[Bug c++/95789] [10/11 Regression] Const method is allowed to return non-const reference on template class

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95789

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Marek Polacek
<mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:315b87f63bcde4c881e9963c39d57258da08ccb5

commit r10-8497-g315b87f63bcde4c881e9963c39d57258da08ccb5
Author: Marek Polacek <polacek@redhat.com>
Date:   Mon Jun 22 21:26:49 2020 -0400

    c++: Make convert_like complain about bad ck_ref_bind again [PR95789]

    convert_like issues errors about bad_p conversions at the beginning
    of the function, but in the ck_ref_bind case, it only issues them
    after we've called convert_like on the next conversion.

    This doesn't work as expected since r10-7096 because when we see
    a conversion from/to class type in a template, we return early, thereby
    missing the error, and a bad_p conversion goes by undetected.  That
    made the attached test to compile even though it should not.

    I had thought that I could just move the ck_ref_bind/bad_p errors
    above to the rest of them, but that regressed diagnostics because
    expr then wasn't converted yet by the nested convert_like_real call.

    So, for bad_p conversions, do the normal processing, but still return
    the IMPLICIT_CONV_EXPR to avoid introducing trees that the template
    processing can't handle well.  This I achieved by adding a wrapper
    function.

    gcc/cp/ChangeLog:

            PR c++/95789
            PR c++/96104
            PR c++/96179
            * call.c (convert_like_real_1): Renamed from convert_like_real.
            (convert_like_real): New wrapper for convert_like_real_1.

    gcc/testsuite/ChangeLog:

            PR c++/95789
            PR c++/96104
            PR c++/96179
            * g++.dg/conversion/ref4.C: New test.
            * g++.dg/conversion/ref5.C: New test.
            * g++.dg/conversion/ref6.C: New test.

    (cherry picked from commit 8e64d182850560dbedfabb88aac90d4fc6155067)