[Bug c++/70323] [6 regression] missing error on integer overflow in constexpr function result converted to bool

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70323

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 38054
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38054&action=edit
gcc6-pr70323.patch

This seems like it would work, but haven't bootstrapped/regtested it yet.