Statically get the ordinal of any child of a sum-type in Scala

ordinalOf.scala

import scala.compiletime.ops.int.S
import scala.compiletime.constValue
import scala.deriving.Mirror

object Tuples {
  type IndexOf[Q, T <: Tuple, I <: Int] <: Int = T match {
    case EmptyTuple => -1
    case Q *: ts    => I
    case _ *: ts    => IndexOf[Q, ts, S[I]]
  }
}

object Sums {

  inline def ordinalOf[C <: S, S](using m: Mirror.SumOf[S]): Int = {
    type Index = Tuples.IndexOf[C, m.MirroredElemTypes, 0]
    constValue[Index]
  }

}

enum Foo {
  case A
  case B
  case C
}

@main def Test =
  inline def fooOrd[T <: Foo] = Sums.ordinalOf[T, Foo]
  assert(fooOrd[Foo.A.type] == 0)
  assert(fooOrd[Foo.B.type] == 1)
  assert(fooOrd[Foo.C.type] == 2)