#include <iostream>
#include <string_view>
#include <string>
#include <expected>

std::expected<int, std::string> parse_int(std::string_view sv) {
    try {
        size_t pos = 0;
        int value = std::stoi(std::string(sv), &pos);
        if (pos != sv.size())
            return std::unexpected<std::string>("trailing characters");
        std::cout << "parsed\n"; // marker for EXPECT
        return value;
    } catch (const std::invalid_argument&) {
        return std::unexpected<std::string>("invalid integer");
    } catch (const std::out_of_range&) {
        return std::unexpected<std::string>("out of range");
    }
}

int main(){
    auto r1 = parse_int("123");
    if (r1) {
        std::cout << "value=" << *r1 << "\n";
    } else {
        std::cout << "error=" << r1.error() << "\n";
    }
    auto r2 = parse_int("abc");
    if (r2) {
        std::cout << "value=" << *r2 << "\n";
    } else {
        std::cout << "error=" << r2.error() << "\n";
    }
    return 0;
}