Building xeus failed with Visual Studio 2019 due to implicit conversion failed

[LilyWangL]

When I build xeus with Visual Studio 2019, it built failed and I got this error:

xeus\src\ee70dfa02b-e9875865ca\src\xkernel_configuration.cpp(28): error C2593: 'operator =' is ambiguous
xeus\src\ee70dfa02b-e9875865ca\src\xkernel_configuration.cpp(29): error C2593: 'operator =' is ambiguous
xeus\src\ee70dfa02b-e9875865ca\src\xkernel_configuration.cpp(38): error C2593: 'operator =' is ambiguous

This is source code in xkernel_configuration.cpp:

        std::ifstream ifs(file_name);

        nl::json doc;
        ifs >> doc;

        xconfiguration res;
        res.m_transport = doc["transport"];
        res.m_ip = doc["ip"];
        res.m_control_port = std::to_string(doc["control_port"].get<int>());
        res.m_shell_port = std::to_string(doc["shell_port"].get<int>());
        res.m_stdin_port = std::to_string(doc["stdin_port"].get<int>());
        res.m_iopub_port = std::to_string(doc["iopub_port"].get<int>());
        res.m_hb_port = std::to_string(doc["hb_port"].get<int>());
        res.m_signature_scheme = doc.value("signature_scheme", "");
        if (res.m_signature_scheme != "")
        {
            res.m_key = doc["key"];
        }
        else
        {
            res.m_key = "";
        }

The type of res.m_transport is string. When converting nl::json doc to string, it failed. I try to modify doc["transport"] to doc["transport"].get<std::string>(), it build successfully. But I don't know this change is correct or not. Who can help me to confirm it?

Thanks.

[SylvainCorlay]

Thanks for reporting and opening a PR. This looks like a (yet another) MSVC compiler bug.

I will comment on the PR.

[SylvainCorlay]

Hey @LilyWangL a PR to xeus core applying the same patch would be very welcome.

Would you be fine with opening one (and enabling VS 2019 in the build matrix?)

[SylvainCorlay]

This is now fixed in 0.23.3. Closing.