Add forward declaration of operator<< in <string_view> as required.

This declaration was previously missing despite appearing in the
synopsis. Users are still required to include <ostream> to get the
definition of the streaming operator.

llvm-svn: 372909

1 files changed, 7 insertions, 0 deletions

diff --git a/libcxx/include/string_view b/libcxx/include/string_view
index 3a30db8b17b..8a684a8f966 100644
--- a/libcxx/include/string_view
+++ b/libcxx/include/string_view
@@ -173,6 +173,7 @@ namespace std {
 
 #include <__config>
 #include <__string>
+#include <iosfwd>
 #include <algorithm>
 #include <iterator>
 #include <limits>
@@ -767,6 +768,12 @@ bool operator>=(typename common_type<basic_string_view<_CharT, _Traits> >::type
     return __lhs.compare(__rhs) >= 0;
 }
 
+
+template<class _CharT, class _Traits>
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os,
+           basic_string_view<_CharT, _Traits> __str);
+
 typedef basic_string_view<char>     string_view;
 #ifndef _LIBCPP_NO_HAS_CHAR8_T
 typedef basic_string_view<char8_t>  u8string_view;