Incomplete types reported by (experimental) GCC10

[LarsGullik]

Hi,

I am doing test compiles with the experimental unreleased GCC10. And am getting some errors
that I do not see with GCC9. I am in contact with GCC maintainers, and they can not see that
this is a gcc/libstdc++ bug. However there has been some changes in libstdc++ mostly to improve/correct requirements (on types in std::variant).

I have attached sources that compiles with GCC9 but that fails with GCC10. All related to nlohmann/json and std::variant and some incomlete type being reported.

It would be nice figure out if this is a problem in nlohmann/json or in GCC10/libstdc++ before the actual release of GCC10.

This is v3.7.3 of nlohmann/json.
GCC10 as of gcc (GCC) 10.0.1 20200120 (experimental)
GCC9 as of gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1)

presentation.txt

[LarsGullik]

The attachment is the errors I get, GCC10 called as:

/opt/gcc/gcc-10/bin/g++ -O2 -std=gnu++17 -c presentation.cpp

error.txt

[LarsGullik]

Simpler reproducer:

#include "nlohmann/json.hpp"
#include <variant>

typedef std::variant<nlohmann::json> cb_data;

struct R {
    R()
        : cb_(nlohmann::json{{"one", "two"}})
    {}

    cb_data cb_;
};

[LarsGullik]

This (non-)bug reported to GCC seems to be related:
GCC Bug

[nickaein]

Possibly relevant to: #1920

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[t-b]

Building the tests fails with

$/rest/inst/gcc-trunk/usr/local/bin/gcc --version
gcc (GCC) 10.0.1 20200406 (experimental)

and here is what I got:

