{motive : Lean.Grind.AC.StartsWithResult✝ → Sort u} →
  (t : Lean.Grind.AC.StartsWithResult✝¹) →
    Lean.Grind.AC.StartsWithResult.ctorIdx✝ t = 0 → motive Lean.Grind.AC.StartsWithResult.false✝ → motive t