Reactjs 为什么reducer抛出引用错误？

这是我的第一个版本，但与Next.js不兼容：

import { createReducer } from '../storeUtils';
import { SET_PRODUCT_DEPARTMENTS } from '../actions/productActions';

const initialState = {
  productDepartments: []
};

function setProductDepartments(state, action) {
  return {
    ...state,
    productDepartments: action.payload
  };
}

export default createReducer(initialState, {
  [SET_PRODUCT_DEPARTMENTS]: setProductDepartments
});

在这种情况下，当我编写“下一个构建”时，它抛出以下错误：

ReferenceError: Cannot access 'SET_PRODUCT_DEPARTMENTS' before initialization

但在这种情况下，一切都很好：

import { SET_PRODUCT_DEPARTMENTS } from '../actions/productActions';

const initialState = {
  productDepartments: []
};

const productReducer = (state = initialState, action) => {

    switch (action.type) {
        case SET_PRODUCT_DEPARTMENTS:
            return {
                ...state,
                productDepartments: action.payload
            };

        default:
            return state;
    }
};

export default productReducer;

告诉我这两者之间的问题是什么？