class RuboCop::Cop::Style::EachWithObject

def accumulator_param_assigned_to?(body, args)

then we can't convert to each_with_object
if the accumulator parameter is assigned to in the block, 
def accumulator_param_assigned_to?(body, args)
  first_arg, = *args
  accumulator_var, = *first_arg
  body.each_descendant.any? do |n|
    next unless n.assignment?
    lhs, _rhs = *n
    lhs.equal?(accumulator_var)
  end
end