GCC 8.2.1. Compilation error: invalid conversion from...

[Ptomaine]

• What is the issue you have?
  The compilation error:

/include/nlohmann/detail/iterators/iter_impl.hpp:262:48: error: invalid conversion from 'const nlohmann::basic_json<ordered_map>*' to 'nlohma
nn::detail::iter_impl<nlohmann::basic_json<ordered_map> >::pointer' {aka 'nlohmann::basic_json<ordered_map>*'} [-fpermissive]
                 return &(m_it.object_iterator->second);
                         ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~

ordered_map is defined as following:

template<class Key, class T, class Ignore, class Allocator, class Hash = std::hash<Key>, class KeyEqual = std::equal_to<Key>>
using ordered_map = tsl::ordered_map<Key, T, Hash, KeyEqual, typename std::allocator_traits<Allocator>::template rebind_alloc<std::pair<Key, T>>>;

namespace json
{
using namespace nlohmann;
using json_ord = basic_json<ordered_map>;
}

inline json::json_ord operator "" _json_ord(const char* s, std::size_t n)
{
    return json::json_ord::parse(s, s + n);
}

inline json::json_ord::json_pointer operator "" _json_ord_pointer(const char* s, std::size_t n)
{
    return json::json_ord::json_pointer(std::string(s, n));
}

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?
  Just use the previous definitions to create a json object that uses ordered_map.

• What is the expected behavior?
  No compilation errors or warnings.

• And what is the actual behavior instead?
  A compilation error or warning if -fpermissive option provided.

• Which compiler and operating system are you using? Is it a supported compiler?
  GCC/MinGW 8.2.1

• Did you use a released version of the library or the version from the develop branch?
  The MinGW distribution package was downloaded from https://gcc-mcf.lhmouse.com/

• If you experience a compilation error: can you compile and run the unit tests?

[nlohmann]

Related: #546

[nlohmann]

In #546, the following hint for integration was made: #546 (comment). I cannot compile your code snippet either - it seems that the interfaces of std::map and tsl::ordered_map and the library fails to compile because of this.

[nlohmann]

I'm not sure what do do here...