CLionFail.cpp

#include <type_traits>

template <typename...TArgs>
struct TypeList {};

// Assume TElement is not in the list unless proven otherwise
template < typename TElement, typename TList >
struct ContainsType {
    static constexpr bool value = false;
};

// If it matches the first type, it is definitely in the list
template < typename TElement, typename... TTail >
struct ContainsType < TElement, TypeList < TElement, TTail... > >
{
    static constexpr bool value = true;
};

// If it is not the first element, check the remaining list
template < typename TElement, typename THead, typename... TTail >
struct ContainsType < TElement, TypeList < THead, TTail... > >
{
    static constexpr bool value = (ContainsType < TElement, TypeList < TTail... > >::value);
};

template <typename ...Types>
struct TypeAdder;

template<class ...Types>
struct BuilderType {};

template<typename ...Types>
struct BuilderType<TypeList<Types...> > {
    typedef TypeAdder<Types...> TypeAdder;
};

template<typename T, typename TList>
struct AddType;

template<typename T, typename ... TArgs>
struct AddType< T, TypeList<TArgs...> >
{
    typedef typename std::conditional<
            ContainsType<T, TypeList<TArgs...> >::value,
            TypeList<TArgs... >,
            TypeList<T, TArgs... >
    >::type type;
};

template <typename ...Types>
struct TypeAdder
{
    template <typename T>
    using with = typename BuilderType<typename AddType<T, TypeList<Types...> >::type>::TypeAdder;
    int value;
};

struct A {
    int a;
};

struct B {
    int b;
};

int main()
{
    TypeAdder<>
    ::with<A>
    ::with<B> b;
    b.value = 0;
    return b.value;
}