std::unordered_map in struct, serialization

[014972304505347]

• What is the issue you have?

Cannot build deserialization code for a std::unordered_map. Following the example in the README at https://github.com/nlohmann/json#arbitrary-types-conversions

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

  #include <unordered_map>
  #include <vector>
  #include <string>
  #include <nlohmann/json.hpp>
  
  struct myStruct{
    std::string structName;
  }
    		
  struct myStructCollection {
    std::unordered_map<int, myStruct> myStructs;
    myStructCollection(std::unordered_map<int, myStruct> myStructs) : myStructs (myStructs){}
  };
  
  void from_json(const json& j, myStructCollection& p) {
    p.myStructs = j.at("myStructs").get<std::unordered_map<int, myStruct>>();
  }
  

• What is the expected behavior?

Builds. According to https://github.com/nlohmann/json#conversion-from-stl-containers, std::unordered_map is supported.

• And what is the actual behavior instead?

Error at line 269 of "utility":

  pair& operator=(pair&& _Right)
    _NOEXCEPT_COND(is_nothrow_move_assignable_v<_Ty1>
    && is_nothrow_move_assignable_v<_Ty2>)
  {	// assign from moved pair
    first = _STD forward<_Ty1>(_Right.first); // ERROR ON THIS LINE!!!!
    second = _STD forward<_Ty2>(_Right.second);
    return (*this);
  }

Error C2166 "l-value specifies const object "

• Which compiler and operating system are you using? Is it a supported compiler?

MSVC compiler 19.14.26430, Windows 10, Visual Studio 2017 (version 15.7.2), v141 toolset.

• Did you use a released version of the library or the version from the develop branch?

Used vcpkg to install.

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

[theodelrieu]

It should be fixed on the develop branch, could you try it out?

[014972304505347]

I just got the latest on the develop branch, and am still having the same issue.
Just to confirm - it is headers only?

[theodelrieu]

Yes the library is header only. I did fix the issue for std::map, but not for std::unordered_map. Will open a PR next week.