[libcxx-commits] [libcxx] d9caea1 - [libc++][ranges] LWG3564: `transform_view::iterator<true>::value_type` and `iterator_category` should use `const F&` (#91816)
via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Aug 12 10:30:50 PDT 2024
Author: Xiaoyang Liu
Date: 2024-08-12T19:30:47+02:00
New Revision: d9caea18f946390e0b458471cdc3e3252099c1cf
URL: https://github.com/llvm/llvm-project/commit/d9caea18f946390e0b458471cdc3e3252099c1cf
DIFF: https://github.com/llvm/llvm-project/commit/d9caea18f946390e0b458471cdc3e3252099c1cf.diff
LOG: [libc++][ranges] LWG3564: `transform_view::iterator<true>::value_type` and `iterator_category` should use `const F&` (#91816)
## Introduction
This patch implements LWG3564:
`transform_view::iterator<true>::value_type` and `iterator_category`
should use `const F&`.
`transform_view`'s iterator currently obtained from a `const
transform_view` invoke the transformation function as `const`, but the
`value_type` and `iterator_category` determination uses non-`const`
`F&`.
## Reference
-
[[range.transform.iterator]](https://eel.is/c++draft/range.transform.iterator)
- [LWG3564](https://cplusplus.github.io/LWG/issue3564)
Added:
Modified:
libcxx/docs/Status/Cxx23Issues.csv
libcxx/include/__ranges/transform_view.h
libcxx/test/std/ranges/range.adaptors/range.transform/iterator/types.pass.cpp
libcxx/test/std/ranges/range.adaptors/range.transform/types.h
Removed:
################################################################################
diff --git a/libcxx/docs/Status/Cxx23Issues.csv b/libcxx/docs/Status/Cxx23Issues.csv
index c4c6a855cc517b..b6381f86323dbd 100644
--- a/libcxx/docs/Status/Cxx23Issues.csv
+++ b/libcxx/docs/Status/Cxx23Issues.csv
@@ -159,7 +159,7 @@
"`LWG3660 <https://wg21.link/LWG3660>`__","``iterator_traits<common_iterator>::pointer`` should conform to ยง[iterator.traits]","February 2022","|Complete|","14.0","|ranges|"
"`LWG3661 <https://wg21.link/LWG3661>`__","``constinit atomic<shared_ptr<T>> a(nullptr);`` should work","February 2022","","",""
"","","","","",""
-"`LWG3564 <https://wg21.link/LWG3564>`__","``transform_view::iterator<true>::value_type`` and ``iterator_category`` should use ``const F&``","July 2022","","","|ranges|"
+"`LWG3564 <https://wg21.link/LWG3564>`__","``transform_view::iterator<true>::value_type`` and ``iterator_category`` should use ``const F&``","July 2022","|Complete|","20.0","|ranges|"
"`LWG3617 <https://wg21.link/LWG3617>`__","``function``/``packaged_task`` deduction guides and deducing ``this``","July 2022","","",""
"`LWG3656 <https://wg21.link/LWG3656>`__","Inconsistent bit operations returning a count","July 2022","|Complete|","15.0",""
"`LWG3659 <https://wg21.link/LWG3659>`__","Consider ``ATOMIC_FLAG_INIT`` undeprecation","July 2022","|Complete|","15.0",""
diff --git a/libcxx/include/__ranges/transform_view.h b/libcxx/include/__ranges/transform_view.h
index bcce389c0e6809..686a2a8fe8c21e 100644
--- a/libcxx/include/__ranges/transform_view.h
+++ b/libcxx/include/__ranges/transform_view.h
@@ -173,7 +173,8 @@ template <input_range _View, copy_constructible _Fn>
# endif
requires __transform_view_constraints<_View, _Fn>
template <bool _Const>
-class transform_view<_View, _Fn>::__iterator : public __transform_view_iterator_category_base<_View, _Fn> {
+class transform_view<_View, _Fn>::__iterator
+ : public __transform_view_iterator_category_base<_View, __maybe_const<_Const, _Fn>> {
using _Parent = __maybe_const<_Const, transform_view>;
using _Base = __maybe_const<_Const, _View>;
@@ -190,7 +191,7 @@ class transform_view<_View, _Fn>::__iterator : public __transform_view_iterator_
iterator_t<_Base> __current_ = iterator_t<_Base>();
using iterator_concept = typename __transform_view_iterator_concept<_View>::type;
- using value_type = remove_cvref_t<invoke_result_t<_Fn&, range_reference_t<_Base>>>;
+ using value_type = remove_cvref_t<invoke_result_t<__maybe_const<_Const, _Fn>&, range_reference_t<_Base>>>;
using
diff erence_type = range_
diff erence_t<_Base>;
_LIBCPP_HIDE_FROM_ABI __iterator()
diff --git a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/types.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/types.pass.cpp
index 25d8936f4e4ebd..607b748ac3e4bd 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/types.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/types.pass.cpp
@@ -61,6 +61,22 @@ constexpr bool test() {
static_assert(std::same_as<typename TIter::value_type, int>);
static_assert(std::same_as<typename TIter::
diff erence_type, std::ptr
diff _t>);
}
+ {
+ // Member typedefs for random access iterator, LWG3564 mutable overload
+ using TView = std::ranges::transform_view<RandomAccessView, PlusOneMutableOverload>;
+ using TIter = std::ranges::iterator_t<TView>;
+ static_assert(std::same_as<typename TIter::iterator_concept, std::random_access_iterator_tag>);
+ static_assert(std::same_as<typename TIter::iterator_category, std::random_access_iterator_tag>);
+ static_assert(std::same_as<typename TIter::value_type, int>);
+ static_assert(std::same_as<typename TIter::
diff erence_type, std::ptr
diff _t>);
+
+ using CTIter = std::ranges::iterator_t<const TView>;
+ static_assert(std::same_as<typename CTIter::iterator_concept, std::random_access_iterator_tag>);
+ static_assert(std::same_as<typename CTIter::iterator_category,
+ std::input_iterator_tag>); // Note: this is now input_iterator_tag.
+ static_assert(std::same_as<typename CTIter::value_type, int>);
+ static_assert(std::same_as<typename CTIter::
diff erence_type, std::ptr
diff _t>);
+ }
{
// Member typedefs for bidirectional iterator.
using TView = std::ranges::transform_view<BidirectionalView, Increment>;
diff --git a/libcxx/test/std/ranges/range.adaptors/range.transform/types.h b/libcxx/test/std/ranges/range.adaptors/range.transform/types.h
index cc5679f229de25..e94e7dfcdaeb7e 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.transform/types.h
+++ b/libcxx/test/std/ranges/range.adaptors/range.transform/types.h
@@ -131,6 +131,11 @@ struct PlusOne {
constexpr int operator()(int x) const { return x + 1; }
};
+struct PlusOneMutableOverload {
+ constexpr int operator()(int x) const { return x + 1; }
+ constexpr int& operator()(int& x) { return ++x; }
+};
+
struct Increment {
constexpr int& operator()(int& x) { return ++x; }
};
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