`randomUUID` should never have been marked as `@trusted`, which clearly got missed in the review process (which inevitably happens sometimes - we'll never catch everything), so this really does need to be fixed. But as it's already `@trusted`, we can fix it later.

And in general, I think that we need to strongly favor _not_ marking functions as `@trusted` even if that reduces what we can do in `@safe` code, otherwise we run a serious risk of completely negating the benefits of `@safe` by having code which is considered to be safe when it isn't. We've already had problems where stuff has been marked with `@trusted` when it wasn't actually safe (particularly with some of the stuff in druntime). So, we need to be very skeptical of any functions being marked with `@trusted`.