https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103653
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- >But I think auto(x) should also be well-formed. it is well formed as a declaration. auto(x) = 1; Unless something changed in that part of C++ standard too. The following does work as expected too: int main() { int x = 0; float t; t = auto(x); }