true if this is the only reference to this array instance; false otherwise.
Complexity: O(1).
auto a = Array!int(24, 42); assert(a.isUnique); { auto a2 = a; assert(!a.isUnique); a2.front = 0; assert(a.front == 0); } // a2 goes out of scope assert(a.isUnique);
Check whether there are no more references to this array instance.