Module: Mathlib.Topology.Homotopy.Lifting

Goal state before:
pp: case refine_1
E : Type u_1
X : Type u_2
A : Type u_3
inst✝⁴ : TopologicalSpace E
inst✝³ : TopologicalSpace X
inst✝² : TopologicalSpace A
p : E → X
homeo : IsLocalHomeomorph p
inst✝¹ : PathConnectedSpace A
inst✝ : LocallyPathConnectedSpace A
f : C(A, X)
a₀ : A
e₀ : E
he : p e₀ = f a₀
uniq :
  ∀ (γ γ' : C(↑I, A)) (Γ Γ' : C(↑I, E)),
    γ 0 = a₀ →
      γ' 0 = a₀ → Γ 0 = e₀ → Γ' 0 = e₀ → p ∘ ⇑Γ = ⇑(f.comp γ) → p ∘ ⇑Γ' = ⇑(f.comp γ') → γ 1 = γ' 1 → Γ 1 = Γ' 1
Γ : (γ : C(↑I, A)) → γ 0 = a₀ → C(↑I, E)
Γ_0 : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), (Γ γ a) 0 = e₀
Γ_lifts : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), p ∘ ⇑(Γ γ a) = ⇑(f.comp γ)
F : A → E := fun a ↦ (Γ (somePath a₀ a).toContinuousMap ⋯) 1
this : ∀ (a : A), p (F a) = f a
a : A
⊢ ContinuousAt F a

pp: case refine_2
E : Type u_1
X : Type u_2
A : Type u_3
inst✝⁴ : TopologicalSpace E
inst✝³ : TopologicalSpace X
inst✝² : TopologicalSpace A
p : E → X
homeo : IsLocalHomeomorph p
inst✝¹ : PathConnectedSpace A
inst✝ : LocallyPathConnectedSpace A
f : C(A, X)
a₀ : A
e₀ : E
he : p e₀ = f a₀
uniq :
  ∀ (γ γ' : C(↑I, A)) (Γ Γ' : C(↑I, E)),
    γ 0 = a₀ →
      γ' 0 = a₀ → Γ 0 = e₀ → Γ' 0 = e₀ → p ∘ ⇑Γ = ⇑(f.comp γ) → p ∘ ⇑Γ' = ⇑(f.comp γ') → γ 1 = γ' 1 → Γ 1 = Γ' 1
Γ : (γ : C(↑I, A)) → γ 0 = a₀ → C(↑I, E)
Γ_0 : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), (Γ γ a) 0 = e₀
Γ_lifts : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), p ∘ ⇑(Γ γ a) = ⇑(f.comp γ)
F : A → E := fun a ↦ (Γ (somePath a₀ a).toContinuousMap ⋯) 1
this : ∀ (a : A), p (F a) = f a
⊢ { toFun := F, continuous_toFun := ⋯ } a₀ = e₀

pp: case refine_3
E : Type u_1
X : Type u_2
A : Type u_3
inst✝⁴ : TopologicalSpace E
inst✝³ : TopologicalSpace X
inst✝² : TopologicalSpace A
p : E → X
homeo : IsLocalHomeomorph p
inst✝¹ : PathConnectedSpace A
inst✝ : LocallyPathConnectedSpace A
f : C(A, X)
a₀ : A
e₀ : E
he : p e₀ = f a₀
uniq :
  ∀ (γ γ' : C(↑I, A)) (Γ Γ' : C(↑I, E)),
    γ 0 = a₀ →
      γ' 0 = a₀ → Γ 0 = e₀ → Γ' 0 = e₀ → p ∘ ⇑Γ = ⇑(f.comp γ) → p ∘ ⇑Γ' = ⇑(f.comp γ') → γ 1 = γ' 1 → Γ 1 = Γ' 1
Γ : (γ : C(↑I, A)) → γ 0 = a₀ → C(↑I, E)
Γ_0 : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), (Γ γ a) 0 = e₀
Γ_lifts : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), p ∘ ⇑(Γ γ a) = ⇑(f.comp γ)
F : A → E := fun a ↦ (Γ (somePath a₀ a).toContinuousMap ⋯) 1
this : ∀ (a : A), p (F a) = f a
F' : C(A, E)
x✝ : (fun F ↦ F a₀ = e₀ ∧ p ∘ ⇑F = ⇑f) F'
F'_0 : F' a₀ = e₀
hpF' : p ∘ ⇑F' = ⇑f
a : A
⊢ F' a = { toFun := F, continuous_toFun := ⋯ } a

