Type of member pointer not recognised as <value type>

Question

The following code example tries to extract the value types of member pointer of a struct foo previously fed into a function serialize().

This maybe needs further explanation: I want to eventually iterate through each member of the struct foo and apply certain operations based on the value types of each member pointer. Have a look:

Demo

#include <cstdio>
#include <utility>
#include <tuple>
#include <typeinfo>

/* Struct with two int members */

struct foo
{
    int a_;
    int b_;
};

/* Saves member pointers */

template<auto Ptr>
struct proxy
{
    decltype(Ptr) mem_ptr_;
};

/* Conglomerate of all member ptrs of a struct */

template <typename T>
struct type_descriptor;

template <>
struct type_descriptor<foo>
{
    using type = std::tuple<proxy<&foo::a_>, proxy<&foo::b_>>;
};

/* Extract member ptr value type */

template<typename T>
struct member_pointer_value;

template<typename Class, typename Value>
struct member_pointer_value<Value Class::*>
{
    using type = Value;
};

/* Iterate over each member ptr and compare */

template<typename T, std::size_t... I>
auto serialize_impl(const T& mystruct , std::index_sequence<I...> indices)
{
    ([](){
        using value_type = member_pointer_value<decltype(std::tuple_element_t<I, typename type_descriptor<T>::type>::mem_ptr_)>::type;
        
        printf("%s\n", typeid(value_type).name());
        if constexpr (std::is_same_v<int, std::remove_cvref<value_type>>) {
            printf("Is int!\n");
            // ...
        } else {
            printf("Is not int :(\n");
            // ... 
        }
    }(), ...);
}

template <typename T, typename Indices = std::make_index_sequence<std::tuple_size_v<typename type_descriptor<T>::type>>>
auto serialize(T mystruct)
{
    serialize_impl(mystruct, Indices{});
}

int main()
{
    foo f0;
    serialize(f0);
}

Problem:

std::is_same_v doesn't return true in the constexpr check, so the non-int branch is taken, which is not intended. Interestingly, typeinfo (included for debug purposes only) gives me a type of "i" which I always thought of as "integer"... What is happening?

Answer 1

You are mixing up std::remove_cvref and std::remove_cvref_t, I believe it's a typo somehow.

Demo