STL support: make_unique can now handle array

Utilities/std/cm/memory

@@ -8,6 +8,8 @@
 
 #include <memory> // IWYU pragma: export
 #if !defined(CMake_HAVE_CXX_MAKE_UNIQUE)
+#  include <cstddef>
+#  include <type_traits>
 #  include <utility>
 #endif
 
@@ -19,12 +21,45 @@ using std::make_unique;
 
 #else
 
+namespace internals {
+
+template <typename T>
+struct make_unique_if
+{
+  using single = std::unique_ptr<T>;
+};
+
+template <typename T>
+struct make_unique_if<T[]>
+{
+  using unbound_array = std::unique_ptr<T[]>;
+};
+
+template <typename T, std::size_t N>
+struct make_unique_if<T[N]>
+{
+  using bound_array = void;
+};
+}
+
 template <typename T, typename... Args>
-std::unique_ptr<T> make_unique(Args&&... args)
+typename internals::make_unique_if<T>::single make_unique(Args&&... args)
 {
   return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
 }
 
+template <typename T>
+typename internals::make_unique_if<T>::unbound_array make_unique(std::size_t n)
+{
+  using E = typename std::remove_extent<T>::type;
+
+  return std::unique_ptr<T>(new E[n]());
+}
+
+template <typename T, typename... Args>
+typename internals::make_unique_if<T>::bound_array make_unique(Args&&...) =
+  delete;
+
 #endif
 
 } // namespace cm