[Bug c++/88337] Implement P1002R1, P1327R1, P1330R0, C++20 relaxations of constexpr restrictions.

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88337

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Looks like we need to teach constexpr how to evaluate a call to __dynamic_cast.