Build failure using clang 5

Bug Report

• What is the issue you have?

The project failed to build

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?

See here for a build log. The error generated is below:

In file included from /home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:31:
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/src/json.hpp:12061:40: error: no viable overloaded '='
            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
            ~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:585:35: note: in instantiation of member function 'nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>::insert' requested here
                auto it = j_array.insert(j_array.begin(), 3, 5);
                                  ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit copy assignment operator) not viable: cannot convert argument of incomplete type 'void' to 'const __gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument
    class __normal_iterator
          ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit move assignment operator) not viable: cannot convert argument of incomplete type 'void' to '__gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument
In file included from /home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:31:
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/src/json.hpp:12125:36: error: no viable overloaded '='
        result.m_it.array_iterator = m_value.array->insert(
        ~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:627:35: note: in instantiation of member function 'nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>::insert' requested here
                auto it = j_array.insert(j_array.end(), j_other_array.begin(), j_other_array.end());
                                  ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit copy assignment operator) not viable: cannot convert argument of incomplete type 'void' to 'const __gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument
    class __normal_iterator
          ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit move assignment operator) not viable: cannot convert argument of incomplete type 'void' to '__gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument
In file included from /home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:31:
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/src/json.hpp:12172:36: error: no viable overloaded '='
        result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist.begin(), ilist.end());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/conda/staged-recipes/build_artifacts/nlohmann_json_1515513797346/work/json-3.0.1/test/src/unit-modifiers.cpp:696:35: note: in instantiation of member function 'nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>::insert' requested here
                auto it = j_array.insert(j_array.begin(), {7, 8, 9});
                                  ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit copy assignment operator) not viable: cannot convert argument of incomplete type 'void' to 'const __gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument
    class __normal_iterator
          ^
/opt/rh/devtoolset-2/root/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/bits/stl_iterator.h:708:11: note: candidate function (the implicit move assignment operator) not viable: cannot convert argument of incomplete type 'void' to '__gnu_cxx::__normal_iterator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> *, std::vector<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::allocator<nlohmann::basic_json<std::map, std::vector, std::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> > > >' for 1st argument

Sorry, it's clear after posting this that libcxx is too old.