10 struct Ensure  struct
12     Ensure() = default;
15     Ensure(U&& functor) : functor(std::forward<U>(functor))  in Ensure()  argument
18     Ensure(F functor) : functor(std::move(functor)) {}  in Ensure()  argument
20     Ensure(Ensure&& other) = delete;
21     Ensure(const Ensure&) = delete;
23     ~Ensure()  in ~Ensure()  argument
29     Ensure& operator=(U&& other)  in operator =()  argument
36     Ensure& operator=(Ensure&& other) = delete;
38     Ensure& operator=(std::nullptr_t)  in operator =()  argument
45     Ensure& operator=(const Ensure&) = delete;