(motive : Lean.IR.Alt → Sort u_1) →
  (x : Lean.IR.Alt) →
    ((i : Lean.IR.CtorInfo) → (b : Lean.IR.FnBody) → motive (Lean.IR.Alt.ctor i b)) →
      ((b : Lean.IR.FnBody) → motive (Lean.IR.Alt.default b)) → motive x