System.List = type<T> {
	flatten = => {
		-> (list<System.List>) {
			switch (list.count) {
				case (0) { list }
				case (1) { [ self(list.head) ] }
				else     { [ ...self(list.head), ...self(list.tail) ] }
			}
		}
		-> (object<System.Object>) { object }
	}

	@.flatten = -> {
		@.type.flatten(@)
	}
}