callables.h

/*
 * AUI Framework - Declarative UI toolkit for modern C++20
 * Copyright (C) 2020-2025 Alex2772 and Contributors
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
//
// Created by Alex2772 on 11/19/2021.
//
 
#pragma once
 
#include "members.h"
 
namespace aui {
 
   template<typename F>
   concept not_overloaded_lambda = requires(F&& f) {
       // we can't 100% guarantee that T is actual lambda, but C++ lambdas have following traits:
       std::is_class_v<F>;
       { &std::decay_t<F>::operator() };
   };
 
   static_assert(not_overloaded_lambda<decltype([]{})>, "aui::not_overloaded_lambda failed");
   static_assert(not_overloaded_lambda<decltype([](int v){})>, "aui::not_overloaded_lambda failed");

   template<typename... Lambdas>
   struct lambda_overloaded : Lambdas... {
       using Lambdas::operator()...;
   };
 
   // deduction guide
   template<typename... Lambdas>
   lambda_overloaded(Lambdas...) -> lambda_overloaded<Lambdas...>;
 
   template<typename Return, typename... Args>
   struct function_info;
 
   template<typename Return, typename... Args>
   struct function_info<Return(Args...)> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename Return, typename... Args>
   struct function_info<Return(*)(Args...)> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename Return, typename... Args>
   struct function_info<Return(&)(Args...)> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename Return, typename... Args>
   struct function_info<Return(Args...) noexcept> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename Return, typename... Args>
   struct function_info<Return(*)(Args...) noexcept> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename Return, typename... Args>
   struct function_info<Return(&)(Args...) noexcept> {
       using return_t = Return;
       using args = std::tuple<Args...>;
   };
 
   template<typename T>
   concept function_pointer = requires(T&& t) {
       typename function_info<T>::args;
   };
 
   template<not_overloaded_lambda Lambda>
   using lambda_info = ::aui::reflect::member<decltype(&Lambda::operator())>;

   struct identity
   {
       template<typename T>
       [[nodiscard]]
       constexpr T&& operator()(T&& t) const noexcept { return std::forward<T>(t); }
   };
}

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