-- Mathlib/Data/QPF/Multivariate/Constructions/Cofix.lean
theorem Cofix.bisim {α : TypeVec n} (r : Cofix F α → Cofix F α → Prop)
    (h : ∀ x y, r x y → LiftR (RelLast α r (i := _)) (Cofix.dest x) (Cofix.dest y)) :
    ∀ x y, r x y → x = y

Proof state:
case h
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
⊢ (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Tactic:
rcases (liftR_iff (fun a b => RelLast α r a b) (dest x) (dest y)).mp (h x y rxy)
  with ⟨a, f₀, f₁, dxeq, dyeq, h'⟩

Result:
case h.intro.intro.intro.intro.intro
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
⊢ (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Proof state:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h.fs
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
i : Fin2 n
j : (P F).B a i.fs
⊢ f₀ i.fs j = f₁ i.fs j

Tactic:
apply h' _ j

Result:
no goals

Proof state:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h.fs
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
i : Fin2 n
j : (P F).B a i.fs
⊢ splitFun (dropFun f₀) (Quot.mk r ∘ lastFun f₀) i.fs j = splitFun (dropFun f₁) (Quot.mk r ∘ lastFun f₁) i.fs j

Tactic:
change f₀ _ j = f₁ _ j

Result:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h.fs
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
i : Fin2 n
j : (P F).B a i.fs
⊢ f₀ i.fs j = f₁ i.fs j

Proof state:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
⊢ ∀ (x y : Cofix F α), r x y → x = y

Tactic:
apply Cofix.bisim_rel

Result:
case h
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
⊢ ∀ (x y : Cofix F α), r x y → (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Proof state:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h.fz
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
j : (P F).B a Fin2.fz
⊢ splitFun (dropFun f₀) (Quot.mk r ∘ lastFun f₀) Fin2.fz j = splitFun (dropFun f₁) (Quot.mk r ∘ lastFun f₁) Fin2.fz j

Tactic:
apply Quot.sound

Result:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h.fz.a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
j : (P F).B a Fin2.fz
⊢ r (lastFun f₀ j) (lastFun f₁ j)

Proof state:
case h.intro.intro.intro.intro.intro
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
⊢ (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Tactic:
rw [dxeq, dyeq, ← abs_map, ← abs_map, MvPFunctor.map_eq, MvPFunctor.map_eq]

Result:
case h.intro.intro.intro.intro.intro
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
⊢ MvQPF.abs ⟨a, (TypeVec.id ::: Quot.mk r) ⊚ f₀⟩ = MvQPF.abs ⟨a, (TypeVec.id ::: Quot.mk r) ⊚ f₁⟩

Proof state:
case h
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
⊢ ∀ (x y : Cofix F α), r x y → (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Tactic:
intro x y rxy

Result:
case h
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
⊢ (TypeVec.id ::: Quot.mk r) <$$> x.dest = (TypeVec.id ::: Quot.mk r) <$$> y.dest

Proof state:
case h.intro.intro.intro.intro.intro
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
⊢ MvQPF.abs ⟨a, splitFun (dropFun f₀) (Quot.mk r ∘ lastFun f₀)⟩ =
    MvQPF.abs ⟨a, splitFun (dropFun f₁) (Quot.mk r ∘ lastFun f₁)⟩

Tactic:
congr 2 with (i j)

Result:
case h.intro.intro.intro.intro.intro.e_a.e_snd.a.h
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
r : Cofix F α → Cofix F α → Prop
h : ∀ (x y : Cofix F α), r x y → LiftR (fun {i} => α.RelLast r) x.dest y.dest
x y : Cofix F α
rxy : r x y
a : (P F).A
f₀ f₁ : (P F).B a ⟹ fun {i} => (α ::: Cofix F α) i
dxeq : x.dest = MvQPF.abs ⟨a, f₀⟩
dyeq : y.dest = MvQPF.abs ⟨a, f₁⟩
h' : ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.RelLast r (f₀ i j) (f₁ i j)
i : Fin2 (n + 1)
j : (P F).B a i
⊢ splitFun (dropFun f₀) (Quot.mk r ∘ lastFun f₀) i j = splitFun (dropFun f₁) (Quot.mk r ∘ lastFun f₁) i j