[Bug c++/91212] [8/9/10/11 Regression] const ignored for ctor arguments within return since r8-2493-g4ce8c5dea53d8073

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91212

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:81bc0ec3e926d7a2c90502847ddaacf3d56d5b75

commit r11-2411-g81bc0ec3e926d7a2c90502847ddaacf3d56d5b75
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jul 29 00:57:40 2020 -0400

    c++: Avoid calling const copy ctor on implicit move. [PR91212]

    Our implementation of C++11 implicit move was wrong for return; we didn't
    actually hit the check for the type of the first parameter of the selected
    constructor, because we didn't see LOOKUP_PREFER_RVALUE set properly.

    Fixing that to look at the right flags fixed the issue for this testcase,
    but broke implicit move for a by-value converting constructor (PR58051).  I
    think this was not allowed in C++17, but it is allowed under the implicit
    move changes from C++20, and those changes were voted to apply as a DR to
    earlier standards as well, so I don't want to break it now.

    So after fixing the flags check I changed the test to allow value
    parameters.

    gcc/cp/ChangeLog:

            PR c++/91212
            * call.c (build_over_call): Don't call a const ref
            overload for implicit move.

    gcc/testsuite/ChangeLog:

            PR c++/91212
            * g++.dg/cpp0x/move-return3.C: New test.