https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96645
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And libc++'s std::variant is still affected by the same issue, but instead of
the default constructor being deleted it just has the wrong exception
specification:
#include <variant>
void testVarStruct()
{
struct DataWithStruct {
struct A {
int number = 5; // compiles, if remove initialization
};
using Member = std::variant<A>;
Member data;
static_assert(std::is_nothrow_default_constructible_v<Member>);
};
}
The difference is that GCC defines the std::variant default constructor as
defaulted, but libc++ defines it as:
constexpr variant()
noexcept(is_nothrow_default_constructible_v<variant_alternative<0, Types...>)
That means the constructor isn't deleted for libc++, it just has the wrong
noexcept-specifier.
It looks like the nested class DataWithStruct::A isn't considered complete
until after DataWithStruct is complete, but I'm not sure why that is.
