Scala不是一个封闭类。

Question

编写此规范时：

import org.specs.Specification
import org.specs.matcher.extension.ParserMatchers

class ParserSpec extends Specification with ParserMatchers {
  type Elem = Char

  "Vaadin DSL parser" should {
    "parse attributes in parentheses" in {
      DslParser.attributes must(
        succeedOn(stringReader("""(attr1="val1")""")).
          withResult(Map[String, AttrVal]("attr1" -> AttrVal("val1", "String"))))
    }
  }
}

I get the following error:

ParserSpec.scala:21
error: scala is not an enclosing class
withResult(Map[String, AttrVal]("attr1" -> AttrVal("val1", "String"))))
           ^

我完全不理解这里的错误信息。为什么会出现这种情况？

Scala 版本为 2.8.1，specs 版本为 1.6.7.2。

DslParser.attributes 的类型为 Parser[Map[String, AttrVal]]，并且组合器 succeedOn 和 withResult 定义如下：

trait ParserMatchers extends Parsers with Matchers {
  case class SucceedOn[T](str: Input,
                          resultMatcherOpt: Option[Matcher[T]]) extends Matcher[Parser[T]] {
    def apply(parserBN: => Parser[T]) = {
      val parser = parserBN
      val parseResult = parser(str)
      parseResult match {
        case Success(result, remainingInput) =>
          val succParseMsg = "Parser "+parser+" succeeded on input "+str+" with result "+result
          val okMsgBuffer = new StringBuilder(succParseMsg)
          val koMsgBuffer = new StringBuilder(succParseMsg)
          val cond = resultMatcherOpt match {
            case None =>
              true
            case Some(resultMatcher) =>
              resultMatcher(result) match {
                case (success, okMessage, koMessage) =>
                  okMsgBuffer.append(" and ").append(okMessage)
                  koMsgBuffer.append(" but ").append(koMessage)
                  success
              }
          }
          (cond, okMsgBuffer.toString, koMsgBuffer.toString)
        case _ =>
          (false, "Parser succeeded", "Parser "+parser+": "+parseResult)
      }
    }

    def resultMust(resultMatcher: Matcher[T]) = this.copy(resultMatcherOpt = Some(resultMatcher))

    def withResult(expectedResult: T) = resultMust(beEqualTo(expectedResult))

    def ignoringResult = this.copy(resultMatcherOpt = None)
  }

  def succeedOn[T](str: Input, expectedResultOpt: Option[Matcher[T]] = None) =
    SucceedOn(str, expectedResultOpt)

  implicit def stringReader(str: String): Reader[Char] = new CharSequenceReader(str)
}

- Alexey Romanov

Answer 1

这个消息可能出现在编译器试图发出类型错误或类型推断失败的情况下。这是scalac中的一个错误（或错误组）。

为了定位问题，请逐步添加显式类型和类型参数；将复杂表达式分解成较小的子表达式。

如果您能提供一个单独的示例并提交错误报告，那就更好了。

- retronym