ADT derivation can produce not the same code between compilation

[Romastyi]

During Decoder/Codec derivation for ADT subclasses additional values declaration by indexes are using (here and here):

    val (transformedNameNames: List[TermName], transformedNameDefs: List[Tree]) = subclassList.zipWithIndex.map {
      case (s, i) =>
        val name = TermName(s"name$i")
        val value = transformName(nameOf(s))
        (name, q"private[this] val $name = $value")
    }.unzip

Despite that subclassList in both cases is defined as (here and here):

    // We don't _really_ care about the order but want to be sure its stable here.
    val subclassList: List[Symbol] = subclasses.toList

this implementation does not guarantee the same order (in fact, stable indexes) of such definitions between several compilations of the same code.