Simple Scope-guard(defer) implementation under C++17.

defer.hpp

#pragma once
#ifndef DEFER_HPP_DEFINED
#define DEFER_HPP_DEFINED

/*
    defer.hpp v20190325
    Simple Scope-guard(defer) implementation under C++17.
    Released under MIT License.

    Support: C++17
    Usage: 
        1. Include defer.hpp
        2. Pass any callable object into Defer's constructor.

    Example 1:
        Defer defer = [] () {
            std::cout << "Defer" << std::endl;
        };

    Example 2:
        void func() {
            std::cout << "Defer" << std::endl;
        }

        int main() {
            std::function<void()> f = func;
            Defer defer = f;
        }
*/

template <class T>
class Defer {
public:
    Defer(T& fn) : fn(fn) {}
    Defer(T&& fn) : fn(std::move(fn)) {}

    // The object is unmovable once it's constructed.
    Defer() noexcept = delete;
    Defer(const Defer &) noexcept = delete;
    Defer(const Defer &&) noexcept = delete;
    Defer& operator=(const Defer &) noexcept = delete;
    Defer& operator=(const Defer &&) noexcept = delete;
    void* operator new (std::size_t) noexcept = delete;
    void* operator new[](std::size_t) noexcept = delete;

    ~Defer() {
        this->fn();
    }

private:
    T fn;
};

#endif