∀ {α : Type u_1} [inst : BEq α] [inst_1 : LawfulBEq α] {xs : List α} {xc : (x : α) × Fin (List.count x xs)},
  List.countBefore xs[↑(xs.sigmaCountToIdx xc)] xs ↑(xs.sigmaCountToIdx xc) <
    (List.findIdxs (fun x => x == xc.fst) xs).length