(motive : Lean.Parser.LeadingIdentBehavior → Sort u_1) →
  (x : Lean.Parser.LeadingIdentBehavior) →
    (Unit → motive Lean.Parser.LeadingIdentBehavior.default) →
      (Unit → motive Lean.Parser.LeadingIdentBehavior.symbol) →
        (Unit → motive Lean.Parser.LeadingIdentBehavior.both) → motive x