key == this.key -> key.java.cast(value)
      else -> next[key]
    }

  /** Returns a [toString] consistent with [Map], with elements in insertion order. */
  override fun toString(): String =
    generateSequence<LinkedTags<*>>(seed = this) { it.next as? LinkedTags<*> }
      .toList()
      .reversed()
      .joinToString(prefix = "{", postfix = "}") { "${it.key}=${it.value}" }
}