-- Mathlib/Data/Ordmap/Ordset.lean
theorem balance_eq_balance' {l x r} (hl : Balanced l) (hr : Balanced r) (sl : Sized l)
    (sr : Sized r) : @balance α l x r = balance' l x r

Proof state:
case pos.node.node
α : Type u_1
x : α
ls : ℕ
lx : α
rs : ℕ
rl : Ordnode α
rx : α
rr : Ordnode α
hr : (node rs rl rx rr).Balanced
sr : (node rs rl rx rr).Sized
h : ¬delta * ls < rs
h_1 : delta * rs < ls
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
lrs : ℕ
lrl : Ordnode α
lrx : α
lrr : Ordnode α
hl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Balanced
sl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Sized
ld : delta ≤ (node lls lll llx llr).size + (node lrs lrl lrx lrr).size
⊢ (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).rotateR x (node rs rl rx rr) =
    rec nil
      (fun size l x_1 r l_ih r_ih =>
        rec nil
          (fun size_1 l x_2 r l_ih r_ih =>
            if size_1 < ratio * size then
              node (ls + rs + 1) (node lls lll llx llr) lx
                (node (size_1 + rs + 1) (node lrs lrl lrx lrr) x (node rs rl rx rr))
            else
              node (ls + rs + 1) (node (size + l.size + 1) (node lls lll llx llr) lx l) x_2
                (node (r.size + rs + 1) r x (node rs rl rx rr)))
          (node lrs lrl lrx lrr))
      (node lls lll llx llr)

Tactic:
dsimp [rotateR]

Result:
case pos.node.node
α : Type u_1
x : α
ls : ℕ
lx : α
rs : ℕ
rl : Ordnode α
rx : α
rr : Ordnode α
hr : (node rs rl rx rr).Balanced
sr : (node rs rl rx rr).Sized
h : ¬delta * ls < rs
h_1 : delta * rs < ls
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
lrs : ℕ
lrl : Ordnode α
lrx : α
lrr : Ordnode α
hl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Balanced
sl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Sized
ld : delta ≤ (node lls lll llx llr).size + (node lrs lrl lrx lrr).size
⊢ (if lrs < ratio * lls then (node lls lll llx llr).node3R lx (node lrs lrl lrx lrr) x (node rs rl rx rr)
    else (node lls lll llx llr).node4R lx (node lrs lrl lrx lrr) x (node rs rl rx rr)) =
    if lrs < ratio * lls then
      node (ls + rs + 1) (node lls lll llx llr) lx (node (lrs + rs + 1) (node lrs lrl lrx lrr) x (node rs rl rx rr))
    else
      node (ls + rs + 1) (node (lls + lrl.size + 1) (node lls lll llx llr) lx lrl) lrx
        (node (lrr.size + rs + 1) lrr x (node rs rl rx rr))

Proof state:
case pos
α : Type u_1
x : α
ls : ℕ
lx : α
hr : nil.Balanced
sr : nil.Sized
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
lrs : ℕ
lrl : Ordnode α
lrx : α
lrr : Ordnode α
hl : ((node lls lll llx llr).node' lx (node lrs lrl lrx lrr)).Balanced
sl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Sized
h✝ : lrs < ratio * lls
⊢ lls + (lrs + 1) = lls + lrs + 1

Tactic:
abel

Result:
no goals

Proof state:
case nil.node.nil.node.refl
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx : α
rrs : ℕ
rrx : α
rrr : Ordnode α
hr : (nil.node' rx (node rrs nil rrx rrr)).Balanced
sr : (node rs nil rx (node rrs nil rrx rrr)).Sized
this : nil.size = 0 ∧ rrr.size = 0
⊢ node 3 (Ordnode.singleton x) rx (node rrs nil rrx rrr) =
    if 0 + (0 + rrs + 1) ≤ 1 then nil.node' x (nil.node' rx (node rrs nil rrx rrr))
    else
      if 0 + rrs + 1 > 0 then nil.rotateL x (nil.node' rx (node rrs nil rrx rrr))
      else nil.node' x (nil.node' rx (node rrs nil rrx rrr))

Tactic:
cases sr.2.2.2.2.size_eq_zero.1 this.2

Result:
case nil.node.nil.node.refl.refl
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx : α
rrs : ℕ
rrx : α
hr : (nil.node' rx (node rrs nil rrx nil)).Balanced
sr : (node rs nil rx (node rrs nil rrx nil)).Sized
this : nil.size = 0 ∧ nil.size = 0
⊢ node 3 (Ordnode.singleton x) rx (node rrs nil rrx nil) =
    if 0 + (0 + rrs + 1) ≤ 1 then nil.node' x (nil.node' rx (node rrs nil rrx nil))
    else
      if 0 + rrs + 1 > 0 then nil.rotateL x (nil.node' rx (node rrs nil rrx nil))
      else nil.node' x (nil.node' rx (node rrs nil rrx nil))

