[libc++][ranges] implement 'ranges::shift_left'

Author: xiaoyang-sde

libcxx/include/__algorithm/shift_left.h

@@ -17,7 +17,7 @@
 #include <__utility/pair.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS
@@ -28,11 +28,9 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 #if _LIBCPP_STD_VER >= 20
 
 template <class _AlgPolicy, class _Iter, class _Sent>
-_LIBCPP_HIDE_FROM_ABI constexpr pair<_Iter, _Iter> __shift_left(
-    _Iter __first, _Sent __last,
-    typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __n) {
-  _LIBCPP_ASSERT_UNCATEGORIZED(__n >= 0,
-                               "__n must be greater than or equal to 0");
+_LIBCPP_HIDE_FROM_ABI constexpr pair<_Iter, _Iter>
+__shift_left(_Iter __first, _Sent __last, typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __n) {
+  _LIBCPP_ASSERT_UNCATEGORIZED(__n >= 0, "__n must be greater than or equal to 0");
 
   if (__n == 0) {
     _Iter __end = _IterOps<_AlgPolicy>::next(__first, __last);
@@ -61,11 +59,10 @@ _LIBCPP_HIDE_FROM_ABI constexpr pair<_Iter, _Iter> __shift_left(
 
 template <class _ForwardIterator>
 inline _LIBCPP_HIDE_FROM_ABI constexpr _ForwardIterator
-shift_left(_ForwardIterator __first, _ForwardIterator __last,
+shift_left(_ForwardIterator __first,
+           _ForwardIterator __last,
            typename iterator_traits<_ForwardIterator>::difference_type __n) {
-  return std::__shift_left<_ClassicAlgPolicy>(std::move(__first),
-                                              std::move(__last), __n)
-      .second;
+  return std::__shift_left<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __n).second;
 }
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/test/std/algorithms/alg.modifying.operations/alg.shift/ranges.shift_left.pass.cpp

@@ -27,22 +27,31 @@
 #include "test_iterators.h"
 #include "MoveOnly.h"
 
-template <class Iter, class Sent = Iter>
-concept HasShiftLeftIt = requires(Iter iter, Sent sent, std::size_t n) { std::ranges::shift_left(iter, sent, n); };
+struct InvalidDifferenceT {};
+
+template <class Iter, class Sent = Iter, class N = std::iter_difference_t<Iter>>
+concept HasShiftLeftIt = requires(Iter iter, Sent sent, N n) { std::ranges::shift_left(iter, sent, n); };
 
 static_assert(HasShiftLeftIt<int*>);
+static_assert(HasShiftLeftIt<int*, sentinel_wrapper<int*>>);
+static_assert(HasShiftLeftIt<int*, sized_sentinel<int*>>);
+
 static_assert(!HasShiftLeftIt<ForwardIteratorNotDerivedFrom>);
 static_assert(!HasShiftLeftIt<PermutableNotForwardIterator>);
 static_assert(!HasShiftLeftIt<PermutableNotSwappable>);
 
-template <class Range>
-concept HasShiftLeftR = requires(Range range, std::size_t n) { std::ranges::shift_left(range, n); };
+static_assert(!HasShiftLeftIt<int*, int*, InvalidDifferenceT>);
+
+template <class Range, class N = std::ranges::range_difference_t<Range>>
+concept HasShiftLeftR = requires(Range range, N n) { std::ranges::shift_left(range, n); };
 
 static_assert(HasShiftLeftR<UncheckedRange<int*>>);
 static_assert(!HasShiftLeftR<ForwardRangeNotDerivedFrom>);
 static_assert(!HasShiftLeftR<PermutableRangeNotForwardIterator>);
 static_assert(!HasShiftLeftR<PermutableRangeNotSwappable>);
 
+static_assert(!HasShiftLeftR<UncheckedRange<int*>, InvalidDifferenceT>);
+
 template <class Iter, class Sent>
 constexpr void test_iter_sent() {
   {