[Bug c++/88815] [9 Regression] is_constexpr (based on narrowing conversion and expression SFINAE) broken

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88815

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
And of course r265789 changed int{(p(), 0U)} from being dependent to being
non-dependent, so scenario 2) to scenario 1).