cases b <;> simp
case hi.succ.hc
n : ℕ
b : Bool
n✝ : ℕ
hb : succ n✝ = 0 → b = true
ih : size (succ n✝) ≤ log 2 (succ n✝) + 1
⊢ (bif b then 1 else 0) < 2

case hi.succ
n : ℕ
b : Bool
n✝ : ℕ
hb : succ n✝ = 0 → b = true
ih : size (succ n✝) ≤ log 2 (succ n✝) + 1
⊢ bit b (succ n✝) ≠ 0
case hi.succ
n : ℕ
b : Bool
n✝ : ℕ
hb : succ n✝ = 0 → b = true
ih : size (succ n✝) ≤ log 2 (succ n✝) + 1
⊢ bit b (succ n✝) ≠ 0