class Rufo::Formatter

def visit_op_assign(node)
  # target += value
  #
  # [:opassign, target, op, value]
  _, target, op, value = node
  line = @line
  visit target
  consume_space
  # [:@op, "+=", [1, 2]],
  check :on_op
  before = op[1][0...-1]
  after = op[1][-1]
  write before
  track_assignment before.size
  write after
  next_token
  visit_assign_value value
  @assignments_ranges[line] = @line if @line != line
end