https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94554
--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> --- (In reply to Daniel Krügler from comment #3) > The example is ill-formed because the condition of 'if constexpr' is more > restricted than that of normal 'if': It expects "a contextually converted > constant expression of type bool" and [expr.const] p10 lists the allowed > conversions in this case. This list omits the boolean conversions > ([conv.bool]). This was changed by wg21.link/p1401 so the conversion is allowed in this context as well.
