#include <string_view>
#include <filesystem>
#include <fstream>
#include <iostream>

using namespace std;
namespace fs = experimental::filesystem;

fs::path data_path;
ifstream filestream;

fs::path FileSystemManager::GetDataPath()
{
    return data_path;
}

FileSystemManager filesystem;

void openfile(string_view file_name)
{
    //filestream = ifstream(filesystem.GetDataPath() / string(file_name)); // это работает
    filestream = ifstream(filesystem.GetDataPath() / file_name); // это нет
    if (!filestream)
    {
        //throw underflow_error;
        return;
    }
}