https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71579
--- Comment #2 from Antony Polukhin <antoshkka at gmail dot com> ---
You are right.
But those wrong usages are simple to catch and a static_assert with a readable
message would be a huge help for users:
template <class T>
struct assert_complete {
typedef char yes_type;
struct no_type { char data[10]; };
template <class U> static yes_type test(std::integral_constant<std::size_t,
sizeof(U)>* = 0);
template <class U> static no_type test(...);
static_assert(sizeof(test<T>(0)) == sizeof(yes_type), "T must be a complete
type");
};
// ...
template<typename _Tp, typename... _Args>
struct is_constructible
: public __is_constructible_impl<_Tp, _Args...>::type
{
static constexpr assert_complete<_Tp> _complete{};
};
Now user will get a nice error message:
main.cpp: In instantiation of 'struct assert_complete<foo>':
main.cpp:16:10: required from 'struct is_constructible<foo, foo>'
main.cpp:25:31: required from here
main.cpp:12:5: error: static assertion failed: T must be a complete type
