RAII file reader that closes on scope exit

#include <fstream>
#include <iostream>
#include <stdexcept>
#include <string>
#include <utility>
#include <vector>

// Owns an ifstream and closes it when the object leaves scope.
class FileReader {
public:
    explicit FileReader(const std::string& path) : in_(path) {
        if (!in_) {
            throw std::runtime_error("cannot open " + path);
        }
    }
    FileReader(const FileReader&) = delete;
    FileReader& operator=(const FileReader&) = delete;
    std::vector<std::string> lines() {
        std::vector<std::string> out;
        for (std::string line; std::getline(in_, line);) {
            out.push_back(std::move(line));
        }
        return out;
    }

private:
    std::ifstream in_;
};

int main() {
    try {
        FileReader reader("notes.txt");
        for (const auto& line : reader.lines()) {
            std::cout << line << '\n';
        }
    } catch (const std::exception& error) {
        std::cerr << "error: " << error.what() << '\n';
        return 1;
    }
}