36     constexpr O o1;    // disengaged  in main()  local
42     static_assert(o1 == o1, "");  in main()
43     static_assert(o1 == o2, "");  in main()
44     static_assert(!(o1 == o3), "");  in main()
45     static_assert(!(o1 == o4), "");  in main()
46     static_assert(!(o1 == o5), "");  in main()
48     static_assert(o2 == o1, "");  in main()
54     static_assert(!(o3 == o1), "");  in main()
60     static_assert(!(o4 == o1), "");  in main()
66     static_assert(!(o5 == o1), "");  in main()
73     using O1 = optional<int>;  in main()  typedef
75     constexpr O1 o1(42);  in main()  local
76     static_assert(o1 == O2(42), "");  in main()
77     static_assert(!(O2(101) == o1), "");  in main()
80     using O1 = optional<int>;  in main()  typedef
82     constexpr O1 o1(42);  in main()  local
83     static_assert(o1 == O2(42), "");  in main()
84     static_assert(!(O2(101) == o1), "");  in main()