[libc++] Add range_size_t

[ldionne]

Update with review link.

[• Quuxplusone]

LGTM mod comments.

libcxx/include/__ranges/concepts.h

73

This is actually from section [range.range], not [range.sized]. I doubt we care.

libcxx/include/ranges

38–40

No, T was correct. https://eel.is/c++draft/ranges#syn
It's noteworthy that iterator_t is not constrained — class T is correct, not range T. I don't know why.

libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp

29

Please add SFINAE-friendliness tests. I recommend replacing this whole file with:

template<class T>
concept has_size_t = requires { typename std::ranges::range_size_t<T>; };

struct A { int *begin(); int *end(); short size(); };
static_assert(std::same_as<std::ranges::range_size_t<A>, short>);
static_assert(std::same_as<std::ranges::range_size_t<A&>, short>);
static_assert(std::same_as<std::ranges::range_size_t<A&&>, short>);
static_assert(!has_size_t<const A>);
static_assert(!has_size_t<const A&>);
static_assert(!has_size_t<const A&&>);

struct B { int *begin(); int *end(); };
static_assert(std::same_as<std::ranges::range_size_t<B>, std::size_t>);
static_assert(std::same_as<std::ranges::range_size_t<B&>, std::size_t>);
static_assert(std::same_as<std::ranges::range_size_t<B&&>, std::size_t>);
static_assert(!has_size_t<const B>);
static_assert(!has_size_t<const B&>);
static_assert(!has_size_t<const B&&>);

struct C { bidirectional_iterator<int*> begin(); bidirectional_iterator<int*> end(); };
static_assert(!has_size_t<C>);

[Mordante]

LGTM, modulo comment.

libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp

29

+1

[ldionne]

libcxx/include/__ranges/concepts.h

73

Yeah, I couldn't put it in the section above cause it needs sized_range to be defined. I won't add another comment, that would just be confusing IMO.

[ldionne]

Address review comments (thanks!)

libcxx/docs/Status/RangesPaper.csv

 | `ranges::data <https://llvm.org/D101476>`_
 | ranges::cdata",[iterator.concepts],Christopher Di Bella and Zoe Carver,In progress
 `[range.range] <http://wg21.link/range.range>`_,"| `ranges::range <https://llvm.org/D100269>`_
 | `ranges::borrowed_range <https://llvm.org/D102426>`_
 | `ranges::enable_borrowed_range <https://llvm.org/D90999>`_
 | `ranges::iterator_t <https://llvm.org/D100255>`_
 | `ranges::sentinel_t <https://llvm.org/D100269>`_
 | `ranges::range_difference_t <https://llvm.org/D100269>`_
-| ranges::range_size_t
+| `ranges::range_size_t <https://llvm.org/TODO>`_
 | `ranges::range_value_t <https://llvm.org/D100269>`_
 | `ranges::range_reference_t <https://llvm.org/D100269>`_
-| `ranges::range_rvalue_reference_t <https://llvm.org/D100269>`_",[range.access],Christopher Di Bella,In progress
+| `ranges::range_rvalue_reference_t <https://llvm.org/D100269>`_",[range.access],Christopher Di Bella,✅
 `[range.sized] <http://wg21.link/range.sized>`_,"| `ranges::sized_range <https://llvm.org/D102434>`_
 | `ranges::disable_sized_range <https://llvm.org/D102434>`_","| [range.primitives]
 | [range.range]",Christopher Di Bella,✅
 `[range.view] <http://wg21.link/range.view>`_,"| `ranges::enable_view <https://llvm.org/D101547>`_
 | `ranges::view_base <https://llvm.org/D101547>`_
 | `ranges::view <https://llvm.org/D101547>`_",[range.range],Louis Dionne,✅
 `[range.refinements] <http://wg21.link/range.refinements>`_,"| ranges::output_range
 | `ranges::input_range <https://llvm.org/D100271>`_

libcxx/include/__ranges/concepts.h

namespace ranges {
 
   template <range _Rp>
   using range_rvalue_reference_t = iter_rvalue_reference_t<iterator_t<_Rp> >;
 
   // [range.sized]
   template <class _Tp>
   concept sized_range = range<_Tp> && requires(_Tp& __t) { ranges::size(__t); };
 
+  template<sized_range _Rp>
+  using range_size_t = decltype(ranges::size(declval<_Rp&>()));
+
   // `disable_sized_range` defined in `<__ranges/size.h>`
 
   // [range.view], views
 
   // `enable_view` defined in <__ranges/enable_view.h>
   // `view_base` defined in <__ranges/enable_view.h>
 
   template <class _Tp>

libcxx/include/ranges

namespace std::ranges {
 
   // [range.range], ranges
   template<class T>
     concept range = see below;
 
   template<class T>
     inline constexpr bool enable_borrowed_range = false;
 
-  template<class T>
-    using iterator_t = decltype(ranges::begin(declval<T&>()));
-  template<class T>
-    using iterator_t = decltype(ranges::begin(declval<T&>()));
+  template<class R>
+    using iterator_t = decltype(ranges::begin(declval<R&>()));
   template<range R>
     using sentinel_t = decltype(ranges::end(declval<R&>()));
   template<range R>
     using range_difference_t = iter_difference_t<iterator_t<R>>;
+  template<sized_range R>
+    using range_size_t = decltype(ranges::size(declval<R&>()));
   template<range R>
     using range_value_t = iter_value_t<iterator_t<R>>;
   template<range R>
     using range_reference_t = iter_reference_t<iterator_t<R>>;
   template<range R>
     using range_rvalue_reference_t = iter_rvalue_reference_t<iterator_t<R>>;
 
   // [range.sized], sized ranges

libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+// UNSUPPORTED: gcc-10
+
+// template<sized_range R>
+// using range_size_t = decltype(ranges::size(declval<R&>()));
+
+#include <ranges>
+#include <concepts>
+
+#include "test_iterators.h"
+#include "test_range.h"
+
+struct Range {
+    cpp17_input_iterator<int*> begin();
+    sentinel end();
+    short size() const;
+};
+
+static_assert(std::same_as<std::ranges::range_size_t<Range>, short>);