class RuboCop::Cop::Lint::StringConversionInInterpolation

def on_dstr(node)
  node.children.select { |n| n.type == :begin }.each do |begin_node|
    final_node = begin_node.children.last
    next unless final_node && final_node.type == :send
    receiver, method_name, *args = *final_node
    next unless method_name == :to_s && args.empty?
    add_offense(
      final_node,
      :selector,
      receiver ? MSG_DEFAULT : MSG_SELF
    )
  end
end