr (contiguous_iterator<_Iter>) {
Expand Down Expand Up @@ -2063,6 +2067,11 @@ public:
noexcept(_Se - _It._Current)) /* strengthened */ { // per LWG-3769
return _Se - _It._Current;
}

_NODISCARD_FRIEND constexpr _Rvalue_reference iter_move(const basic_const_iterator& _It) noexcept(
noexcept(static_cast<_Rvalue_reference>(_RANGES iter_move(_It._Current)))) {
return static_cast<_Rvalue_reference>(_RANGES iter_move(_It._Current));
}
};

template <class _Ty1, common_with<_Ty1> _Ty2>
Expand Down
2 changes: 1 addition & 1 deletion tests/std/tests/P2278R4_basic_const_iterator/env.lst
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@@ -1,4 +1,4 @@
# Copyright (c) Microsoft Corporation.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

RUNALL_INCLUDE ..\concepts_latest_matrix.lst
RUNALL_INCLUDE ..\strict_concepts_latest_matrix.lst
12 changes: 12 additions & 0 deletions tests/std/tests/P2278R4_basic_const_iterator/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include <cassert>
#include <iterator>
#include <memory>
#include <ranges>
#include <type_traits>
#include <utility>

Expand Down Expand Up @@ -239,6 +240,13 @@ constexpr void test_one(It iter) {
static_assert(noexcept(citer == sent) == noexcept(iter == sent)); // strengthened
}

{ // Validate basic_const_iterator::iter_move()
using Expected = common_reference_t<const iter_value_t<It>&&, iter_rvalue_reference_t<It>>;
[[maybe_unused]] same_as<Expected> decltype(auto) val = ranges::iter_move(citer);
static_assert(
noexcept(ranges::iter_move(citer)) == noexcept(static_cast<Expected>(ranges::iter_move(citer.base()))));
}

{ // Validate basic_const_iterator::base() const&
[[maybe_unused]] same_as<const It&> decltype(auto) base = citer.base();
static_assert(noexcept(citer.base()));
Expand All @@ -252,6 +260,10 @@ constexpr void test_one(It iter) {

static constexpr int some_ints[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

// Check LWG-3872
using Zipped = decltype(views::zip(some_ints) | views::as_const | views::as_rvalue);
static_assert(same_as<ranges::range_reference_t<Zipped>, tuple<const int&&>>);

struct instantiator {
template <input_iterator It>
static constexpr void call() {
Expand Down