[ 91%] Building CXX object test/CMakeFiles/test-concepts.dir/src/unit-concepts.cpp.o
cd /home/firma/devel/json/build/test && /rest/inst/gcc-trunk/usr/local/bin/g++  -DDOCTEST_CONFIG_SUPER_FAST_ASSERTS -I/home/firma/devel/json/test/thirdparty/doctest -I/home/firma/devel/json/test/thirdparty/fifo_map -I/home/firma/devel/json/single_include  -g   -Wno-deprecated -Wno-float-equal -Wno-deprecated-declarations -o CMakeFiles/test-concepts.dir/src/unit-concepts.cpp.o -c /home/firma/devel/json/test/src/unit-concepts.cpp
In file included from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/move.h:57,
                 from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_pair.h:59,
                 from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/utility:70,
                 from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/algorithm:60,
                 from /home/firma/devel/json/single_include/nlohmann/json.hpp:37,
                 from /home/firma/devel/json/test/src/unit-concepts.cpp:32:
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits: In instantiation of ‘struct std::is_constructible<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>’:
/home/firma/devel/json/single_include/nlohmann/json.hpp:11436:79:   required by substitution of ‘template<class ... Args, typename std::enable_if<std::is_constructible<nlohmann::basic_json<>, Args ...>::value, int>::type <anonymous> > nlohmann::detail::json_ref<nlohmann::basic_json<> >::json_ref(Args&& ...) [with Args = {const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&}; typename std::enable_if<std::is_constructible<nlohmann::basic_json<>, Args ...>::value, int>::type <anonymous> = <missing>]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits:901:30:   required from ‘struct std::__is_constructible_impl<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits:930:12:   required from ‘struct std::__is_copy_constructible_impl<nlohmann::basic_json<>, true>’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits:936:12:   required from ‘struct std::is_copy_constructible<nlohmann::basic_json<> >’
/home/firma/devel/json/test/src/unit-concepts.cpp:104:13:   required from here
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits:906:12: error: invalid use of incomplete type ‘struct std::__is_constructible_impl<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>’
  906 |     struct is_constructible
      |            ^~~~~~~~~~~~~~~~
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/type_traits:900:12: note: declaration of ‘struct std::__is_constructible_impl<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>’
  900 |     struct __is_constructible_impl
      |            ^~~~~~~~~~~~~~~~~~~~~~~
In file included from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/utility:70,
                 from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/algorithm:60,
                 from /home/firma/devel/json/single_include/nlohmann/json.hpp:37,
                 from /home/firma/devel/json/test/src/unit-concepts.cpp:32:
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_pair.h: In instantiation of ‘static constexpr bool std::_PCC<<anonymous>, _T1, _T2>::_ConstructiblePair() [with _U1 = const std::__cxx11::basic_string<char>; _U2 = nlohmann::basic_json<>; bool <anonymous> = true; _T1 = const std::__cxx11::basic_string<char>; _T2 = nlohmann::basic_json<>]’:
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_pair.h:261:35:   required by substitution of ‘template<class _U1, class _U2, typename std::enable_if<(_ConstructiblePair<_U1, _U2>() && _ImplicitlyConvertiblePair<_U1, _U2>()), bool>::type <anonymous> > constexpr std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >::pair(const std::__cxx11::basic_string<char>&, const nlohmann::basic_json<>&) [with _U1 = const std::__cxx11::basic_string<char>; _U2 = nlohmann::basic_json<>; typename std::enable_if<(_ConstructiblePair<_U1, _U2>() && _ImplicitlyConvertiblePair<_U1, _U2>()), bool>::type <anonymous> = <missing>]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/alloc_traits.h:504:20:   required from ‘static void std::allocator_traits<std::allocator<_CharT> >::construct(std::allocator_traits<std::allocator<_CharT> >::allocator_type&, _Up*, _Args&& ...) [with _Up = std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >; _Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>}; _Tp = std::_Rb_tree_node<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; std::allocator_traits<std::allocator<_CharT> >::allocator_type = std::allocator<std::_Rb_tree_node<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > > >]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_tree.h:614:32:   required from ‘void std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_construct_node(std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Link_type, _Args&& ...) [with _Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>}; _Key = std::__cxx11::basic_string<char>; _Val = std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >; _KeyOfValue = std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; _Compare = std::less<void>; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Link_type = std::_Rb_tree_node<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >*]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_tree.h:631:21:   required from ‘std::_Rb_tree_node<_Val>* std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_create_node(_Args&& ...) [with _Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>}; _Key = std::__cxx11::basic_string<char>; _Val = std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >; _KeyOfValue = std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; _Compare = std::less<void>; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Link_type = std::_Rb_tree_node<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >*]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_tree.h:2399:33:   required from ‘std::pair<std::_Rb_tree_iterator<_Val>, bool> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_emplace_unique(_Args&& ...) [with _Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>}; _Key = std::__cxx11::basic_string<char>; _Val = std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >; _KeyOfValue = std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; _Compare = std::less<void>; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_map.h:577:33:   required from ‘std::pair<typename std::_Rb_tree<_Key, std::pair<const _Key, _Tp>, std::_Select1st<std::pair<const _Key, _Tp> >, _Compare, typename __gnu_cxx::__alloc_traits<_Allocator>::rebind<std::pair<const _Key, _Tp> >::other>::iterator, bool> std::map<_Key, _Tp, _Compare, _Alloc>::emplace(_Args&& ...) [with _Args = {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>}; _Key = std::__cxx11::basic_string<char>; _Tp = nlohmann::basic_json<>; _Compare = std::less<void>; _Alloc = std::allocator<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >; typename std::_Rb_tree<_Key, std::pair<const _Key, _Tp>, std::_Select1st<std::pair<const _Key, _Tp> >, _Compare, typename __gnu_cxx::__alloc_traits<_Allocator>::rebind<std::pair<const _Key, _Tp> >::other>::iterator = std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> >, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > >, std::less<void>, std::allocator<std::pair<const std::__cxx11::basic_string<char>, nlohmann::basic_json<> > > >::iterator]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:16352:40:   required from ‘nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::basic_json(nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::initializer_list_t, bool, nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::value_t) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::initializer_list_t = std::initializer_list<nlohmann::detail::json_ref<nlohmann::basic_json<> > >; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::value_t = nlohmann::detail::value_t]’
/home/firma/devel/json/test/src/unit-concepts.cpp:154:32:   required from here
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_pair.h:106:45: error: ‘value’ is not a member of ‘std::__and_<std::is_constructible<const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&>, std::is_constructible<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&> >’
  106 |         is_constructible<_T2, const _U2&>>::value;
      |                                             ^~~~~
In file included from /rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/memory:66,
                 from /home/firma/devel/json/single_include/nlohmann/json.hpp:45,
                 from /home/firma/devel/json/test/src/unit-concepts.cpp:32:
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_uninitialized.h: In instantiation of ‘_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<const nlohmann::basic_json<>*, std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > > >; _ForwardIterator = nlohmann::basic_json<>*]’:
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_uninitialized.h:325:37:   required from ‘_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = __gnu_cxx::__normal_iterator<const nlohmann::basic_json<>*, std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > > >; _ForwardIterator = nlohmann::basic_json<>*; _Tp = nlohmann::basic_json<>]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_vector.h:555:31:   required from ‘std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = nlohmann::basic_json<>; _Alloc = std::allocator<nlohmann::basic_json<> >]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/ext/new_allocator.h:151:4:   required from ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Up*, _Args&& ...) [with _Up = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >; _Args = {const std::vector<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer> > >&}; _Tp = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >]’
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/alloc_traits.h:507:17:   required from ‘static void std::allocator_traits<std::allocator<_CharT> >::construct(std::allocator_traits<std::allocator<_CharT> >::allocator_type&, _Up*, _Args&& ...) [with _Up = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >; _Args = {const std::vector<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer> > >&}; _Tp = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >; std::allocator_traits<std::allocator<_CharT> >::allocator_type = std::allocator<std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > > >]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:15697:35:   required from ‘static T* nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::create(Args&& ...) [with T = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >; Args = {const std::vector<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer> > >&}; ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:15849:36:   required from ‘nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::json_value::json_value(const array_t&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::array_t = std::vector<nlohmann::basic_json<>, std::allocator<nlohmann::basic_json<> > >]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:16681:25:   required from ‘nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::basic_json(const nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:11454:17:   required from ‘nlohmann::detail::json_ref<BasicJsonType>::value_type nlohmann::detail::json_ref<BasicJsonType>::moved_or_copied() const [with BasicJsonType = nlohmann::basic_json<>; nlohmann::detail::json_ref<BasicJsonType>::value_type = nlohmann::basic_json<>]’
/home/firma/devel/json/single_include/nlohmann/json.hpp:16351:59:   required from ‘nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::basic_json(nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::initializer_list_t, bool, nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::value_t) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::initializer_list_t = std::initializer_list<nlohmann::detail::json_ref<nlohmann::basic_json<> > >; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::value_t = nlohmann::detail::value_t]’
/home/firma/devel/json/test/src/unit-concepts.cpp:154:32:   required from here
/rest/inst/gcc-trunk/usr/local/include/c++/10.0.1/bits/stl_uninitialized.h:137:72: error: ‘value’ is not a member of ‘std::is_constructible<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>’
  137 |       static_assert(is_constructible<_ValueType2, decltype(*__first)>::value,
      |                                                                        ^~~~~
make[2]: *** [test/CMakeFiles/test-concepts.dir/build.make:66: test/CMakeFiles/test-concepts.dir/src/unit-concepts.cpp.o] Fehler 1
make[2]: Verzeichnis „/home/firma/devel/json/build“ wird verlassen
make[1]: *** [CMakeFiles/Makefile2:2221: test/CMakeFiles/test-concepts.dir/all] Fehler 2
make[1]: Verzeichnis „/home/firma/devel/json/build“ wird verlassen
make: *** [Makefile:144: all] Fehler 2