https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88815
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> --- That is most likely a bug in the package. GCC 8 wasn't very good at detecting narrow conversions, but in GCC 9 things have improved, so probably we just detect invalid code now. The problem in this PR is that we still don't detect narrow conversions in certain contexts (here, decltype).
