https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110197
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Looks like this issue isn't specific to constexpr array construction:
struct Currency {
constexpr Currency(int) { }
};
constexpr int f() { return __builtin_is_constant_evaluated(); };
struct A {
Currency _M_elems;
};
constexpr A _M_elems = {Currency{f()}};
Since r13-963 we reject this with
<stdin>:8:38: error: ‘A{(void)0}’ is not a constant expression
