2333 struct RandomCover(Range, UniformRNG = void)  struct
2336     private Range _input;
2337     private bool[] _chosen;
2338     private size_t _current;
2339     private size_t _alreadyChosen = 0;
2340     private bool _isEmpty = false;
2344         this(Range input)  in this()
2360         private UniformRNG _rng;
2362         this(Range input, ref UniformRNG rng)  in this()
2377         this(Range input, UniformRNG rng)  in this()
2385         @property size_t length()  in length()
2391     @property auto ref front()  in front()
2397     void popFront()  in popFront()
2453     return RandomCover!(Range, UniformRNG)(r, rng);  in randomCover()  argument