[Bug libstdc++/94051] New: #include <iosfwd> & <string_view> is not enough for operator<<

[joerg.richter@pdv-fs.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94051

            Bug ID: 94051
           Summary: #include <iosfwd> & <string_view> is not enough for
                    operator<<
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joerg.richter@pdv-fs.de
  Target Milestone: ---

#include <iosfwd>
#include <string_view>

std::ostream& func( std::ostream& os, std::string_view v )
{
  return os << v;
}

This code results in a compile error:
'__ostream_insert' was not declared in this scope

It would be nice if this two includes would be enough to stream a string_view.
This works already for <string>.
Adding the small <bits/ostream_insert.h> header to <string_view> fixes the
problem.