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libstdc++: Implement LWG 3798 for range adaptors [PR106676]

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LWG 3798 modified the iterator_category of the iterator types for
transform_view, join_with_view, zip_transform_view and
adjacent_transform_view, to allow the iterator's reference type to be an
rvalue reference.

libstdc++-v3/ChangeLog:

	PR libstdc++/106676
	* include/bits/iterator_concepts.h (__cpp17_fwd_iterator): Use
	is_reference instead of is_value_reference.
	rvalue references.
	* include/std/ranges (transform_view:__iter_cat::_S_iter_cat):
	Likewise.
	(zip_transform_view::__iter_cat::_S_iter_cat): Likewise.
	(adjacent_transform_view::__iter_cat::_S_iter_cat): Likewise.
	(join_with_view::__iter_cat::_S_iter_cat): Likewise.
	* testsuite/std/ranges/adaptors/transform.cc: Check
	iterator_category when the transformation function returns an
	rvalue reference type.

Reviewed-by: Patrick Palka <ppalka@redhat.com>
This commit is contained in:
Jonathan Wakely 2024-10-13 22:28:16 +01:00 committed by Jonathan Wakely
parent 7d15248d41
commit 7f65f94917
No known key found for this signature in database
3 changed files with 32 additions and 6 deletions
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4
libstdc++-v3/include/bits/iterator_concepts.h
View File

@ -333,10 +333,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typename incrementable_traits<_Iter>::difference_type>;
};
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3798. Rvalue reference and iterator_category
template<typename _Iter>
concept __cpp17_fwd_iterator = __cpp17_input_iterator<_Iter>
&& constructible_from<_Iter>
&& is_lvalue_reference_v<iter_reference_t<_Iter>>
&& is_reference_v<iter_reference_t<_Iter>>
&& same_as<remove_cvref_t<iter_reference_t<_Iter>>,
typename indirectly_readable_traits<_Iter>::value_type>
&& requires(_Iter __it)

18
libstdc++-v3/include/std/ranges
View File

@ -1892,7 +1892,9 @@ namespace views::__adaptor
using _Base = transform_view::_Base<_Const>;
using _Res = invoke_result_t<__maybe_const_t<_Const, _Fp>&,
range_reference_t<_Base>>;
if constexpr (is_lvalue_reference_v<_Res>)
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3798. Rvalue reference and iterator_category
if constexpr (is_reference_v<_Res>)
{
using _Cat
= typename iterator_traits<iterator_t<_Base>>::iterator_category;
@ -5047,7 +5049,9 @@ namespace views::__adaptor
using __detail::__range_iter_cat;
using _Res = invoke_result_t<__maybe_const_t<_Const, _Fp>&,
range_reference_t<__maybe_const_t<_Const, _Vs>>...>;
if constexpr (!is_lvalue_reference_v<_Res>)
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3798. Rvalue reference and iterator_category
if constexpr (!is_reference_v<_Res>)
return input_iterator_tag{};
else if constexpr ((derived_from<__range_iter_cat<_Vs, _Const>,
random_access_iterator_tag> && ...))
@ -5820,7 +5824,9 @@ namespace views::__adaptor
using _Res = invoke_result_t<__unarize<__maybe_const_t<_Const, _Fp>&, _Nm>,
range_reference_t<_Base>>;
using _Cat = typename iterator_traits<iterator_t<_Base>>::iterator_category;
if constexpr (!is_lvalue_reference_v<_Res>)
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3798. Rvalue reference and iterator_category
if constexpr (!is_reference_v<_Res>)
return input_iterator_tag{};
else if constexpr (derived_from<_Cat, random_access_iterator_tag>)
return random_access_iterator_tag{};
@ -7228,8 +7234,10 @@ namespace views::__adaptor
using _OuterCat = typename iterator_traits<_OuterIter>::iterator_category;
using _InnerCat = typename iterator_traits<_InnerIter>::iterator_category;
using _PatternCat = typename iterator_traits<_PatternIter>::iterator_category;
if constexpr (!is_lvalue_reference_v<common_reference_t<iter_reference_t<_InnerIter>,
iter_reference_t<_PatternIter>>>)
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3798. Rvalue reference and iterator_category
if constexpr (!is_reference_v<common_reference_t<iter_reference_t<_InnerIter>,
iter_reference_t<_PatternIter>>>)
return input_iterator_tag{};
else if constexpr (derived_from<_OuterCat, bidirectional_iterator_tag>
&& derived_from<_InnerCat, bidirectional_iterator_tag>

16
libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
View File

@ -214,6 +214,21 @@ test10()
static_assert(std::same_as<cat, std::random_access_iterator_tag>);
}
void
test11()
{
struct MoveIt {
int&& operator()(int& i) const { return std::move(i); }
};
int x[] {2, 4};
auto xform = x | views::transform(MoveIt{});
using iterator = decltype(xform.begin());
// LWG 3798. Rvalue reference and iterator_category
using cat = std::iterator_traits<iterator>::iterator_category;
static_assert(std::same_as<cat, std::random_access_iterator_tag>);
}
int
main()
{
@ -227,4 +242,5 @@ main()
test08();
test09();
test10();
test11();
}