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Scala宏注释错误的解决方法

scala-macro-paradise scala-macros scala

1

Mateusz Kubuszok · 技术社区 · 7 年前

我有一个宏注释,用于将隐式类型类注入到伴随方法中。

@MyMacro case class MyClass[T](a: String, b: Int, t: T)

@MyMacro case class MyClass[T: TypeClass](a: String, b: Int, t: T)
// private[this] not allowed for case class parameters

described on SO 和 reported as a bug .

...(implicit tc: TypeClass[T]) .

1 回复 | 直到 7 年前

1

ä½æ°æ°´ 6 年前

class AnnotationType() extends scala.annotation.StaticAnnotation {
  def macroTransform(annottees: Any*): Any = macro AnnotationTypeImpl.impl
}

class AnnotationTypeImpl(val c: blackbox.Context) {

  import c.universe._

  def impl(annottees: Tree*): Tree = {

    val tree = annottees.head.asInstanceOf[ClassDef]

    val newTree = tree match {
      case ClassDef(mods, name, tparams, impl@Template(parents, self, body)) =>
        val newBody = body.map {
          case ValDef(mods, name, tpt, rhs) =>
            // look here
            // the flag of `private[this]` is Flag.PRIVATE | Flag.LOCAL
            // the flag of `private` is Flag.PRIVATE
            // drop Flag.LOCAL in Modifiers.flags ,  it will change `private[this]` to `private`
            val newMods =
              if(mods.hasFlag(Flag.IMPLICIT))
                mods.asInstanceOf[scala.reflect.internal.Trees#Modifiers].&~(Flag.LOCAL.asInstanceOf[Long]).&~(Flag.CASEACCESSOR.asInstanceOf[Long]).asInstanceOf[Modifiers]
              else
                mods
            ValDef(newMods, name, tpt, rhs)

          case e => e
        }
        ClassDef(mods, name, tparams, Template(parents, self, newBody))
    }
    println(show(tree))
    println(show(newTree))

    q"..${newTree +: annottees.tail}"
  }
}

//试验

@AnnotationType()
case class AnnotationTypeTest[T: Option](a: T){
  def option = implicitly[Option[T]]
}

object AnnotationTypeTest {
  def main(args: Array[String]): Unit = {
    implicit val x = Option(1)

    println(AnnotationTypeTest(100))
    println(AnnotationTypeTest(100).option)
    println(AnnotationTypeTest(100).copy(a =2222))
    println(AnnotationTypeTest(100).copy(a =2222)(Some(999)).option)
  }

}