class RuboCop::Cop::Style::ParallelAssignment::AssignmentSorter

Newer versions have a better API, but that doesn’t help us
Helper class necessitated by silly design of TSort prior to Ruby 2.1

def accesses?(rhs, lhs)

Does `rhs` access the same value which is assigned by `lhs`?
`lhs` is an assignment method call like `obj.attr=` or `ary[idx]=`. 
def accesses?(rhs, lhs)
  if lhs.method?(:[]=)
    matching_calls(rhs, lhs.receiver, :[]).any? do |args|
      args == lhs.arguments
    end
  else
    access_method = lhs.method_name.to_s.chop.to_sym
    matching_calls(rhs, lhs.receiver, access_method).any?
  end
end

def dependency?(lhs, rhs) 

def dependency?(lhs, rhs)
  uses_var?(rhs, var_name(lhs)) ||
    lhs.send_type? && lhs.assignment_method? && accesses?(rhs, lhs)
end

def initialize(assignments) 

def initialize(assignments)
  @assignments = assignments
end

def tsort_each_child(assignment) 

def tsort_each_child(assignment)
  # yield all the assignments which must come after `assignment`
  # (due to dependencies on the previous value of the assigned var)
  my_lhs, _my_rhs = *assignment
  @assignments.each do |other|
    _other_lhs, other_rhs = *other
    next unless dependency?(my_lhs, other_rhs)
    yield other
  end
end

def tsort_each_node 

def tsort_each_node
  @assignments.each { |a| yield a }
end