[libc++] Fix copy-paste damage in `ranges::rotate_copy` and its test (#74544)

Found while running libc++'s tests with MSVC's STL.

`ranges::rotate_copy` takes `forward_iterator`s as this test's comment
banner correctly depicts. However, this test had bogus assertions
expecting that `ranges::rotate_copy` would be constrained away for
not-quite-**bidi** iterators. @philnik777 confirmed that these were
copy-paste relics from the `ranges::reverse_copy` test.

I fixed this by replacing the assertions with the test types that aren't
quite **forward** iterators/ranges. Additionally, I noticed that the
top-level `test()` function was missing coverage with the weakest
possible `forward_iterator<int*>`.

This revealed that the product code in `ranges_rotate_copy.h` was
similarly damaged. In addition to fixing it by taking `forward_iterator`
and `forward_range` as depicted in the Standard, this drops the
inclusion of `<__iterator/reverse_iterator.h>` as this algorithm doesn't
need `std::__reverse_range`.

1 files changed, 5 insertions, 4 deletions

diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/ranges.rotate_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/ranges.rotate_copy.pass.cpp
index 1f18d78..58b0f75 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/ranges.rotate_copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/ranges.rotate_copy.pass.cpp
@@ -34,16 +34,16 @@ template <class Range, class Out = int*>
 concept HasRotateCopyR = requires(Range range, Out out) { std::ranges::rotate_copy(range, nullptr, out); };
 
 static_assert(HasRotateCopyIt<int*>);
-static_assert(!HasRotateCopyIt<BidirectionalIteratorNotDerivedFrom>);
-static_assert(!HasRotateCopyIt<BidirectionalIteratorNotDecrementable>);
+static_assert(!HasRotateCopyIt<ForwardIteratorNotDerivedFrom>);
+static_assert(!HasRotateCopyIt<ForwardIteratorNotIncrementable>);
 static_assert(!HasRotateCopyIt<int*, SentinelForNotSemiregular>);
 static_assert(!HasRotateCopyIt<int*, SentinelForNotWeaklyEqualityComparableWith>);
 static_assert(!HasRotateCopyIt<int*, OutputIteratorNotIndirectlyWritable>);
 static_assert(!HasRotateCopyIt<int*, OutputIteratorNotInputOrOutputIterator>);
 
 static_assert(HasRotateCopyR<UncheckedRange<int*>>);
-static_assert(!HasRotateCopyR<BidirectionalRangeNotDerivedFrom>);
-static_assert(!HasRotateCopyR<BidirectionalRangeNotDecrementable>);
+static_assert(!HasRotateCopyR<ForwardRangeNotDerivedFrom>);
+static_assert(!HasRotateCopyR<ForwardRangeNotIncrementable>);
 static_assert(!HasRotateCopyR<UncheckedRange<int*, SentinelForNotSemiregular>>);
 static_assert(!HasRotateCopyR<UncheckedRange<int*>, OutputIteratorNotIndirectlyWritable>);
 static_assert(!HasRotateCopyR<UncheckedRange<int*>, OutputIteratorNotInputOrOutputIterator>);
@@ -112,6 +112,7 @@ constexpr void test_out_iterators() {
 }
 
 constexpr bool test() {
+  test_out_iterators<forward_iterator<int*>>();
   test_out_iterators<bidirectional_iterator<int*>>();
   test_out_iterators<random_access_iterator<int*>>();
   test_out_iterators<contiguous_iterator<int*>>();