build.properties

sbt.version=1.4.7

build.sbt

scalaVersion := "3.0.0-RC1"

Main.scala

import scala.deriving.Mirror
import scala.compiletime.{erasedValue, summonInline}

object Macros {

  inline def values[A](using inline A: Mirror.SumOf[A]): List[A] =
    summonValues[A.MirroredElemTypes].asInstanceOf[List[A]]

  inline def summonValues[T <: Tuple]: List[Any] =
    inline erasedValue[T] match {
      case _: EmptyTuple => 
        Nil
      case _: (t *: ts) =>
        summonInline[ValueOf[t]].value :: summonValues[ts]
    }
}

sealed trait A
case object B extends A
case object C extends A
case object D extends A

object Main {
  def main(args: Array[String]): Unit = {
    val x = Macros.values[A]
    println(x)
    assert(x.toSet == Set(B, C, D))
  }
}

plugins.sbt

addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.3")