std :: function的模板替换失败

Question

我无法弄清楚为什么编译器抱怨这段代码的模板替换失败

struct Report {
    double val;
    vector<string> props;
};

template <typename T>
void solve(
    const  Report& report,
    std::function<T(const double, const string&)> map) {
    vector<T> results;
    results.reserve(report.props.size());
    for (const auto& prop : report.props) {
      results.emplace_back(map(report.val, prop));
    }
}

int main(int argc, char const *argv[]) {
    solve(Report(), [](const double x, const string&y) -> int {
        return 1;
    });

    return 0;
}

我收到以下编译错误

note: candidate template ignored: could not match 'function<type-parameter-0-0
(double, const std::__1::basic_string<char> &)>' against '(lambda at 
test.cpp:29:18)'