在打字稿中扩展typeof常量？

Question

此代码返回错误：

case TOGGLE_BANK: {
  const mode: modes =
    state.mode === smoothPianoKit ? initialState.mode : smoothPianoKit;
  return {
    ...state,
    bank: !state.bank,
    bankMode: mode,
    mode: mode
  };
}

我具有此接口属性，我想在其中结合其类型，即模式中的bankModeTypes：

export const heaterKit = 'Heater Kit';
export const smoothPianoKit = 'Smooth Piano Kit';
export const heater1 = 'Heater-1';
export type bankModeTypes = typeof heaterKit | typeof smoothPianoKit;
export type modes = bankModeTypes  | typeof heater1
export interface DrumMachineState {
  bankMode: bankModeTypes;
  mode: modes | bankModeTypes;
}

如您所见，smoothPianoKit是bankModeTypes，在我包括它的模式上，或者为什么这不起作用？我不想用任何东西。