Calling constructor with braces

Simple question about C++11 syntax. There is a sample code (reduced one from the importance of std::function):

struct Wanderer
{
  explicit Wanderer(std::vector<std::function<void (float)>> & update_loop)
  {
    update_loop.emplace_back([this](float dt) { update(dt); });
  }
  void update(float dt);
};

int main()
{
  std::vector<std::function<void (float)>> update_loop;
  Wanderer wanderer{update_loop}; // why {} ???
}

I'd like to know how it is possible to call the constructor with curly braces like Wanderer wanderer{update_loop};. It is neither an initializer list, nor uniform initialization. What is this?

It is neither initializer list, nor uniform initialization. What's the thing is this?

Your premise is wrong. It is uniform initialization and, in Standardese terms, direct-brace-initialization.

Unless a constructor accepting an std::initializer_list is present, using braces for constructing objects is equivalent to using parentheses.

The advantage of using braces is that the syntax is immune to the Most Vexing Parse problem:

struct Y { };

struct X
{
    X(Y) { }
};

// ...

X x1(Y()); // MVP: Declares a function called x1 which returns
           // a value of type X and accepts a function that
           // takes no argument and returns a value of type Y.

X x2{Y()}; // OK, constructs an object of type X called x2 and
           // provides a default-constructed temporary object 
           // of type Y in input to X's constructor.