Question

假设我有一个宏注释AnnProxy和以下代码：

trait MyTrait
{
  def x: Int
}

@AnnProxy
class MyClass extends MyTrait

我现在需要获取MyTrait的类型，以便我可以代理它的方法。到目前为止，我的代码看起来像：

@compileTimeOnly("enable macro paradise to expand macro annotations")
class AnnProxy extends StaticAnnotation
{
    def macroTransform(annottees: Any*): Any = macro IdentityMacro.impl
}

object IdentityMacro
{
  def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
    import c.universe._

    val inputs = annottees.map(_.tree).toList

    val classDef = inputs.head.asInstanceOf[ClassDef]
    val superclass= // how do I get the Type of the superclass?

    c.Expr[Any] {
        q"""
      class ${classDef.name} {
        def doit() : Unit = println("doit")
      }
  """
    }
}
}

Answer 1

你可以使用模式匹配

class SuperClass extends StaticAnnotation {
  def macroTransform(annottees: Any*): Any = macro SuperClassImpl.apply

}

class SuperClassImpl(val c: Context) {

  def showInfo(s: String) =
    c.info(c.enclosingPosition, s.split("\n").mkString("\n |---macro info---\n |", "\n |", ""), true)

  import c.universe._

  def apply(annottees: c.Expr[Any]*) = {

    val superClass = annottees.map(_.tree).head match {
      case q"$mod class $name(..$params) extends ..$superClass { ..$body }" =>
        superClass
    }

    showInfo(show(superClass))
    q"{..$annottees}"
  }
}

测试

trait AA
trait BB
trait CC
@SuperClass
class SuperClassUsing extends AA with BB with CC //when show info List(AA,BB,CC)

获取宏注释的tparam的类型

1 个答案: