Modified from N3588, make_unique; a syntax enthusiast's work.

make_unique.cc

#include <type_traits>
#include <iostream>
#include <memory>

struct default_init_t {};
default_init_t default_init;

template <typename T, typename = void>
struct make_unique;

template <typename T>
struct make_unique<T, typename std::enable_if<
not std::is_array<T>::value>::type> : std::unique_ptr<T> {
	template <typename... Args>
	make_unique(Args&&... args) :
		std::unique_ptr<T>(new T(std::forward<Args>(args)...)) {}
	make_unique(default_init_t) :
		std::unique_ptr<T>(new T) {}

	operator std::unique_ptr<T>() && {
		return this;
	}
};

template <typename T>
struct make_unique<T, typename std::enable_if<
std::is_array<T>::value>::type> {
	make_unique() : braced_(true) {}
	make_unique(size_t n) : braced_(false), sz_(n) {}

	make_unique(make_unique&&) = delete;
	make_unique& operator=(make_unique&&) = delete;

	template <typename... Args>
	auto operator()(Args&&... args) && -> std::unique_ptr<T> {
		typedef typename std::remove_extent<T>::type U;

		return std::unique_ptr<T>(braced_ ?
		    new U[sizeof...(Args)]{ std::forward<Args>(args)... } :
		    new U[sz_]{ std::forward<Args>(args)... });
	}

	auto operator()(default_init_t) && -> std::unique_ptr<T> {
		typedef typename std::remove_extent<T>::type U;

		return std::unique_ptr<T>(new U[sz_]);
	}

private:
	bool braced_;
	size_t sz_;
};


// STL's tests

using namespace std;

void print(const unique_ptr<int[]>& up) {
    for (int i = 0; i < 5; ++i) {
        cout << up[i] << " ";
    }

    cout << endl;
}

void f(unique_ptr<int>) {}

int main() {
    cout << *make_unique<int>() << endl;
    cout << *make_unique<int>(1729) << endl;
    cout << "\"" << *make_unique<string>() << "\"" << endl;
    cout << "\"" << *make_unique<string>("meow") << "\"" << endl;
    cout << "\"" << *make_unique<string>(6, 'z') << "\"" << endl;

    cout << *make_unique<int>(default_init) << endl;
    cout << "\"" << *make_unique<string>(default_init) << "\"" << endl;

    print(make_unique<int[]>{5}());
    print(make_unique<int[]>{5}(default_init));
    print(make_unique<int[]>{5}(100, 200, 300));
    print(make_unique<int[]>{}(111, 222, 333, 444, 555));
    f(make_unique<int>(3));
}