C++: What is std::expected (C++23)?

1#include <expected>
2
3std::expected<int, std::string> parse(const std::string& s) {
4    try {
5        return std::stoi(s);
6    } catch (...) {
7        return std::unexpected("parse error");
8    }
9}
10
11auto result = parse("42");
12if (result) {
13    std::cout << *result; // 42
14} else {
15    std::cout << result.error(); // "parse error"
16}