I'm unsure that any of the functions in `Cycle!StaticArray` can be safe, since they reference a static array, that may have gone out of scope. EG:

```D
auto fun()
{
    int[3] buf;
    return cycle(buf);
}
```
If you do this, then ask for the front of the returned value, you're going to have a bad time.

I'll admit though that in these cases I'm unsure *which* functions are the ones that should be marked unsafe. Arguably, it's the constructor itself that's unsafe (keeps a reference to an outside arg), but the rest of the functions should be safe? Or just mark the whole lot of them as unsafe and be done with it...