为什么我会"No viable conversion from 'vector<Country>' to 'int'"？

我真的不确定为什么会收到这个错误。我试过用谷歌搜索，但没有得到最好的结果。。。如果有人能告诉我为什么我会出现这个错误：

No viable conversion from 'vector<Country>' to 'int'

int main()
{
    vector<Country> readCountryInfo(const string& filename);
    // Creating empty vector
    vector<Country> myVector;
    // Opening file
    ifstream in;
    in.open("worldpop.txt");
    if (in.fail()) {
        throw invalid_argument("invalid file name");
    }
    while (in) {
        char buffer; // Character buffer
        int num; // Integer to hold population
        string countryName; // Add character buffer to create name
        while (in.get(buffer)) {
            // Check if buffer is a digit
            if (isdigit(buffer)) {
                in.unget();
                in >> num;
            }
            // Check if buffer is an alphabetical character
            else if (isalpha(buffer) || (buffer == ' ' && isalpha(in.peek()))) {
                countryName += buffer;
            }
            // Checking for punctuation to print
            else if (ispunct(buffer)) {
                countryName += buffer;
            }
            // Check for new line or end of file
            else if (buffer == 'n' || in.eof()) {
                // Break so it doesn't grab next char from inFile when running loop
                break;
            }
        }
        Country newCountry = {countryName, num};
        myVector.push_back(newCountry);
    }
    return myVector;
}