scope_guard.cpp

#include <utility>

template< std::size_t I, typename F >
struct wrapper { F f; };

template< std::size_t I, typename F >
constexpr
F &
get(wrapper< I, F > * sg) noexcept
{
    return sg->f;
}

template< typename index_sequence, typename ...F >
struct scope_guard_base;
    
template < std::size_t ...I, typename ...F >
struct scope_guard_base< std::index_sequence< I... >, F... >
    : wrapper< I, F >...
{
    using base = scope_guard_base;
    scope_guard_base(F &... f) : wrapper< I, F >{std::forward< F >(f)}... { ; }
    ~scope_guard_base() { (get< (sizeof...(I) - 1 - I) >(this)(), ...); }
};

template< typename ...F >
struct scope_guard
    : scope_guard_base< std::index_sequence_for< F... >, F... >
{
    scope_guard(F &&... f) : scope_guard::base(f...) { ; }
};

#include <iostream>

template< std::size_t I >
struct F
{
    
    F() { std::cout << I << std::endl; }

    void operator () () const { std::cout << I << std::endl; }

};

int main()
{
    F< 0 > const f{};
    scope_guard _{f, F< 1 >{}, F< 2 >{}};
}