Bug 17047 – std.algorithm.iteration.splitter should propagate bidirectionality

For splitter with a range as separator, the propagation for bidirectionality (back, popBack) is missing, see e.g.: https://github.com/dlang/phobos/blob/3d98191ce9fee0d2bf2b2c4982242afe413e37bd/std/algorithm/iteration.d#L3839 Moreover, there are no tests either for the bidirectionaility of splitter with a sole element as splitter. It might even be possible to unify both splitter implementations - they look pretty similar.

https://github.com/dlang/phobos/pull/6150 > Making splitter a bidirectional range fundamentally broken - at least if the delimiter has more than one element. Think about something like --- auto result = "*******".splitter("**"); // odd number in the string being split, even number in the delimeter --- > The range is not going to have the same elements if it's iterated from the back. It will end up being split differently.