Skip to content

[libc++] Use __detected_or_t to implement __has_iterator_{category,concept}_convertible_to #124456

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Mar 26, 2025
Merged

[libc++] Use __detected_or_t to implement __has_iterator_{category,concept}_convertible_to #124456

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
43 changes: 11 additions & 32 deletions libcxx/include/__iterator/iterator_traits.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <__iterator/readable_traits.h>
#include <__type_traits/common_reference.h>
#include <__type_traits/conditional.h>
#include <__type_traits/detected_or.h>
#include <__type_traits/disjunction.h>
#include <__type_traits/enable_if.h>
#include <__type_traits/integral_constant.h>
Expand All @@ -32,6 +33,7 @@
#include <__type_traits/is_primary_template.h>
#include <__type_traits/is_reference.h>
#include <__type_traits/is_valid_expansion.h>
#include <__type_traits/nat.h>
#include <__type_traits/remove_const.h>
#include <__type_traits/remove_cv.h>
#include <__type_traits/remove_cvref.h>
Expand Down Expand Up @@ -126,30 +128,6 @@ struct __has_iterator_typedefs {
static const bool value = decltype(__test<_Tp>(nullptr, nullptr, nullptr, nullptr, nullptr))::value;
};

template <class _Tp>
struct __has_iterator_category {
private:
template <class _Up>
static false_type __test(...);
template <class _Up>
static true_type __test(typename _Up::iterator_category* = nullptr);

public:
static const bool value = decltype(__test<_Tp>(nullptr))::value;
};

template <class _Tp>
struct __has_iterator_concept {
private:
template <class _Up>
static false_type __test(...);
template <class _Up>
static true_type __test(typename _Up::iterator_concept* = nullptr);

public:
static const bool value = decltype(__test<_Tp>(nullptr))::value;
};

#if _LIBCPP_STD_VER >= 20

// The `cpp17-*-iterator` exposition-only concepts have very similar names to the `Cpp17*Iterator` named requirements
Expand Down Expand Up @@ -417,18 +395,19 @@ struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*> {
#endif
};

template <class _Tp, class _Up, bool = __has_iterator_category<iterator_traits<_Tp> >::value>
struct __has_iterator_category_convertible_to : is_convertible<typename iterator_traits<_Tp>::iterator_category, _Up> {
};
template <class _Tp>
using __iterator_category _LIBCPP_NODEBUG = typename _Tp::iterator_category;

template <class _Tp, class _Up>
struct __has_iterator_category_convertible_to<_Tp, _Up, false> : false_type {};
template <class _Tp>
using __iterator_concept _LIBCPP_NODEBUG = typename _Tp::iterator_concept;

template <class _Tp, class _Up, bool = __has_iterator_concept<_Tp>::value>
struct __has_iterator_concept_convertible_to : is_convertible<typename _Tp::iterator_concept, _Up> {};
template <class _Tp, class _Up>
using __has_iterator_category_convertible_to _LIBCPP_NODEBUG =
is_convertible<__detected_or_t<__nat, __iterator_category, iterator_traits<_Tp> >, _Up>;

template <class _Tp, class _Up>
struct __has_iterator_concept_convertible_to<_Tp, _Up, false> : false_type {};
using __has_iterator_concept_convertible_to _LIBCPP_NODEBUG =
is_convertible<__detected_or_t<__nat, __iterator_concept, _Tp>, _Up>;

template <class _Tp>
using __has_input_iterator_category _LIBCPP_NODEBUG = __has_iterator_category_convertible_to<_Tp, input_iterator_tag>;
Expand Down
6 changes: 5 additions & 1 deletion libcxx/include/module.modulemap
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -418,7 +418,10 @@ module std [system] {
module copy_backward { header "__algorithm/copy_backward.h" }
module copy_if { header "__algorithm/copy_if.h" }
module copy_move_common { header "__algorithm/copy_move_common.h" }
module copy_n { header "__algorithm/copy_n.h" }
module copy_n {
header "__algorithm/copy_n.h"
export std.iterator_traits
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Why is that export necessary?

Copy link
Contributor Author

@philnik777 philnik777 Mar 26, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I can't remember anymore why, but I'm quite certain I've looked into this and it made some amount of sense.

}
module copy { header "__algorithm/copy.h" }
module count_if { header "__algorithm/count_if.h" }
module count { header "__algorithm/count.h" }
Expand Down Expand Up @@ -1471,6 +1474,7 @@ module std [system] {
module iterator_traits {
header "__iterator/iterator_traits.h"
export std_core.type_traits.integral_constant
export std_core.type_traits.is_convertible
}
module iterator_with_data { header "__iterator/iterator_with_data.h" }
module iterator { header "__iterator/iterator.h" }
Expand Down
Loading