Tactic:
· obtain ⟨p, hep, rfl⟩ := homeo (F a)
    have hfap : f a ∈ p.target := by rw [← this]; exact p.map_source hep
    refine ContinuousAt.congr (f := p.symm ∘ f)
      ((p.continuousAt_symm hfap).comp f.2.continuousAt) ?_
    have ⟨U, ⟨haU, U_conn⟩, hUp⟩ := (path_connected_basis a).mem_iff.mp
      ((p.open_target.preimage f.continuous).mem_nhds hfap)
    refine Filter.mem_of_superset haU fun x hxU ↦ ?_
    have ⟨γ, hγ⟩ := U_conn.joinedIn _ (mem_of_mem_nhds haU) _ hxU
    let Γ' : Path e₀ ((p.symm ∘ f) a) :=
      ⟨Γ _ (somePath a₀ a).source, Γ_0 .., by simp [← this, hep, F]⟩
    specialize uniq ((somePath a₀ a).trans γ) _ (Γ'.trans <| γ.map' <| p.continuousOn_symm.comp
      f.2.continuousOn <| by rintro _ ⟨t, rfl⟩; exact hUp (hγ _)) _ (by simp) (somePath a₀ x).source
      (by simp) (Γ_0 _ (somePath a₀ x).source) _ (Γ_lifts ..) (by simp)
    · ext
      simp only [Function.comp, ContinuousMap.coe_coe, Path.trans_apply, ContinuousMap.coe_comp]
      split_ifs
      · apply congr_fun (Γ_lifts ..)
      · simp [Path.map', p.right_inv (hUp (hγ _))]
    simpa using uniq

Goal state after:
case refine_2
E : Type u_1
X : Type u_2
A : Type u_3
inst✝⁴ : TopologicalSpace E
inst✝³ : TopologicalSpace X
inst✝² : TopologicalSpace A
p : E → X
homeo : IsLocalHomeomorph p
inst✝¹ : PathConnectedSpace A
inst✝ : LocallyPathConnectedSpace A
f : C(A, X)
a₀ : A
e₀ : E
he : p e₀ = f a₀
uniq :
  ∀ (γ γ' : C(↑I, A)) (Γ Γ' : C(↑I, E)),
    γ 0 = a₀ →
      γ' 0 = a₀ → Γ 0 = e₀ → Γ' 0 = e₀ → p ∘ ⇑Γ = ⇑(f.comp γ) → p ∘ ⇑Γ' = ⇑(f.comp γ') → γ 1 = γ' 1 → Γ 1 = Γ' 1
Γ : (γ : C(↑I, A)) → γ 0 = a₀ → C(↑I, E)
Γ_0 : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), (Γ γ a) 0 = e₀
Γ_lifts : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), p ∘ ⇑(Γ γ a) = ⇑(f.comp γ)
F : A → E := fun a ↦ (Γ (somePath a₀ a).toContinuousMap ⋯) 1
this : ∀ (a : A), p (F a) = f a
⊢ { toFun := F, continuous_toFun := ⋯ } a₀ = e₀

case refine_3
E : Type u_1
X : Type u_2
A : Type u_3
inst✝⁴ : TopologicalSpace E
inst✝³ : TopologicalSpace X
inst✝² : TopologicalSpace A
p : E → X
homeo : IsLocalHomeomorph p
inst✝¹ : PathConnectedSpace A
inst✝ : LocallyPathConnectedSpace A
f : C(A, X)
a₀ : A
e₀ : E
he : p e₀ = f a₀
uniq :
  ∀ (γ γ' : C(↑I, A)) (Γ Γ' : C(↑I, E)),
    γ 0 = a₀ →
      γ' 0 = a₀ → Γ 0 = e₀ → Γ' 0 = e₀ → p ∘ ⇑Γ = ⇑(f.comp γ) → p ∘ ⇑Γ' = ⇑(f.comp γ') → γ 1 = γ' 1 → Γ 1 = Γ' 1
Γ : (γ : C(↑I, A)) → γ 0 = a₀ → C(↑I, E)
Γ_0 : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), (Γ γ a) 0 = e₀
Γ_lifts : ∀ (γ : C(↑I, A)) (a : γ 0 = a₀), p ∘ ⇑(Γ γ a) = ⇑(f.comp γ)
F : A → E := fun a ↦ (Γ (somePath a₀ a).toContinuousMap ⋯) 1
this : ∀ (a : A), p (F a) = f a
F' : C(A, E)
x✝ : (fun F ↦ F a₀ = e₀ ∧ p ∘ ⇑F = ⇑f) F'
F'_0 : F' a₀ = e₀
hpF' : p ∘ ⇑F' = ⇑f
a : A
⊢ F' a = { toFun := F, continuous_toFun := ⋯ } a