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Mark Simulacrum
5f732eba7a
Document unintuitive argument order for Vec::dedup_by relation When trying to use `dedup_by` to merge some auxiliary information from removed elements into kept elements, I was surprised to observe that `vec.dedup_by(same_bucket)` calls `same_bucket(a, b)` where `b` appears before `a` in the vector, and discards `a` when true is returned. This argument order is probably a bug, but since it has already been stabilized, I guess we should document it as a feature and move on. (`Vec::dedup` also uses `==` with this unexpected argument order, but I figure that’s not important since `==` is expected to be symmetric with no side effects.)