[libc++] Fix backdeployment annotations for std::filesystem

[ldionne]

Summary

In 1fa27f2a10e8, we made <filesystem>'s iterator types model concepts
from <ranges>, but we forgot to add the appropriate availability
annotations. This broke back-deployment to platforms that don't have
<filesystem> for which we have availability annotations.

For some reason, this wasn't caught by our back-deployment CI.
I believe this is due to the fact that we use a slightly older
compiler in the CI, and perhaps that compiler does not honour
our #pragma clang attribute push properly.

[jloser]

LGTM. Thanks for fixing this! I wish it could have been caught by CI when it was introduced, so that's room for future improvement.

Do we need to do _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH and corresponding _LIBCPP_AVAILABILITY_FILESYSTEM_POP around these template specializations to workaround https://bugs.llvm.org/show_bug.cgi?id=41078? I think the answer is "No", but wanted to confirm. :)

[ldionne]

In D114456#3149368, @jloser wrote:

LGTM. Thanks for fixing this! I wish it could have been caught by CI when it was introduced, so that's room for future improvement.

Do we need to do _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH and corresponding _LIBCPP_AVAILABILITY_FILESYSTEM_POP around these template specializations to workaround https://bugs.llvm.org/show_bug.cgi?id=41078? I think the answer is "No", but wanted to confirm. :)

Nope, it doesn't seem necessary, perhaps because directory_iterator isn't a template. I'm not too sure.

libcxx/include/filesystem

 }
 
 _LIBCPP_AVAILABILITY_FILESYSTEM_POP
 
 _LIBCPP_END_NAMESPACE_FILESYSTEM
 
 #if !defined(_LIBCPP_HAS_NO_RANGES)
 template <>
+_LIBCPP_AVAILABILITY_FILESYSTEM
 inline constexpr bool _VSTD::ranges::enable_borrowed_range<_VSTD_FS::directory_iterator> = true;
 template <>
+_LIBCPP_AVAILABILITY_FILESYSTEM
 inline constexpr bool _VSTD::ranges::enable_borrowed_range<_VSTD_FS::recursive_directory_iterator> = true;
 
 template <>
+_LIBCPP_AVAILABILITY_FILESYSTEM
 inline constexpr bool _VSTD::ranges::enable_view<_VSTD_FS::directory_iterator> = true;
 template <>
+_LIBCPP_AVAILABILITY_FILESYSTEM
 inline constexpr bool _VSTD::ranges::enable_view<_VSTD_FS::recursive_directory_iterator> = true;
 #endif
 
 #endif // !_LIBCPP_CXX03_LANG
 
 _LIBCPP_POP_MACROS
 
 #endif // _LIBCPP_FILESYSTEM

libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_bidirectional_iterator.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class I>
 // concept __iterator_traits_detail::__cpp17_bidirectional_iterator;
 
 #include <iterator>
 
 #include <array>
 #include <deque>
 #ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY

libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_forward_iterator.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class I>
 // concept __iterator_traits_detail::__cpp17_forward_iterator;
 
 #include <iterator>
 
 #include <array>
 #include <deque>
 #ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY

libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_input_iterator.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class I>
 // concept __iterator_traits_detail::__cpp17_input_iterator;
 
 #include <iterator>
 
 #include <array>
 #include <deque>
 #ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY

libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_iterator.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class I>
 // concept __iterator_traits_detail::__cpp17_iterator;
 
 #include <iterator>
 
 #include <array>
 #include <deque>
 #ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY

libcxx/test/libcxx/iterators/iterator.requirements/iterator.assoc.types/iterator.traits/legacy_random_access_iterator.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class I>
 // concept __iterator_traits_detail::__cpp17_random_access_iterator;
 
 #include <iterator>
 
 #include <array>
 #include <deque>
 #ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY

libcxx/test/std/iterators/iterator.primitives/iterator.traits/cxx20_iterator_traits.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
 
+// This test uses iterator types from std::filesystem, which were introduced in macOS 10.15.
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 // template<class T>
 // struct iterator_traits;
 
 #include <iterator>
 
 #include <array>
 #include <concepts>
 #include <cstddef>