check_opaque

# File lib/uri/generic.rb, line 531
    def check_opaque(v)
      return v unless v

      # raise if both hier and opaque are not nil, because:
      # absoluteURI   = scheme ":" ( hier_part | opaque_part )
      # hier_part     = ( net_path | abs_path ) [ "?" query ]
      if @host || @port || @user || @path  # userinfo = @user + ':' + @password
        raise InvalidURIError, 
          "can not set opaque with host, port, userinfo or path"
      elsif v && OPAQUE !~ v
        raise InvalidComponentError,
          "bad component(expected opaque component): #{v}"
      end

      return true
    end