errors.txt

In file included from test.pass.cpp:3:
In file included from /opt/gcc-tot/include/c++/7.0.0/tuple:38:
In file included from /opt/gcc-tot/include/c++/7.0.0/utility:70:
In file included from /opt/gcc-tot/include/c++/7.0.0/bits/stl_pair.h:59:
In file included from /opt/gcc-tot/include/c++/7.0.0/bits/move.h:57:
/opt/gcc-tot/include/c++/7.0.0/type_traits:139:14: error: base class has incomplete type
    : public _B1
      ~~~~~~~^~~
/opt/gcc-tot/include/c++/7.0.0/tuple:485:14: note: in instantiation of template class 'std::__and_<std::is_constructible<dynamic, Optional<std::tuple<dynamic> > &&> >' requested here
      return __and_<is_constructible<_Elements, _UElements&&>...>::value;
             ^
/opt/gcc-tot/include/c++/7.0.0/tuple:641:21: note: in instantiation of function template specialization 'std::_TC<true, dynamic>::_MoveConstructibleTuple<Optional<std::tuple<dynamic> >
      >' requested here
                    _MoveConstructibleTuple<_UElements...>()
                    ^
/opt/gcc-tot/include/c++/7.0.0/tuple:646:19: note: while substituting prior template arguments into non-type template parameter [with _UElements = <Optional<std::tuple<dynamic> >>]
        constexpr tuple(_UElements&&... __elements)
                  ^~~~~
/opt/gcc-tot/include/c++/7.0.0/type_traits:976:28: note: while substituting deduced template arguments into function template 'tuple' [with _UElements = <Optional<std::tuple<dynamic>
      >>, $1 = (no value)]
             = decltype(::new _Tp(declval<_Arg>()))>
                                  ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:977:24: note: in instantiation of default argument for '__test<dynamic, Optional<std::tuple<dynamic> > &&>' required here
      static true_type __test(int);
                       ^~~~~~~~~~~
/opt/gcc-tot/include/c++/7.0.0/type_traits:987:24: note: (skipping 3 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
      typedef decltype(__test<_Tp, _Arg>(0)) type;
                       ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:1070:14: note: in instantiation of template class 'std::__is_direct_constructible_new_safe<dynamic, Optional<std::tuple<dynamic> > &&>'
      requested here
    : public conditional<is_reference<_Tp>::value,
             ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:1078:14: note: in instantiation of template class 'std::__is_direct_constructible_new<dynamic, Optional<std::tuple<dynamic> > &&>' requested
      here
    : public __is_direct_constructible_new<_Tp, _Arg>::type
             ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:1118:14: note: in instantiation of template class 'std::__is_direct_constructible<dynamic, Optional<std::tuple<dynamic> > &&>' requested here
    : public __is_direct_constructible<_Tp, _Arg>
             ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:1129:14: note: in instantiation of template class 'std::__is_constructible_impl<dynamic, Optional<std::tuple<dynamic> > &&>' requested here
    : public __is_constructible_impl<_Tp, _Args...>::type
             ^
test.pass.cpp:19:24: note: in instantiation of template class 'std::is_constructible<dynamic, Optional<std::tuple<dynamic> > &&>' requested here
    static_assert(std::is_constructible<dynamic, Optional<std::tuple<dynamic>>&&>::value, "");
                       ^
/opt/gcc-tot/include/c++/7.0.0/type_traits:1128:12: note: definition of 'std::is_constructible<dynamic, Optional<std::tuple<dynamic> > &&>' is not complete until the closing '}'
    struct is_constructible
           ^
1 error generated.

repro.cpp

// repro.cpp
// this is minimized code from folly library
#include<tuple>
template<class Value>
struct Optional {
Optional() = default;
  // implicit
  Optional(const Value&) {}
};

struct dynamic {
  // implicit
  template<class T> dynamic(T) {}
};

Optional<std::tuple<dynamic>> get() { return {}; }

int main() {
    static_assert(std::is_constructible<dynamic, Optional<std::tuple<dynamic>>&&>::value, "");
    auto x = get();
}