Lean.Syntax →
  ℕ →
    optParam (Array Lean.Meta.AltVarNames) #[] →
      List Lean.Name →
        List Lean.Elab.Tactic.RCases.RCasesPatt →
          Lean.MetaM (Array Lean.Meta.AltVarNames × List (Lean.Name × List Lean.Elab.Tactic.RCases.RCasesPatt))