[libc++] Implement `operator==` for `filesystem::space_info`

[avogelsgesang]

Summary

Implements part of P1614R2 "The Mothership has Landed"

[avogelsgesang]

need to update based on comments in https://reviews.llvm.org/D130852

[avogelsgesang]

update based on first feedback on https://reviews.llvm.org/D130852

[avogelsgesang]

Fix test cases

[avogelsgesang]

rebase on D130855

[avogelsgesang]

update synopsis

[avogelsgesang]

Add missing _LIBCPP_HIDE_FROM_ABI

[Mordante]

LGTM, except for the missing constexpr test. I want to see that before approving.

libcxx/test/std/input.output/filesystems/fs.filesystem.synopsis/space_info.pass.cpp

28

Please also test as constexpr since the defaulted is a constexpr function. (http://eel.is/c++draft/class.compare.default#4)

[avogelsgesang]

Add constexpr test

[avogelsgesang]

Remove debug include

[Mordante]

LGTM!

libcxx/docs/Status/SpaceshipProjects.csv

 | chrono::year_month
 | chrono::year_month_day
 | chrono::year_month_day_last",None,Mark de Wever,|Complete|
 "| `[time.zone.nonmembers] <https://wg21.link/time.zone.nonmembers>`_
 | `[time.zone.leap.nonmembers] <https://wg21.link/time.zone.leap.nonmembers>`_
 | `[time.zone.link.nonmembers] <https://wg21.link/time.zone.link.nonmembers>`_","| chrono::time_zone
 | chrono::leap_second
 | chrono::time_zone_link",A ``<chrono>`` implementation,Unassigned,|Not Started|
+| `[fs.filesystem.syn] <https://wg21.link/fs.filesystem.syn>`_,| filesystem::space_info,None,Adrian Vogelsgesang,|Done|
 | `[fs.path.nonmember] <https://wg21.link/fs.path.nonmember>`_,| filesystem::path,None,Unassigned,|Not Started|
 | `[fs.dir.entry.obs] <https://wg21.link/fs.dir.entry.obs>`_,| filesystem::directory_entry,None,Unassigned,|Not Started|
 | `[re.submatch.op] <https://wg21.link/re.submatch.op>`_,| sub_match,None,Unassigned,|Not Started|
 | `[thread.thread.id] <https://wg21.link/thread.thread.id>`_,| thread::id,None,Unassigned,|Not Started|

libcxx/include/__filesystem/space_info.h

 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
 _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH
 
 struct _LIBCPP_TYPE_VIS space_info {
   uintmax_t capacity;
   uintmax_t free;
   uintmax_t available;
+
+#  if _LIBCPP_STD_VER > 17
+  friend bool operator==(const space_info&, const space_info&) = default;
+#  endif
 };
 
 _LIBCPP_AVAILABILITY_FILESYSTEM_POP
 
 _LIBCPP_END_NAMESPACE_FILESYSTEM
 
 #endif // _LIBCPP_CXX03_LANG
 
 #endif // _LIBCPP___FILESYSTEM_SPACE_INFO_H

libcxx/test/std/input.output/filesystems/fs.filesystem.synopsis/space_info.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
+
+// <filesystem>
+
+// friend bool operator==(const space_info&, const space_info&);
+
+#include "filesystem_include.h"
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+using namespace fs;
+
+int main(int, char**) {
+  using space_info = std::filesystem::space_info;
+
+  AssertEqualityAreNoexcept<space_info>();
+  AssertEqualityReturnBool<space_info>();
+
+  assert(testEquality(space_info{1, 2, 3}, space_info{1, 2, 3}, true));
+  assert(testEquality(space_info{0, 2, 3}, space_info{1, 2, 3}, false));
+  assert(testEquality(space_info{1, 0, 3}, space_info{1, 2, 3}, false));
+  assert(testEquality(space_info{1, 2, 0}, space_info{1, 2, 3}, false));
+
+  return 0;
+}