{motive : Lean.Widget.ExprDiffTag✝ → Sort u} →
  (ctorIdx : ℕ) →
    (t : Lean.Widget.ExprDiffTag✝¹) →
      ctorIdx = Lean.Widget.ExprDiffTag.ctorIdx✝ t → Lean.Widget.ExprDiffTag.ctorElimType✝ ctorIdx → motive t