(motive : MProd (Array (Lean.TSyntax `Lean.Parser.Term.matchAltExpr)) ℕ → Sort u_1) →
  (r : MProd (Array (Lean.TSyntax `Lean.Parser.Term.matchAltExpr)) ℕ) →
    ((alts : Array (Lean.TSyntax `Lean.Parser.Term.matchAltExpr)) → (ctorIdx : ℕ) → motive ⟨alts, ctorIdx⟩) → motive r