fun findTypeInList (ts : T.t list) (l : string list) (f : string) =
    let val fieldTypes = ListPair.zipEq(l, ts)
        val fieldTypeOpt = List.find(fn (f',_) => f = f') fieldTypes
    in
      #2 (Option.valOf fieldTypeOpt)
    end

fun traversePath (t : T.t) (path : string list)
    case path of
      [] => t
    | x::xs => let val T.$(TO.Struct l, [ts]) = T.out t
               in traversePath (findTypeInList ts l x) xs
               end