[Bug c++/81311] [7/8 Regression] An std::ref argument calls copy constructor instead of template constructor in C++17 mode

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81311

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Mar 22 03:53:19 2018
New Revision: 258755

URL: https://gcc.gnu.org/viewcvs?rev=258755&root=gcc&view=rev
Log:
        PR c++/81311 - wrong C++17 overload resolution.

        * call.c (build_user_type_conversion_1): Remove C++17 code.
        (conv_binds_ref_to_prvalue): New.
        (build_over_call): Handle C++17 copy elision.
        (build_special_member_call): Only do C++17 copy elision here if the
        argument is already the right type.

Added:
    trunk/gcc/testsuite/g++.dg/overload/conv-op2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c