Implement LWG#2353: std::next is over-constrained

llvm-svn: 252407

3 files changed, 10 insertions, 6 deletions

diff --git a/libcxx/include/iterator b/libcxx/include/iterator
index c06ef8f6777..8dd6bd59c1a 100644
--- a/libcxx/include/iterator
+++ b/libcxx/include/iterator
@@ -513,12 +513,12 @@ distance(_InputIter __first, _InputIter __last)
     return __distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
 }
 
-template <class _ForwardIter>
+template <class _InputIter>
 inline _LIBCPP_INLINE_VISIBILITY
-_ForwardIter
-next(_ForwardIter __x,
-     typename iterator_traits<_ForwardIter>::difference_type __n = 1,
-     typename enable_if<__is_forward_iterator<_ForwardIter>::value>::type* = 0)
+_InputIter
+next(_InputIter __x,
+     typename iterator_traits<_InputIter>::difference_type __n = 1,
+     typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0)
 {
     _VSTD::advance(__x, __n);
     return __x;
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
index f584110499b..0952588b0cb 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
@@ -12,6 +12,8 @@
 // template <InputIterator Iter>
 //   Iter next(Iter x, Iter::difference_type n = 1);
 
+// LWG #2353 relaxed the requirement on next from ForwardIterator to InputIterator
+
 #include <iterator>
 #include <cassert>
 
@@ -34,11 +36,13 @@ test(It i, It x)
 int main()
 {
     const char* s = "1234567890";
+    test(input_iterator<const char*>(s), 10, input_iterator<const char*>(s+10));
     test(forward_iterator<const char*>(s), 10, forward_iterator<const char*>(s+10));
     test(bidirectional_iterator<const char*>(s), 10, bidirectional_iterator<const char*>(s+10));
     test(random_access_iterator<const char*>(s), 10, random_access_iterator<const char*>(s+10));
     test(s, 10, s+10);
 
+    test(input_iterator<const char*>(s), input_iterator<const char*>(s+1));
     test(forward_iterator<const char*>(s), forward_iterator<const char*>(s+1));
     test(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+1));
     test(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+1));
diff --git a/libcxx/www/cxx1z_status.html b/libcxx/www/cxx1z_status.html
index 5617d877b14..afd90505ddc 100644
--- a/libcxx/www/cxx1z_status.html
+++ b/libcxx/www/cxx1z_status.html
@@ -164,7 +164,7 @@
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2259">2259</a></td><td>Issues in 17.6.5.5 rules for member functions</td><td>Kona</td><td>Complete</td></tr>
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2273">2273</a></td><td><tt>regex_match</tt> ambiguity</td><td>Kona</td><td></td></tr>
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2336">2336</a></td><td><tt>is_trivially_constructible/is_trivially_assignable</tt> traits are always false</td><td>Kona</td><td></td></tr>
-	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2353">2353</a></td><td><tt>std::next</tt> is over-constrained</td><td>Kona</td><td></td></tr>
+	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2353">2353</a></td><td><tt>std::next</tt> is over-constrained</td><td>Kona</td><td>Complete</td></tr>
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2367">2367</a></td><td><tt>pair</tt> and <tt>tuple</tt> are not correctly implemented for <tt>is_constructible</tt> with no args</td><td>Kona</td><td>Patch Ready</td></tr>
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2380">2380</a></td><td>May <tt>&lt;cstdlib&gt;</tt> provide <tt>long ::abs(long)</tt> and <tt>long long ::abs(long long)</tt>?</td><td>Kona</td><td>Complete</td></tr>
 	<tr><td><a href="http://cplusplus.github.io/LWG/lwg-defects.html#2384">2384</a></td><td>Allocator's <tt>deallocate</tt> function needs better specification</td><td>Kona</td><td>Complete</td></tr>