{motive : Lean.Server.Overview.MessageOverview✝ → Sort u} →
  (ctorIdx : ℕ) →
    (t : Lean.Server.Overview.MessageOverview✝¹) →
      ctorIdx = Lean.Server.Overview.MessageOverview.ctorIdx✝ t →
        Lean.Server.Overview.MessageOverview.ctorElimType✝ ctorIdx → motive t