How to implement "dereference and post-increment" for input iterator in C++?

Requirements for InputIterator include *i++ with an equivalent expression being

value_type x = *i;
++i;
return x;

How can one declare such an operator without implementing the standard post-increment i++ returning a non-void value (which InputIterators are not required to do)?

You may use a proxy for the post increment:

#include <iostream>

class input_iterator
{
    private:
    class post_increment_proxy
    {
        public:
        post_increment_proxy(int value) : value(value) {}
        int operator * () const { return value; }

        private:
        int value;
    };

    public:
    post_increment_proxy operator ++ (int) {
        post_increment_proxy result{value};
        ++value;
        return result;
    }

    private:
    int value = 0;
};


int main() {
    input_iterator i;
    std::cout << *i++ << '\n';
    std::cout << *i++ << '\n';
    std::cout << *i++ << '\n';
}