[Bug libstdc++/60270] New: [C++1y] std::quoted is too eager to clear the string

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60270

            Bug ID: 60270
           Summary: [C++1y] std::quoted is too eager to clear the string
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

Lars Gullik Bjønnes pointed out that we clear the string too early in
std::quoted, which causes this to fail:

#include <string>
#include <sstream>
#include <iomanip>
#include <cassert>

int main()
{
  std::istringstream in;
  std::string s = "xxx";
  in >> s;
  assert( !s.empty() );
  in >> std::quoted(s);
  assert( !s.empty() );  // fails
}