forwardable.rb

  def self._delegator_method(obj, accessor, method, ali)
    accessor = accessor.to_s unless Symbol === accessor

    if Module === obj ?
         obj.method_defined?(accessor) || obj.private_method_defined?(accessor) :
         obj.respond_to?(accessor, true)
      accessor = "#{accessor}()"
    end

    method_call = ".__send__(:#{method}, *args, &block)"
    if _valid_method?(method)
      loc, = caller_locations(2,1)
      pre = "_ ="
      mesg = "#{Module === obj ? obj : obj.class}\##{ali} at #{loc.path}:#{loc.lineno} forwarding to private method "
      method_call = "#{<<-"begin;"}\n#{<<-"end;".chomp}"
        begin;
          unless ::Kernel.instance_method(:respond_to?).bind(_).call(:"#{method}")
            ::Kernel.warn "\#{caller_locations(1)[0]}: "#{mesg.dump}"\#{_.class}"'##{method}'
            _#{method_call}
          else
            _.#{method}(*args, &block)
          end
        end;
    end

    _compile_method("#{<<-"begin;"}\n#{<<-"end;"}", __FILE__, __LINE__+1)
    begin;
      proc do
        def #{ali}(*args, &block)
          #{pre}
          begin
            #{accessor}
          end#{method_call}#{FILTER_EXCEPTION}
        end
      end
    end;
  end