[libc++][ranges] implement `std::views::elements_view`
`subrange` is also a `tuple-like`. To avoid the add entire `subrange` dependencies to `tuple-like`, we need forward declaration of `subrange`. However, the class template constraints of `subrange` currently requires `__iterator/concepts.h`, which requires `<concepts>`. The problem is that currently `tuple-like` is used in several different places, including libc++ extension for pair constructors. we don't want to add `<concepts>` to pair and other stuff. So this change also created several small headers that `subrange`'s declaration needed inside `__iterator/concepts/`
Differential Revision: https://reviews.llvm.org/D136268
NOKEYCHECK=True
GitOrigin-RevId: 94461822c75d5080bf648f86552f7a59b76905c9
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 40c5951..6f08d95 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -66,6 +66,7 @@
- P0415R1 - ``constexpr`` for ``std::complex``
- P1208R6 - ``std::source_location``
- P0323R12 - ``std::expected``
+- P1035R7 - Input Range Adaptors
Improvements and New Features
-----------------------------
diff --git a/docs/Status/Cxx20Issues.csv b/docs/Status/Cxx20Issues.csv
index d023df6..48bc936 100644
--- a/docs/Status/Cxx20Issues.csv
+++ b/docs/Status/Cxx20Issues.csv
@@ -281,7 +281,7 @@
"`3373 <https://wg21.link/LWG3373>`__","``{to,from}_chars_result``\ and ``format_to_n_result``\ need the ""we really mean what we say"" wording","Prague","|Complete|","14.0","|format|"
"`3374 <https://wg21.link/LWG3374>`__","P0653 + P1006 should have made the other ``std::to_address``\ overload ``constexpr``\ ","Prague","|Complete|","12.0"
"`3375 <https://wg21.link/LWG3375>`__","``decay``\ in ``viewable_range``\ should be ``remove_cvref``\ ","Prague","|Complete|","15.0","|ranges|"
-"`3377 <https://wg21.link/LWG3377>`__","``elements_view::iterator``\ befriends a specialization of itself","Prague","","","|ranges|"
+"`3377 <https://wg21.link/LWG3377>`__","``elements_view::iterator``\ befriends a specialization of itself","Prague","|Nothing To Do|","","|ranges|"
"`3379 <https://wg21.link/LWG3379>`__","""``safe``\ "" in several library names is misleading","Prague","|Complete|","15.0","|ranges|"
"`3380 <https://wg21.link/LWG3380>`__","``common_type``\ and comparison categories","Prague","|Complete|","15.0","|spaceship|"
"`3381 <https://wg21.link/LWG3381>`__","``begin``\ and ``data``\ must agree for ``contiguous_range``\ ","Prague","|Nothing To Do|","","|ranges|"
diff --git a/docs/Status/Cxx20Papers.csv b/docs/Status/Cxx20Papers.csv
index d03017b..10fde39 100644
--- a/docs/Status/Cxx20Papers.csv
+++ b/docs/Status/Cxx20Papers.csv
@@ -108,7 +108,7 @@
"`P0784R7 <https://wg21.link/P0784R7>`__","CWG","More constexpr containers","Cologne","|Complete|","12.0"
"`P0980R1 <https://wg21.link/P0980R1>`__","LWG","Making std::string constexpr","Cologne","|Complete|","15.0"
"`P1004R2 <https://wg21.link/P1004R2>`__","LWG","Making std::vector constexpr","Cologne","|Complete|","15.0"
-"`P1035R7 <https://wg21.link/P1035R7>`__","LWG","Input Range Adaptors (mostly implemented, TODO: elements_view)","Cologne","|In Progress|","","|ranges|"
+"`P1035R7 <https://wg21.link/P1035R7>`__","LWG","Input Range Adaptors","Cologne","|Complete|","16.0","|ranges|"
"`P1065R2 <https://wg21.link/P1065R2>`__","LWG","Constexpr INVOKE","Cologne","|Complete|","12.0"
"`P1135R6 <https://wg21.link/P1135R6>`__","LWG","The C++20 Synchronization Library","Cologne","|Complete|","11.0"
"`P1207R4 <https://wg21.link/P1207R4>`__","LWG","Movability of Single-pass Iterators","Cologne","|Complete|","15.0","|ranges|"
@@ -182,7 +182,7 @@
"`P1981R0 <https://wg21.link/P1981R0>`__","LWG","Rename leap to leap_second","Prague","* *",""
"`P1982R0 <https://wg21.link/P1982R0>`__","LWG","Rename link to time_zone_link","Prague","* *",""
"`P1983R0 <https://wg21.link/P1983R0>`__","LWG","Wording for GB301, US296, US292, US291, and US283","Prague","|Complete|","15.0","|ranges|"
-"`P1994R1 <https://wg21.link/P1994R1>`__","LWG","elements_view needs its own sentinel","Prague","* *","","|ranges|"
+"`P1994R1 <https://wg21.link/P1994R1>`__","LWG","elements_view needs its own sentinel","Prague","Complete","16.0","|ranges|"
"`P2002R1 <https://wg21.link/P2002R1>`__","CWG","Defaulted comparison specification cleanups","Prague","* *",""
"`P2045R1 <https://wg21.link/P2045R1>`__","LWG","Missing Mandates for the standard library","Prague","* *",""
"`P2085R0 <https://wg21.link/P2085R0>`__","CWG","Consistent defaulted comparisons","Prague","* *",""
