未找到Scala：值宏 [英] Scala not found: value macro

问题描述

此行：

"foo".assertNonFatal( _ equals "foo", "error message");

此错误：

Error:(120, 47) not found: value assertion

final implicit class ImplicitAssert[MyType](val me: MyType) {

  final def assertNonFatal(assertion: (MyType) => Boolean, message: String)
    : MyType = macro ImplicitAssertMacros.assertNonFatal[MyType]
}

此宏：

object ImplicitAssertMacros {
  def assertNonFatal[MyType](c: scala.reflect.macros.blackbox.Context)
      (assertion: c.Tree, message: c.Tree): c.Tree = {
    import c.universe._
    val me = q"${c.prefix}.me" // "me" from ImplicitAssert class.
    val numLines = q"Int.MaxValue"
    val useStdOut = q"false"
    val assertionTrue = q"assertion($me)"
    val isFatal = q"false"
    val toReturn = q"""
       _root_.info.collaboration_station.debug.internal.Printer.traceInternalAssert($message, $numLines, $useStdOut, $assertionTrue, $isFatal);
       $me;
    """
    toReturn
  }
}

^我不知道这个编译器错误的原因是什么或如何解决它。

^ I can't figure out what the cause of this compiler error is or how to fix it.

请注意，只有在编译源文件而不是宏时才会发生。

Note that it only happens when I compile the source file, not the macros.

推荐答案

它的工作原理是：

val assertionTrue = q"$assertion($me)"

def宏会在调用网站展开，其中不再有任何断言参数。

A def macro expands at the call site, where there is no longer any assertion parameter.

这篇关于未找到Scala：值宏的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！