尝试使用 std::make_unique() 从初始化列表构造一个向量

Question

I struggle to understand the code below. Why can v2 be constructed from an initializer list, but v3 fails?

#include <vector>
#include <memory>

int main()
{
  auto v1 = std::make_unique<std::vector<int>>(std::vector<int>({1,2,3,4,5})); // works

  auto x = {1,2,3,4,5};
  auto v2 = std::make_unique<std::vector<int>>(x); // works

  //auto v3 = std::make_unique<std::vector<int>>({1,2,3,4,5}); // fails
}

Can someone explain, or point me to a resource that clarifies this behaviour?

Answer 1

Thanks for pointing me to the answer, @joergbrech.

Paraphrasing the answer: the reason is a subtle difference between auto type deduction and template type deduction:

From "Effective Modern C++" by Scott Meyers:

auto type deduction is usually the same as template type deduction, but auto type deduction assumes that a braced initializer represents a std::initializer_list , and template type deduction doesn't.