15     enum State { CONSTRUCTED, MOVED_FROM, DESTROYED };  enum
16     State state;
18     TrackedValue() : state(State::CONSTRUCTED) {}  in TrackedValue()
20     TrackedValue(TrackedValue const& t) : state(State::CONSTRUCTED) {  in TrackedValue()
21         assert(t.state != State::MOVED_FROM && "copying a moved-from object");  in TrackedValue()
22         assert(t.state != State::DESTROYED  && "copying a destroyed object");  in TrackedValue()
26     TrackedValue(TrackedValue&& t) : state(State::CONSTRUCTED) {  in TrackedValue()
27         assert(t.state != State::MOVED_FROM && "double moving from an object");  in TrackedValue()
28         assert(t.state != State::DESTROYED  && "moving from a destroyed object");  in TrackedValue()
29         t.state = State::MOVED_FROM;  in TrackedValue()
34         assert(state != State::DESTROYED && "copy assigning into destroyed object");
35         assert(t.state != State::MOVED_FROM && "copying a moved-from object");
36         assert(t.state != State::DESTROYED  && "copying a destroyed object");
43         assert(state != State::DESTROYED && "move assigning into destroyed object");
44         assert(t.state != State::MOVED_FROM && "double moving from an object");
45         assert(t.state != State::DESTROYED  && "moving from a destroyed object");
47         t.state = State::MOVED_FROM;
53         assert(state != State::DESTROYED && "double-destroying an object");  in ~TrackedValue()
54         state = State::DESTROYED;  in ~TrackedValue()