https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63458
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> --- You forgot to mark your operator bool as explicit.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63458
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> --- You forgot to mark your operator bool as explicit.