def attachParents(prog: Program, glob: GlobalScope): Unit = {
    for (c <- prog.classes){
      c.parent match{
        case Some(cc) => {
          if (!(glob.classes contains cc.value)){
            fatal("Class "+ cc.value +" inherited from "+ c.id.value +" does not exists at "+c.posString)
          }
          glob.classes.get(c.id.value).get.parent= glob.classes.get(cc.value)
        }
        case _ => {/*no parent*/}
      }
    }
  }

  def attachParents(prog: Program, glob: GlobalScope): Unit = {
    for (c <- prog.classes) c match {
      case ClassDecl(Identifier(id), Some(Identifier(parent)), _, _) => {
        if ((glob.classes contains parent)){
          glob.classes.get(id).get.parent = glob.classes.get(parent)
        }
        else fatal("Class "+ parent +" inherited from "+ id +" does not exists at " + c.posString)
      }
      case _ =>
    }
  }