Proof state:
case neg
α : Type u_1
x : α
ls : ℕ
lx : α
rs : ℕ
rl : Ordnode α
rx : α
rr : Ordnode α
hr : (node rs rl rx rr).Balanced
sr : (node rs rl rx rr).Sized
h : ¬delta * ls < rs
h_1 : delta * rs < ls
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
lrs : ℕ
lrl : Ordnode α
lrx : α
lrr : Ordnode α
hl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Balanced
sl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Sized
ld : delta ≤ (node lls lll llx llr).size + (node lrs lrl lrx lrr).size
h✝ : ¬lrs < ratio * lls
⊢ (node lls lll llx llr).node4R lx (node lrs lrl lrx lrr) x (node rs rl rx rr) =
    node (ls + rs + 1) (node (lls + lrl.size + 1) (node lls lll llx llr) lx lrl) lrx
      (node (lrr.size + rs + 1) lrr x (node rs rl rx rr))

Tactic:
simp [node4R, node', sl.1, sl.2.2.1]

Result:
case neg
α : Type u_1
x : α
ls : ℕ
lx : α
rs : ℕ
rl : Ordnode α
rx : α
rr : Ordnode α
hr : (node rs rl rx rr).Balanced
sr : (node rs rl rx rr).Sized
h : ¬delta * ls < rs
h_1 : delta * rs < ls
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
lrs : ℕ
lrl : Ordnode α
lrx : α
lrr : Ordnode α
hl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Balanced
sl : (node ls (node lls lll llx llr) lx (node lrs lrl lrx lrr)).Sized
ld : delta ≤ (node lls lll llx llr).size + (node lrs lrl lrx lrr).size
h✝ : ¬lrs < ratio * lls
⊢ lls + lrl.size + 1 + (lrr.size + rs + 1) = lls + (lrl.size + lrr.size + 1) + 1 + rs

Proof state:
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx : α
rls : ℕ
rll : Ordnode α
rlx : α
rlr : Ordnode α
hr : ((node rls rll rlx rlr).node' rx nil).Balanced
sr : (node rs (node rls rll rlx rlr) rx nil).Sized
⊢ rll.size = 0 ∧ rlr.size = 0

Tactic:
have := balancedSz_zero.1 hr.1

Result:
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx : α
rls : ℕ
rll : Ordnode α
rlx : α
rlr : Ordnode α
hr : ((node rls rll rlx rlr).node' rx nil).Balanced
sr : (node rs (node rls rll rlx rlr) rx nil).Sized
this : (node rls rll rlx rlr).size ≤ 1
⊢ rll.size = 0 ∧ rlr.size = 0

Proof state:
case node.nil.node.nil
α : Type u_1
x : α
ls : ℕ
lx : α
hr : nil.Balanced
sr : nil.Sized
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
hl : ((node lls lll llx llr).node' lx nil).Balanced
sl : (node ls (node lls lll llx llr) lx nil).Sized
⊢ node 3 (node lls lll llx llr) lx (Ordnode.singleton x) =
    if lls + 1 ≤ 1 then ((node lls lll llx llr).node' lx nil).node' x nil
    else
      if lls + 1 > 0 then ((node lls lll llx llr).node' lx nil).rotateR x nil
      else ((node lls lll llx llr).node' lx nil).node' x nil

Tactic:
have : size lll = 0 ∧ size llr = 0 := by
  have := balancedSz_zero.1 hl.1
  rwa [size, sl.2.1.1, Nat.succ_le_succ_iff, Nat.le_zero, add_eq_zero] at this

Result:
case node.nil.node.nil
α : Type u_1
x : α
ls : ℕ
lx : α
hr : nil.Balanced
sr : nil.Sized
lls : ℕ
lll : Ordnode α
llx : α
llr : Ordnode α
hl : ((node lls lll llx llr).node' lx nil).Balanced
sl : (node ls (node lls lll llx llr) lx nil).Sized
this : lll.size = 0 ∧ llr.size = 0
⊢ node 3 (node lls lll llx llr) lx (Ordnode.singleton x) =
    if lls + 1 ≤ 1 then ((node lls lll llx llr).node' lx nil).node' x nil
    else
      if lls + 1 > 0 then ((node lls lll llx llr).node' lx nil).rotateR x nil
      else ((node lls lll llx llr).node' lx nil).node' x nil

Proof state:
case nil.node.nil.node.refl.refl.hc
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx rrx : α
this : nil.size = 0 ∧ nil.size = 0
hr : (nil.node' rx (node 1 nil rrx nil)).Balanced
sr : (node rs nil rx (node 1 nil rrx nil)).Sized
⊢ nil.size < ratio * (node 1 nil rrx nil).size

Tactic:
dsimp only [size]

Result:
case nil.node.nil.node.refl.refl.hc
α : Type u_1
x : α
hl : nil.Balanced
sl : nil.Sized
rs : ℕ
rx rrx : α
this : nil.size = 0 ∧ nil.size = 0
hr : (nil.node' rx (node 1 nil rrx nil)).Balanced
sr : (node rs nil rx (node 1 nil rrx nil)).Sized
⊢ 0 < ratio * 1