https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86751

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Jul 31 22:31:20 2018
New Revision: 263185

URL: https://gcc.gnu.org/viewcvs?rev=263185&root=gcc&view=rev
Log:
PR libstdc++/86751 default assignment operators for std::pair

The solution for PR 77537 causes ambiguities due to the extra copy
assignment operator taking a __nonesuch_no_braces parameter. By making
the base class non-assignable we don't need the extra deleted overload
in std::pair. The copy assignment operator will be implicitly deleted
(and the move assignment operator not declared) as needed. Without the
additional user-provided operator in std::pair the ambiguity is avoided.

        PR libstdc++/86751
        * include/bits/stl_pair.h (__pair_base): New class with deleted copy
        assignment operator.
        (pair): Derive from __pair_base.
        (pair::operator=): Remove deleted overload.
        * python/libstdcxx/v6/printers.py (StdPairPrinter): New pretty printer
        so that new base class isn't shown in GDB.
        * testsuite/20_util/pair/86751.cc: New test.
        * testsuite/20_util/pair/ref_assign.cc: New test.

Added:
    trunk/libstdc++-v3/testsuite/20_util/pair/86751.cc
    trunk/libstdc++-v3/testsuite/20_util/pair/ref_assign.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/stl_pair.h
    trunk/libstdc++-v3/python/libstdcxx/v6/printers.py

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