Module: Mathlib.Combinatorics.Matroid.Sum

Goal state before:
pp: case refine_3
ι : Type u_1
α : ι → Type u_2
M : (i : ι) → Matroid (α i)
I X : Set ((i : ι) × α i)
hI : ∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' I)
x✝ :
  (∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X) ∧
    (∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t) ∧
      ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
hIX : ∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X
h' : ∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t
h'' : ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
⊢ I ⊆ X

pp: case refine_4
ι : Type u_1
α : ι → Type u_2
M : (i : ι) → Matroid (α i)
I X : Set ((i : ι) × α i)
hI : ∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' I)
x✝ :
  (∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X) ∧
    (∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t) ∧
      ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
hIX : ∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X
h' : ∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t
h'' : ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
⊢ ∀ ⦃t : Set ((i : ι) × α i)⦄, (∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' t)) → t ⊆ X → I ⊆ t → I = t

pp: case refine_5
ι : Type u_1
α : ι → Type u_2
M : (i : ι) → Matroid (α i)
I X : Set ((i : ι) × α i)
hI : ∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' I)
x✝ :
  (∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X) ∧
    (∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t) ∧
      ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
hIX : ∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X
h' : ∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t
h'' : ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
⊢ X ⊆ univ.sigma fun i ↦ (M i).E

Tactic:
· exact fun ⟨i, x⟩ hx ↦ by simpa using hIX i hx

Goal state after:
case refine_4
ι : Type u_1
α : ι → Type u_2
M : (i : ι) → Matroid (α i)
I X : Set ((i : ι) × α i)
hI : ∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' I)
x✝ :
  (∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X) ∧
    (∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t) ∧
      ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
hIX : ∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X
h' : ∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t
h'' : ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
⊢ ∀ ⦃t : Set ((i : ι) × α i)⦄, (∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' t)) → t ⊆ X → I ⊆ t → I = t

case refine_5
ι : Type u_1
α : ι → Type u_2
M : (i : ι) → Matroid (α i)
I X : Set ((i : ι) × α i)
hI : ∀ (i : ι), (M i).Indep (Sigma.mk i ⁻¹' I)
x✝ :
  (∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X) ∧
    (∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t) ∧
      ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
hIX : ∀ (x : ι), Sigma.mk x ⁻¹' I ⊆ Sigma.mk x ⁻¹' X
h' : ∀ (x : ι) ⦃t : Set (α x)⦄, (M x).Indep t → t ⊆ Sigma.mk x ⁻¹' X → Sigma.mk x ⁻¹' I ⊆ t → Sigma.mk x ⁻¹' I = t
h'' : ∀ (x : ι), Sigma.mk x ⁻¹' X ⊆ (M x).E
⊢ X ⊆ univ.sigma fun i ↦ (M i).E