[Bug libstdc++/79141] [6/7 Regression] std::pair p = {}; fails to compile due to ambiguous overload

[ville at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79141

--- Comment #5 from ville at gcc dot gnu.org ---
Author: ville
Date: Mon Apr  3 21:20:23 2017
New Revision: 246663

URL: https://gcc.gnu.org/viewcvs?rev=246663&root=gcc&view=rev
Log:
PR libstdc++/79141

Backport from mainline
2017-04-03  Ville Voutilainen  <ville.voutilai...@gmail.com>

        PR libstdc++/79141
        * include/bits/stl_pair.h (__nonesuch_no_braces): New.
        (operator=(typename conditional<
        __and_<is_copy_assignable<_T1>,
        is_copy_assignable<_T2>>::value,
        const pair&, const __nonesuch&>::type)): Change __nonesuch
        to __nonesuch_no_braces.
        (operator=(typename conditional<
        __not_<__and_<is_copy_assignable<_T1>,
        is_copy_assignable<_T2>>>::value,
        const pair&, const __nonesuch&>::type)): Likewise.
        (operator=(typename conditional<
        __and_<is_move_assignable<_T1>,
        is_move_assignable<_T2>>::value,
        pair&&, __nonesuch&&>::type)): Likewise.
        * testsuite/20_util/pair/79141.cc: New.

Added:
    branches/gcc-6-branch/libstdc++-v3/testsuite/20_util/pair/79141.cc
Modified:
    branches/gcc-6-branch/libstdc++-v3/ChangeLog
    branches/gcc-6-branch/libstdc++-v3/include/bits/stl_pair.h