[v3 PATCH] Implement LWG 2534, Constrain rvalue stream operators.

[Jonathan Wakely]

On 27/11/16 20:50 +0200, Ville Voutilainen wrote:
>    Implement LWG 2534, Constrain rvalue stream operators.
>    * include/std/istream (__is_convertible_to_basic_istream): New.
>    (__is_extractable): Likewise.
>    (operator>>(basic_istream<_CharT, _Traits>&&, _Tp&&)):
>    Turn the stream parameter into a template parameter
>    and constrain.
>    * include/std/ostream /__is_convertible_to_basic_ostream): New.
>    (__is_insertable): Likewise.
>    (operator<<(basic_ostream<_CharT, _Traits>&&, const _Tp&)):
>    Turn the stream parameter into a template parameter
>    and constrain.
>    * testsuite/27_io/basic_istream/extractors_other/char/4.cc: New.
>    * testsuite/27_io/basic_istream/extractors_other/wchar_t/4.cc:
>    Likewise.
>    * testsuite/27_io/basic_ostream/inserters_other/char/6.cc: Likewise.
>    * testsuite/27_io/basic_ostream/inserters_other/wchar_t/6.cc: Likewise.

OK, thanks.