{motive_1 : Lean.Widget.HighlightedMsgEmbed → Sort u} →
  (ctorIdx : ℕ) →
    (t : Lean.Widget.HighlightedMsgEmbed) →
      ctorIdx = t.ctorIdx → Lean.Widget.HighlightedMsgEmbed.ctorElimType ctorIdx → motive_1 t