simp only [bind_assoc, pure_bind]
case h
α : Type u
m : Type v → Type w
inst✝¹ : Monad m
β : Type v
inst✝ : LawfulMonad m
f : α → m β
x✝ : Array α
a✝ a : α
x : Array α
IH :
  mapM f (push x a✝) = do
    let y ← mapM f x
    let b ← f a✝
    pure (push y b)
b : β
⊢ (do
      let y ←
        do
          let y ← mapM f x
          let b ← f a✝
          pure (push y b)
      pure (cons b y)) =
    do
    let x ← mapM f x
    let y ← pure (cons b x)
    let b ← f a✝
    pure (push y b)
case h
α : Type u
m : Type v → Type w
inst✝¹ : Monad m
β : Type v
inst✝ : LawfulMonad m
f : α → m β
x✝ : Array α
a✝ a : α
x : Array α
IH :
  mapM f (push x a✝) = do
    let y ← mapM f x
    let b ← f a✝
    pure (push y b)
b : β
⊢ (do
      let x ← mapM f x
      let x_1 ← f a✝
      pure (cons b (push x x_1))) =
    do
    let x ← mapM f x
    let b_1 ← f a✝
    pure (push (cons b x) b_1)