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[libc++] Fix LWG3589 "The const lvalue reference overload of get for subrange..." 

https://cplusplus.github.io/LWG/issue3589

Differential Revision: https://reviews.llvm.org/D117961
This commit is contained in:
Arthur O'Dwyer 2022-01-22 14:33:12 -05:00
parent aefb2e134d
commit 6a56d5cc25
3 changed files with 64 additions and 15 deletions
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2
libcxx/docs/Status/Cxx2bIssues.csv
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@ -130,7 +130,7 @@
`3580 <https://wg21.link/LWG3580>`__,"``iota_view``'s ``iterator``'s binary ``operator+`` should be improved","October 2021","|Complete|","14.0","|ranges|"
`3581 <https://wg21.link/LWG3581>`__,"The range constructor makes ``basic_string_view`` not trivially move constructible","October 2021","|Complete|","14.0","|ranges|"
`3585 <https://wg21.link/LWG3585>`__,"``variant`` converting assignment with immovable alternative","October 2021","",""
`3589 <https://wg21.link/LWG3589>`__,"The ``const`` lvalue reference overload of ``get`` for ``subrange`` does not constrain ``I`` to be ``copyable`` when ``N == 0``","October 2021","","","|ranges|"
`3589 <https://wg21.link/LWG3589>`__,"The ``const`` lvalue reference overload of ``get`` for ``subrange`` does not constrain ``I`` to be ``copyable`` when ``N == 0``","October 2021","|Complete|","14.0","|ranges|"
`3590 <https://wg21.link/LWG3590>`__,"``split_view::base() const &`` is overconstrained","October 2021","","","|ranges|"
`3591 <https://wg21.link/LWG3591>`__,"``lazy_split_view<input_view>::inner-iterator::base() &&`` invalidates outer iterators","October 2021","","","|ranges|"
`3592 <https://wg21.link/LWG3592>`__,"``lazy_split_view`` needs to check the simpleness of Pattern","October 2021","","","|ranges|"

Can't render this file because it has a wrong number of fields in line 2.

2
libcxx/include/__ranges/subrange.h
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@ -227,7 +227,7 @@ namespace ranges {
-> subrange<iterator_t<_Range>, sentinel_t<_Range>, subrange_kind::sized>;
template<size_t _Index, class _Iter, class _Sent, subrange_kind _Kind>
requires (_Index < 2)
requires ((_Index == 0 && copyable<_Iter>) || _Index == 1)
_LIBCPP_HIDE_FROM_ABI
constexpr auto get(const subrange<_Iter, _Sent, _Kind>& __subrange) {
if constexpr (_Index == 0)

75
libcxx/test/std/ranges/range.utility/range.subrange/get.pass.cpp
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@ -17,26 +17,75 @@
#include <cassert>
#include "test_macros.h"
#include "test_iterators.h"
#include "types.h"
template<size_t I, class S>
concept GetInvocable = requires {
concept HasGet = requires {
std::get<I>(std::declval<S>());
};
static_assert( GetInvocable<0, std::ranges::subrange<int*>>);
static_assert( GetInvocable<1, std::ranges::subrange<int*>>);
static_assert(!GetInvocable<2, std::ranges::subrange<int*>>);
static_assert(!GetInvocable<3, std::ranges::subrange<int*>>);
static_assert( HasGet<0, std::ranges::subrange<int*>>);
static_assert( HasGet<1, std::ranges::subrange<int*>>);
static_assert(!HasGet<2, std::ranges::subrange<int*>>);
static_assert(!HasGet<3, std::ranges::subrange<int*>>);
constexpr bool test() {
std::ranges::subrange<int*> a(globalBuff, globalBuff + 8, 8);
assert(std::get<0>(a) == a.begin());
assert(std::get<1>(a) == a.end());
assert(a.begin() == std::get<0>(std::move(a)));
std::ranges::subrange<int*> b(globalBuff, globalBuff + 8, 8);
assert(b.end() == std::get<1>(std::move(b)));
{
using It = int*;
using Sent = sentinel_wrapper<int*>;
int a[] = {1, 2, 3};
using R = std::ranges::subrange<It, Sent, std::ranges::subrange_kind::unsized>;
R r = R(It(a), Sent(It(a + 3)));
ASSERT_SAME_TYPE(decltype(std::get<0>(r)), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(r)), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<R&&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<R&&>(r))), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<const R&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&>(r))), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<const R&&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&&>(r))), Sent);
assert(base(std::get<0>(r)) == a); // copy from It
assert(base(base(std::get<1>(r))) == a + 3); // copy from Sent
assert(base(std::get<0>(std::move(r))) == a); // copy from It
assert(base(base(std::get<1>(std::move(r)))) == a + 3); // copy from Sent
}
{
using It = int*;
using Sent = sentinel_wrapper<int*>;
int a[] = {1, 2, 3};
using R = std::ranges::subrange<It, Sent, std::ranges::subrange_kind::sized>;
R r = R(It(a), Sent(It(a + 3)), 3);
ASSERT_SAME_TYPE(decltype(std::get<0>(r)), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(r)), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<R&&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<R&&>(r))), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<const R&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&>(r))), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<const R&&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&&>(r))), Sent);
assert(base(std::get<0>(r)) == a); // copy from It
assert(base(base(std::get<1>(r))) == a + 3); // copy from Sent
assert(base(std::get<0>(std::move(r))) == a); // copy from It
assert(base(base(std::get<1>(std::move(r)))) == a + 3); // copy from Sent
}
{
// Test the fix for LWG 3589.
using It = cpp20_input_iterator<int*>;
using Sent = sentinel_wrapper<It>;
int a[] = {1, 2, 3};
using R = std::ranges::subrange<It, Sent>;
R r = R(It(a), Sent(It(a + 3)));
static_assert(!HasGet<0, R&>);
ASSERT_SAME_TYPE(decltype(std::get<1>(r)), Sent);
ASSERT_SAME_TYPE(decltype(std::get<0>(static_cast<R&&>(r))), It);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<R&&>(r))), Sent);
static_assert(!HasGet<0, const R&>);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&>(r))), Sent);
static_assert(!HasGet<0, const R&&>);
ASSERT_SAME_TYPE(decltype(std::get<1>(static_cast<const R&&>(r))), Sent);
assert(base(base(std::get<1>(r))) == a + 3); // copy from Sent
assert(base(std::get<0>(std::move(r))) == a); // move from It
assert(base(base(std::get<1>(std::move(r)))) == a + 3); // copy from Sent
}
return true;
}