I use a class OneOrMoreIntHelper that accepts both a single integer as well as an initializer list of integers, and that works great to construct instances of Class through a single constructor.

However, this fails when trying to use emplace_back. E.g., this code example does not compile:

#include <initializer_list>
#include <vector>

struct OneOrMoreIntHelper {
    OneOrMoreIntHelper(const int value) {}
    OneOrMoreIntHelper(const std::initializer_list<int> &) {}
};

struct Class {
    Class(OneOrMoreIntHelper) {}
};

void foo() {
    Class single_int(0);
    Class list_two_ints({0, 0});

    std::vector<Class> instances;
    // this works fine
    instances.emplace_back(0);
    
    // error: no matching function for call to ‘std::vector::emplace_back()’
    instances.emplace_back({0, 0}); 
    
    // Workaround
    instances.push_back(OneOrMoreIntHelper{0, 0});
}

I have found the workaround above, but ideally, I would like to not have to instantiate the OneOrMoreIntHelper object at all (in the end, the whole point is to be able to type 0 instead of {0}, so having to type OneOrMoreIntHelper{0, 0} elsewhere complete defeats the purpose).