What is wrong with my lambda in fold expression

I'm trying to form std::vector of smart pointers to objects in the following way:

#include <iostream>
#include <vector>
#include <memory>

template<typename... Args>
std::vector<std::shared_ptr<int>> createSourceVector(Args... args)
{
    std::vector<std::shared_ptr<int>> result;
    (
        [&]() {
            result.push_back(std::make_shared<int>(args));
        },
        ...);
    return result;
}

int main()
{
    auto sources = createSourceVector(1,2,3);
    std::cout << sources.size() << '\n'; // 0

    return 0;
}

However, the result vector is always empty. It seems that fold expression doesn't see properly my result variable. How to fix it?

The lambda that does the push_back is not being invoked (Clang gives a warning about this https://godbolt.org/z/zzhfT993G).

You need to add an () after the lambda:

(
  [&]() {
    result.push_back(std::make_shared<int>(args));
  }(),  // <-- add () here
...);

However, you don't need a lambda at all. You can just write the fold expression like this:

(result.push_back(std::make_shared<int>(args)), ...);

You can also initialize the returned vector directly in a braced-initializer:

return {std::make_shared<int>(args)...};

If the return type is deduced with auto, you can still write:

return std::vector<std::shared_ptr<int>>{
         std::make_shared<int>(args)...
       };