diff --git a/docs/Status/Cxx2bIssues.csv b/docs/Status/Cxx2bIssues.csv
index 2acfc80..e92cfc3 100644
--- a/docs/Status/Cxx2bIssues.csv
+++ b/docs/Status/Cxx2bIssues.csv
@@ -22,7 +22,7 @@
"`3403 <https://wg21.link/LWG3403>`__","Domain of ``ranges::ssize(E)`` doesn't ``match ranges::size(E)``","November 2020","","","|ranges|"
"`3404 <https://wg21.link/LWG3404>`__","Finish removing subrange's conversions from pair-like","November 2020","","","|ranges|"
"`3405 <https://wg21.link/LWG3405>`__","``common_view``'s converting constructor is bad, too","November 2020","|Complete|","14.0","|ranges|"
-"`3406 <https://wg21.link/LWG3406>`__","``elements_view::begin()`` and ``elements_view::end()`` have incompatible constraints","November 2020","","","|ranges|"
+"`3406 <https://wg21.link/LWG3406>`__","``elements_view::begin()`` and ``elements_view::end()`` have incompatible constraints","November 2020","|Complete|","16.0","|ranges|"
"`3419 <https://wg21.link/LWG3419>`__","[algorithms.requirements]/15 doesn't reserve as many rights as it intends to","November 2020","|Nothing To Do|",""
"`3420 <https://wg21.link/LWG3420>`__","cpp17-iterator should check that the type looks like an iterator first","November 2020","|Complete|","14.0","|ranges|"
"`3421 <https://wg21.link/LWG3421>`__","Imperfect ADL emulation for boolean-testable","November 2020","|Nothing To Do|","","|ranges|"
@@ -53,11 +53,11 @@
"`3391 <https://wg21.link/LWG3391>`__","Problems with ``counted_iterator``/``move_iterator::base() const &``","February 2021","","","|ranges|"
"`3433 <https://wg21.link/LWG3433>`__","``subrange::advance(n)`` has UB when ``n < 0``","February 2021","|Complete|","14.0","|ranges|"
"`3490 <https://wg21.link/LWG3490>`__","``ranges::drop_while_view::begin()`` is missing a precondition","February 2021","|Nothing To Do|","","|ranges|"
-"`3492 <https://wg21.link/LWG3492>`__","Minimal improvements to ``elements_view::iterator``","February 2021","","","|ranges|"
+"`3492 <https://wg21.link/LWG3492>`__","Minimal improvements to ``elements_view::iterator``","February 2021","|Complete|","16.0","|ranges|"
"`3494 <https://wg21.link/LWG3494>`__","Allow ranges to be conditionally borrowed","February 2021","Superseded by `P2017R1 <https://wg21.link/P2017R1>`__","","|ranges|"
"`3495 <https://wg21.link/LWG3495>`__","``constexpr launder`` makes pointers to inactive members of unions usable","February 2021","|Nothing To Do|",""
"`3500 <https://wg21.link/LWG3500>`__","``join_view::iterator::operator->()`` is bogus","February 2021","|Complete|","14.0","|ranges|"
-"`3502 <https://wg21.link/LWG3502>`__","``elements_view`` should not be allowed to return dangling reference","February 2021","","","|ranges|"
+"`3502 <https://wg21.link/LWG3502>`__","``elements_view`` should not be allowed to return dangling reference","February 2021","|Complete|","16.0","|ranges|"
"`3505 <https://wg21.link/LWG3505>`__","``split_view::outer-iterator::operator++`` misspecified","February 2021","","","|ranges|"
"","","","","",""
`2774 <https://wg21.link/LWG2774>`__,"``std::function`` construction vs assignment","June 2021","",""
diff --git a/docs/Status/SpaceshipProjects.csv b/docs/Status/SpaceshipProjects.csv
index dec2a89..f732ec7 100644
--- a/docs/Status/SpaceshipProjects.csv
+++ b/docs/Status/SpaceshipProjects.csv
@@ -51,7 +51,7 @@
| `[counted.iter.cmp] <https://wg21.link/counted.iter.cmp>`_,| counted_iterator,None,Unassigned,|Not Started|
| `[range.iota.iterator] <https://wg21.link/range.iota.iterator>`_,| `ranges::iota_view::iterator <https://reviews.llvm.org/D110774>`_,[concepts.cmp],Arthur O'Dwyer,|Complete|
| `[range.transform.iterator] <https://wg21.link/range.transform.iterator>`_,| `ranges::transform_view::iterator <https://reviews.llvm.org/D110774>`_,[concepts.cmp],Arthur O'Dwyer,|Complete|
-| `[range.elements.iterator] <https://wg21.link/range.elements.iterator>`_,| ranges::elements_view::iterator,[concepts.cmp],Unassigned,|Not Started|
+| `[range.elements.iterator] <https://wg21.link/range.elements.iterator>`_,| ranges::elements_view::iterator,[concepts.cmp],Hui Xie,|Complete|
| `[time.duration.comparisons] <https://wg21.link/time.duration.comparisons>`_, "chrono::duration", None, Mark de Wever, |Not Started|
| `[time.point.comparisons] <https://wg21.link/time.point.comparisons>`_, "chrono::time_point", None, Mark de Wever, |Not Started|
"| `[time.cal.day.nonmembers] <https://wg21.link/time.cal.day.nonmembers>`_