Scala软件包问题

我有一个 Words 包含单词类型的包( Noun , Verb , Adjective ...) 但尽管我进口了 Words._ 我的IDE发现每个类都很好,我有一个错误:

Error:(11, 40) type mismatch;
found   : Word (in Words) 
required: Word (in <empty>) 
  val adj: Word = WordFactory.produce("big")

问题是,我的包裹里什么都没有(在 <empty> 包装)。
我正在使用IntelliJ Idea CE。

test("Adjective") {
    val expected: Adjective = Adjective("big", "big", "m", "sp")
    val test: Word = WordFactory.produce("big")
    assert(test == expected)
}

如果我澄清 val test: Words.Word 我的测试失败:

Adjective(big,big,m,sp) did not equal Adjective(big,big,m,sp)
ScalaTestFailureLocation: WordFactoryTests at (WordFactoryTests.scala:13)
Expected :Adjective(big,big,m,sp)
Actual   :Adjective(big,big,m,sp)

形容词
作为参考,我还有其他测试(测试其他用例类,如 名词 )它们是相同的,但效果很好。

问题似乎与scalatest无关,即使在main中,我也有错误(与 <空(>); ).

这是我的文件 Word.scala :

package Words

abstract class Word() {
  val correctWriting: String
  val lemma: String
  var currentWriting: String = correctWriting

  def isCounterfeited: Boolean = this.currentWriting != this.correctWriting

  def counterfeit()
}

Adjective.scala :

package Words

case class Adjective(correctWriting: String, lemma: String, gender: String, number: String) extends Word {
  override def counterfeit: Unit = Counterfeiters.Adjective.counterfeit(this)
}

完整代码已打开 my GitHub .