PR libstdc++/77802

PR libstdc++/77802
    * testsuite/20_util/tuple/77802.cc: New.

    Revert:
    2016-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>
    Implement LWG 2729 for tuple.
    * include/std/tuple (_Tuple_impl(_Tuple_impl&&)):
    Suppress conditionally.
    (_Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&&)): Likewise.
    (__is_tuple_impl_trait_impl, __is_tuple_impl_trait): New.
    (_Tuple_impl(const _Head&)): Constrain.
    (_Tuple_impl(_UHead&&)): Likewise.
    (_Tuple_impl(_Tuple_impl&&)): Suppress conditionally.
    (_Tuple_impl(const _Tuple_impl<_Idx, _UHead>&)): Constrain.
    (_Tuple_impl(_Tuple_impl<_Idx, _UHead>&&)): Likewise.
    (operator=(const tuple&)): Enable conditionally.
    (operator=(tuple&&)): Suppress conditionally.
    (operator=(const tuple<_UElements...>&)): Constrain.
    (operator=(tuple<_UElements...>&&)): Likewise.
    (operator=(const tuple&)): Enable conditionally (2-param tuple).
    (operator=(tuple&&)): Suppress conditionally (2-param tuple).
    (operator=(const tuple<_U1, _U2>&)): Constrain.
    (operator=(tuple<_U1, _U2>&&)): Likewise.
    (operator=(const pair<_U1, _U2>&)): Likewise.
    (operator=(pair<_U1, _U2>&&)): Likewise.
    * testsuite/20_util/tuple/element_access/get_neg.cc: Adjust.
    * testsuite/20_util/tuple/tuple_traits.cc: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@240709 138bc75d-0d04-0410-961f-82ee72b054a4