46         impl<$($Fut: Future),*> Future for $Join<$($Fut),*> {  impl
113     Fut1: Future,  in join()
114     Fut2: Future,  in join()
142     Fut1: Future,  in join3()
143     Fut2: Future,  in join3()
144     Fut3: Future,  in join3()
174     Fut1: Future,  in join4()
175     Fut2: Future,  in join4()
176     Fut3: Future,  in join4()
177     Fut4: Future,  in join4()
209     Fut1: Future,  in join5()
210     Fut2: Future,  in join5()
211     Fut3: Future,  in join5()
212     Fut4: Future,  in join5()
213     Fut5: Future,  in join5()