class RuboCop::Cop::Style::ParallelAssignment

def find_valid_order(left_elements, right_elements)
  # arrange left_elements in an order such that no corresponding right
  # element refers to a left element earlier in the sequence
  # this can be done using an algorithm called a "topological sort"
  # fortunately for us, Ruby's stdlib contains an implementation
  assignments = left_elements.zip(right_elements)
  begin
    AssignmentSorter.new(assignments).tsort
  rescue TSort::Cyclic
    nil
  end
end