. intro j
  have hsize : (insertUnit (units, assignments, foundContradiction) l).1.size = units.size := by
    simp [insertUnit, h3]
  let j' : Fin (Array.size units) := ⟨j.1, by rw [← hsize]; exact j.2⟩
  exact h2 j'
case h.right
n : Nat
assignments0 : Array Assignment
assignments0_size : assignments0.size = n
units : Array (Literal (PosFin n))
assignments : Array Assignment
assignments_size : assignments.size = n
foundContradiction : Bool
l : Literal (PosFin n)
i : Fin n
i_in_bounds : ↑i < assignments.size
l_in_bounds : l.fst.val < assignments.size
h1 : assignments[↑i] = assignments0[↑i]
h2 : ∀ (j : Fin units.size), ¬units[↑j].fst.val = ↑i
h3 : hasAssignment l.snd assignments[l.fst.val]! = true
⊢ ∀
    (j :
      Fin
        (if hasAssignment l.snd assignments[l.fst.val]! = true then (units, assignments, foundContradiction)
            else
              (units.push (l.fst, l.snd), assignments.modify l.fst.val (addAssignment l.snd),
                foundContradiction || assignments[l.fst.val]! != unassigned)).fst.size),
    ¬units[↑j].fst.val = ↑i
no goals