Previously, this did not compile in VS 2017, because `new T(initializer_())` would try to call the copy constructor of `T`. Now, `initializer_` will construct the `T` inplace.
Previously, this did not compile in VS 2017, because `new T(initializer_())` would try to call the copy constructor of `T`. Now, `initializer_` will construct the `T` inplace.