cases t with | mk val r children =>
cases r
. cases bt with | mk rt =>
  simp at rt
  generalize eq : (children.nodes) = ts
  rw[eq] at rt
  cases rt
  . simp
    apply rank_zero_IsRankedTree
    assumption
. simp_arith
α : Sort ?u.144314
le : α → α → Bool
not_le_le : ∀ (x y : α), ¬le x y = true → le y x = true
le_trans : ∀ (x y z : α), le x y = true → le y z = true → le x z = true
le_rfl : ∀ (z : α), le z z = true
α✝ : Type u_1
t : BinTree α✝
bt : IsBinTree t
⊢ 0 < t.rank
no goals