[libcxx] Define istream_iterator equality comparison operators out-of-line

[miyuki]

Summary

[libcxx] Define istream_iterator equality comparison operators out-of-line

Currently libc++ defines operator== and operator!= as friend functions in the definition of the istream_iterator class template. Such definition has a subtle difference from an out-of-line definition required by the C++ Standard: these functions can only be found by argument-dependent lookup, but not by qualified lookup.

This patch changes the definition, so that it conforms to the C++ Standard and adds a check involving qualified lookup to the test suite.

[EricWF]

LGTM. Thanks.

[miyuki]

In D40415#934939, @EricWF wrote:

LGTM. Thanks.

I don't have write access. Please commit the patch on my behalf.

[miyuki]

Ping

[rogfer01]

Hi @miyuki I can commit it.

[miyuki]

In D40415#950793, @rogfer01 wrote:

Hi @miyuki I can commit it.

Please do so.

include/iterator

_LIBCPP_INLINE_VISIBILITY istream_iterator& operator++()
         {
             if (!(*__in_stream_ >> __value_))
                 __in_stream_ = 0;
             return *this;
         }
     _LIBCPP_INLINE_VISIBILITY istream_iterator  operator++(int)
         {istream_iterator __t(*this); ++(*this); return __t;}
 
+    template <class _Up, class _CharU, class _TraitsU, class _DistanceU>
     friend _LIBCPP_INLINE_VISIBILITY
-    bool operator==(const istream_iterator& __x, const istream_iterator& __y)
-        {return __x.__in_stream_ == __y.__in_stream_;}
+    bool
+    operator==(const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __x,
+               const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __y);
 
+    template <class _Up, class _CharU, class _TraitsU, class _DistanceU>
     friend _LIBCPP_INLINE_VISIBILITY
-    bool operator!=(const istream_iterator& __x, const istream_iterator& __y)
-        {return !(__x == __y);}
+    bool
+    operator==(const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __x,
+               const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __y);
 };
 
+template <class _Tp, class _CharT, class _Traits, class _Distance>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __x,
+           const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __y)
+{
+    return __x.__in_stream_ == __y.__in_stream_;
+}
+
+template <class _Tp, class _CharT, class _Traits, class _Distance>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __x,
+           const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __y)
+{
+    return !(__x == __y);
+}
+
 template <class _Tp, class _CharT = char, class _Traits = char_traits<_CharT> >
 class _LIBCPP_TEMPLATE_VIS ostream_iterator
     : public iterator<output_iterator_tag, void, void, void, void>
 {
 public:
     typedef _CharT char_type;
     typedef _Traits traits_type;
     typedef basic_ostream<_CharT,_Traits> ostream_type;

test/std/iterators/stream.iterators/istream.iterator/istream.iterator.ops/equal.pass.cpp

int main()
     assert(i2 != i5);
 
     assert(i3 == i3);
     assert(i3 != i4);
     assert(i3 != i5);
 
     assert(i4 == i4);
     assert(i4 == i5);
+
+    assert(std::operator==(i1, i2));
+    assert(std::operator!=(i1, i3));
 }