[libc++] Add _ITER_CONCEPT and _ITER_TRAITS implementations from C++20
These traits are currently unused because we don't implement ranges.
However, their addition is part of ongoing work to allow libc++
to optimize on user-provided contiguous iterators.
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 6624fcba43be88fd357c74435a4d6462858c8fed
diff --git a/include/iterator b/include/iterator
index 6a9a082..13329e1 100644
--- a/include/iterator
+++ b/include/iterator
@@ -434,6 +434,8 @@
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
+template <class _Iter>
+struct _LIBCPP_TEMPLATE_VIS iterator_traits;
struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {};
@@ -446,6 +448,52 @@
struct _LIBCPP_TEMPLATE_VIS contiguous_iterator_tag: public random_access_iterator_tag { };
#endif
+template <class _Iter>
+struct __iter_traits_cache {
+ using type = _If<
+ __is_primary_template<iterator_traits<_Iter> >::value,
+ _Iter,
+ iterator_traits<_Iter>
+ >;
+};
+template <class _Iter>
+using _ITER_TRAITS = typename __iter_traits_cache<_Iter>::type;
+
+struct __iter_concept_concept_test {
+ template <class _Iter>
+ using _Apply = typename _ITER_TRAITS<_Iter>::iterator_concept;
+};
+struct __iter_concept_category_test {
+ template <class _Iter>
+ using _Apply = typename _ITER_TRAITS<_Iter>::iterator_category;
+};
+struct __iter_concept_random_fallback {
+ template <class _Iter>
+ using _Apply = _EnableIf<
+ __is_primary_template<iterator_traits<_Iter> >::value,
+ random_access_iterator_tag
+ >;
+};
+
+template <class _Iter, class _Tester> struct __test_iter_concept
+ : _IsValidExpansion<_Tester::template _Apply, _Iter>,
+ _Tester
+{
+};
+
+template <class _Iter>
+struct __iter_concept_cache {
+ using type = _Or<
+ __test_iter_concept<_Iter, __iter_concept_concept_test>,
+ __test_iter_concept<_Iter, __iter_concept_category_test>,
+ __test_iter_concept<_Iter, __iter_concept_random_fallback>
+ >;
+};
+
+template <class _Iter>
+using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type::template _Apply<_Iter>;
+
+
template <class _Tp>
struct __has_iterator_typedefs
{
@@ -505,7 +553,10 @@
template <class _Iter>
struct _LIBCPP_TEMPLATE_VIS iterator_traits
- : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {};
+ : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {
+
+ using __primary_template = iterator_traits;
+};
template<class _Tp>
struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
diff --git a/include/type_traits b/include/type_traits
index cd0aff9..c0c3934 100644
--- a/include/type_traits
+++ b/include/type_traits
@@ -525,6 +525,7 @@
template <class _Tp, bool>
struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
+
template <bool _Bp, class _If, class _Then>
struct _LIBCPP_TEMPLATE_VIS conditional {typedef _If type;};
template <class _If, class _Then>
@@ -570,6 +571,16 @@
#endif
>;
+
+template <class _Tp>
+using __test_for_primary_template = _EnableIf<
+ _IsSame<_Tp, typename _Tp::__primary_template>::value
+ >;
+template <class _Tp>
+using __is_primary_template = _IsValidExpansion<
+ __test_for_primary_template, _Tp
+ >;
+
// addressof
#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF