∀ {n : ℕ} (units : Array (Std.Sat.Literal (Std.Tactic.BVDecide.LRAT.Internal.PosFin n)))
  (assignments : Array Std.Tactic.BVDecide.LRAT.Internal.Assignment) (b : Bool)
  (l : Std.Sat.Literal (Std.Tactic.BVDecide.LRAT.Internal.PosFin n)),
  (Std.Tactic.BVDecide.LRAT.Internal.DefaultFormula.insertUnit (units, assignments, b) l).2.1.size = assignments.size