case mp =>
  rintro ⟨h,rfl⟩
  refine ⟨_,?_,rfl⟩
  simpa using h
n : Nat
α : Type u_1
f : Fin n → α
i : Nat
x : α
⊢ (∃ h, f { val := i, isLt := ⋯ } = x) → ∃ a, (∃ h, { val := i, isLt := ⋯ } = a) ∧ f a = x
no goals