使用宏获取Scala类的实现类型

import scala.reflect.macros.whitebox.Context
import scala.language.experimental.macros
import scala.annotation.StaticAnnotation

class GetImplementationType extends StaticAnnotation {
  def macroTransform(annottees: Any*): Any = macro GetImplementationTypeMacro.impl
}

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

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

    val outputs = inputs match {
      case (classDef: ClassDef) :: rest =>
        val className = classDef.name
        val classType = tq"$className"
        val implementationType = tq"${className.toTypeName}Impl"
        val companionObject = q"object $className { type ImplementationType = $implementationType }"
        val updatedClassDef = q"$classDef { type ImplementationType = $implementationType }"

        companionObject :: updatedClassDef :: rest

      case _ =>
        c.abort(c.enclosingPosition, "Annotation can only be applied to classes")
    }

    c.Expr[Any](Block(outputs, Literal(Constant(()))))
  }
}

@GetImplementationType
class MyClass {
  // class implementation
}

class MyClass {
  type ImplementationType = MyClassImpl
}

object MyClass {
  type ImplementationType = MyClassImpl
}