overloaded.hpp

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#pragma once
 
/// @file userver/utils/overloaded.hpp
/// @brief @copybrief utils::Overloaded
 
#include <variant>
 
USERVER_NAMESPACE_BEGIN
 
namespace utils {
 
/// @ingroup userver_universal
///
/// @brief Utility to define std::variant visitors in a simple way
template <class... Ts>
struct Overloaded : Ts... {  // NOLINT(fuchsia-multiple-inheritance)
  using Ts::operator()...;
};
 
template <class... Ts>
Overloaded(Ts...) -> Overloaded<Ts...>;
 
template <class... Args, class... Ts>
constexpr decltype(auto) Visit(const std::variant<Args...>& var, Ts&&... ts) {
  return std::visit(Overloaded{std::forward<Ts>(ts)...}, var);
}
 
template <class... Args, class... Ts>
constexpr decltype(auto) Visit(std::variant<Args...>& var, Ts&&... ts) {
  return std::visit(Overloaded{std::forward<Ts>(ts)...}, var);
}
 
template <class... Args, class... Ts>
constexpr decltype(auto) Visit(std::variant<Args...>&& var, Ts&&... ts) {
  return std::visit(Overloaded{std::forward<Ts>(ts)...}, std::move(var));
}
 
}  // namespace utils
 
USERVER_NAMESPACE_END