Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__iterator/prev.h

@@ -0,0 +1,77 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ITERATOR_PREV_H
+#define _LIBCPP___ITERATOR_PREV_H
+
+#include <__assert>
+#include <__config>
+#include <__iterator/advance.h>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <__type_traits/enable_if.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _InputIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
+    typename enable_if<__has_input_iterator_category<_InputIter>::value, _InputIter>::type
+    prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
+  _LIBCPP_ASSERT(__n <= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
+                 "Attempt to prev(it, n) with a positive n on a non-bidirectional iterator");
+  _VSTD::advance(__x, -__n);
+  return __x;
+}
+
+#if _LIBCPP_STD_VER >= 20
+
+// [range.iter.op.prev]
+
+namespace ranges {
+namespace __prev {
+
+struct __fn {
+  template <bidirectional_iterator _Ip>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x) const {
+    --__x;
+    return __x;
+  }
+
+  template <bidirectional_iterator _Ip>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
+    ranges::advance(__x, -__n);
+    return __x;
+  }
+
+  template <bidirectional_iterator _Ip>
+  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Ip __bound_iter) const {
+    ranges::advance(__x, -__n, __bound_iter);
+    return __x;
+  }
+};
+
+} // namespace __prev
+
+inline namespace __cpo {
+  inline constexpr auto prev = __prev::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___ITERATOR_PREV_H