[Bug c++/115163] Requesting better diagnostic for explicit constructor failure

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115163

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathaniel Shead <nsh...@gcc.gnu.org>:

https://gcc.gnu.org/g:3e8ce187dc4595da3d2f41a0fb09ee9cd2e437ff

commit r16-6707-g3e8ce187dc4595da3d2f41a0fb09ee9cd2e437ff
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date:   Sun Jan 11 10:02:45 2026 +1100

    c++: Improve diagnostic for implicit conversion errors [PR115163]

    This patch adds a note to indicate if any viable explicit conversion
    functions were skipped if an implicit conversion failed to occur.

    Perhaps the base diagnostic in ocp_convert can be further improved for
    class types as well, as the current message is not very clear, but I've
    not looked into that for this patch.

            PR c++/115163

    gcc/cp/ChangeLog:

            * call.cc (implicit_conversion_error): Add flags argument, call
            maybe_show_nonconverting_candidate.
            (build_converted_constant_expr_internal): Pass flags to
            implicit_conversion_error.
            (perform_implicit_conversion_flags): Likewise.
            * cvt.cc (ocp_convert): Call maybe_show_nonconverting_candidate
            on conversion error.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/is_convertible7.C: Add new testcases.
            * g++.dg/diagnostic/explicit2.C: New test.

    Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
    Reviewed-by: Jason Merrill <ja...@redhat.com>