[libc++] [ranges] Permit std::mergeable and std::sortable with HAS_NO_INCOMPLETE_RANGES

[• Quuxplusone]

Summary

This follows the general direction of D118736 that _LIBCPP_HAS_NO_INCOMPLETE_RANGES does *not* guard anything outside of the std::ranges:: namespace itself. This means we must permit ranges::less etc. in no-ranges mode; that seems fine to me.

I believe this doesn't need to be merged to release/14.x, unless @ldionne you want to also merge eea3d90af181fdb66e583af53401e80ddfcc8cd1 and 8e979460bb27610d574733ca5b75afae0cdfb3c9 to release/14.x? (Again, the only logic to that would be so that we could brag that a sensible, non-arbitrary subset was implemented in libc++14.)

[Mordante]

Based on the direction in D118736 this LGTM!
I agree there's no need to backport it to LLVM 14.

libcxx/include/__functional/ranges_operations.h

 #include <concepts>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#if !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 namespace ranges {
 
 struct equal_to {
   template <class _Tp, class _Up>
   requires equality_comparable_with<_Tp, _Up>
   [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
       noexcept(noexcept(bool(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u)))) {
[[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
       noexcept(noexcept(bool(!(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u))))) {
     return !(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u));
   }
 
   using is_transparent = void;
 };
 
 } // namespace ranges
-#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+
+#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___FUNCTIONAL_RANGES_OPERATIONS_H

libcxx/include/__iterator/mergeable.h

 #include <__iterator/projected.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#if !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 template <class _Input1, class _Input2, class _Output,
           class _Comp = ranges::less, class _Proj1 = identity, class _Proj2 = identity>
 concept mergeable =
     input_iterator<_Input1> &&
     input_iterator<_Input2> &&
     weakly_incrementable<_Output> &&
     indirectly_copyable<_Input1, _Output> &&
     indirectly_copyable<_Input2, _Output> &&
     indirect_strict_weak_order<_Comp, projected<_Input1, _Proj1>, projected<_Input2, _Proj2>>;
 
-#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ITERATOR_MERGEABLE_H

libcxx/include/__iterator/sortable.h

 #include <__iterator/projected.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#if !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 template <class _Iter, class _Comp = ranges::less, class _Proj = identity>
 concept sortable =
   permutable<_Iter> &&
   indirect_strict_weak_order<_Comp, projected<_Iter, _Proj>>;
 
-#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ITERATOR_SORTABLE_H

libcxx/test/std/iterators/iterator.requirements/alg.req.mergeable/mergeable.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: libcpp-has-no-incomplete-ranges
 
 // template<class I1, class I2, class Out,
 //     class R = ranges::less, class P1 = identity, class P2 = identity>
 //   concept mergeable = see below;                           // since C++20
 
 #include <iterator>
 
 #include <functional>

libcxx/test/std/iterators/iterator.requirements/alg.req.mergeable/mergeable.subsumption.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: libcpp-has-no-incomplete-ranges
 
 // template<class I1, class I2, class Out,
 //     class R = ranges::less, class P1 = identity, class P2 = identity>
 //   concept mergeable = see below;                           // since C++20
 
 #include <iterator>
 
 #include "test_macros.h"

libcxx/test/std/iterators/iterator.requirements/alg.req.sortable/sortable.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: libcpp-has-no-incomplete-ranges
 
 // template<class I, class R = ranges::less, class P = identity>
 //   concept sortable = see below;                            // since C++20
 
 #include <iterator>
 
 #include <functional>
 

libcxx/test/std/iterators/iterator.requirements/alg.req.sortable/sortable.subsumption.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: libcpp-has-no-incomplete-ranges
 
 // template<class I, class R = ranges::less, class P = identity>
 //   concept sortable = see below;                            // since C++20
 
 #include <iterator>
 
 #include <functional>
 
 template <class I, class R, class P> void test_subsumption() requires std::permutable<I>;
 
 template <class I, class R, class P> void test_subsumption()
     requires std::indirect_strict_weak_order<R, std::projected<I, P>>;
 
 template <class I, class R, class P> constexpr bool test_subsumption() requires std::sortable<I, R, P> { return true; }
 
 static_assert(test_subsumption<int*, std::ranges::less, std::identity>());

libcxx/test/std/utilities/function.objects/range.cmp/equal_to.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::equal_to
 
 #include <functional>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/function.objects/range.cmp/greater.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::greater
 
 #include <functional>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/function.objects/range.cmp/greater_equal.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::greater_equal
 
 #include <functional>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/function.objects/range.cmp/less.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::less
 
 #include <functional>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/function.objects/range.cmp/less_equal.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::less_equal
 
 #include <functional>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/function.objects/range.cmp/not_equal_to.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: libcpp-has-no-incomplete-ranges
 
 // <functional>
 
 // ranges::not_equal_to
 
 #include <functional>
 #include <type_traits>
 #include <cassert>