Theorem: Finset.sumLift₂_eq_empty
File: Mathlib/Data/Sum/Interval.lean

Proof steps:
state_before: α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
a : α₁ ⊕ α₂
b : β₁ ⊕ β₂
c : γ₁ ⊕ γ₂
⊢ sumLift₂ f g a b = ∅ ↔
    (∀ (a₁ : α₁) (b₁ : β₁), a = inl a₁ → b = inl b₁ → f a₁ b₁ = ∅) ∧
      ∀ (a₂ : α₂) (b₂ : β₂), a = inr a₂ → b = inr b₂ → g a₂ b₂ = ∅
state_after: case refine_1
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
a : α₁ ⊕ α₂
b : β₁ ⊕ β₂
c : γ₁ ⊕ γ₂
h : sumLift₂ f g a b = ∅
⊢ (∀ (a₁ : α₁) (b₁ : β₁), a = inl a₁ → b = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), a = inr a₂ → b = inr b₂ → g a₂ b₂ = ∅

case refine_2
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
a : α₁ ⊕ α₂
b : β₁ ⊕ β₂
c : γ₁ ⊕ γ₂
h :
  (∀ (a₁ : α₁) (b₁ : β₁), a = inl a₁ → b = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), a = inr a₂ → b = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g a b = ∅
tactic: refine ⟨fun h ↦ ?_, fun h ↦ ?_⟩
state_before: case refine_2
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
a : α₁ ⊕ α₂
b : β₁ ⊕ β₂
c : γ₁ ⊕ γ₂
h :
  (∀ (a₁ : α₁) (b₁ : β₁), a = inl a₁ → b = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), a = inr a₂ → b = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g a b = ∅
state_after: case refine_2.inl.inl
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
c : γ₁ ⊕ γ₂
val✝¹ : α₁
val✝ : β₁
h :
  (∀ (a₁ : α₁) (b₁ : β₁), inl val✝¹ = inl a₁ → inl val✝ = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), inl val✝¹ = inr a₂ → inl val✝ = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g (inl val✝¹) (inl val✝) = ∅

case refine_2.inl.inr
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
c : γ₁ ⊕ γ₂
val✝¹ : α₁
val✝ : β₂
h :
  (∀ (a₁ : α₁) (b₁ : β₁), inl val✝¹ = inl a₁ → inr val✝ = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), inl val✝¹ = inr a₂ → inr val✝ = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g (inl val✝¹) (inr val✝) = ∅

case refine_2.inr.inl
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
c : γ₁ ⊕ γ₂
val✝¹ : α₂
val✝ : β₁
h :
  (∀ (a₁ : α₁) (b₁ : β₁), inr val✝¹ = inl a₁ → inl val✝ = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), inr val✝¹ = inr a₂ → inl val✝ = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g (inr val✝¹) (inl val✝) = ∅

case refine_2.inr.inr
α₁ : Type u_1
α₂ : Type u_2
β₁ : Type u_3
β₂ : Type u_4
γ₁ : Type u_5
γ₂ : Type u_6
f f₁ g₁ : α₁ → β₁ → Finset γ₁
g f₂ g₂ : α₂ → β₂ → Finset γ₂
c : γ₁ ⊕ γ₂
val✝¹ : α₂
val✝ : β₂
h :
  (∀ (a₁ : α₁) (b₁ : β₁), inr val✝¹ = inl a₁ → inr val✝ = inl b₁ → f a₁ b₁ = ∅) ∧
    ∀ (a₂ : α₂) (b₂ : β₂), inr val✝¹ = inr a₂ → inr val✝ = inr b₂ → g a₂ b₂ = ∅
⊢ sumLift₂ f g (inr val✝¹) (inr val✝) = ∅
tactic: cases a <;> cases b