match.hpp

#pragma once

#include <utility>
#include <variant>

template <typename... Ts>
struct Overloaded : Ts... {
  using Ts::operator()...;
};

template <typename... Ts>
Overloaded(Ts...) -> Overloaded<Ts...>;

template <typename T>
class Matcher {
 public:
  template <typename U>
  Matcher(U&& value) : value_{std::forward<U>(value)} {
  }

  template <typename F>
  decltype(auto) operator<<=(F&& f) {
    return std::visit(std::forward<F>(f), std::forward<T>(value_));
  }

 private:
  T&& value_;
};

template <typename U>
Matcher(U &&) -> Matcher<U&&>;

#define match(var) Matcher(var) <<= Overloaded