Can't really construct a box with non-list initialization

[tusooa]

Currently we have 3 ways to initialize a box with value T{...} but no way to initialize one with value T(...). These causes problems for types with a constructor that takes a std::initializer_list. For example, the following prints out 2 50 2:

struct test
{
    test(int a) : a(a) {}
    test(const test& that) : a(that.a) {}
    test(test &&that) : a(that.a) {}
    template<class T>
    test(const std::initializer_list<T> &l) {
        a = 50;
    }
    int a;
};
int main()
{
    test t1(2);
    immer::box<test> t2(t1);
    test t3(t1);
    std::cout << t1.a << std::endl << t2.get().a << std::endl << t3.a << std::endl;
}

A real-life example would be https://github.com/nlohmann/json, for which the list initialization wraps whatever passed to it into a JSON array.

I think we need to have some strategy to differentiate between these two.

[arximboldi]

Ohhh, damn initializer lists. What compilation error are you getting? That case is intended to work. I think I can figure a way to fix that particular case by specifically distinguishing copy/move constructing the underlying T.

[tusooa]

Ohhh, damn initializer lists. What compilation error are you getting? That case is intended to work. I think I can figure a way to fix that particular case by specifically distinguishing copy/move constructing the underlying T.

Not a compilation error, but I have no way to invoke the other constructors than the one taking an initializer_list.