useReducerでなぜかエラー

import { Users } from "config/userList"
import { useReducer } from 'react'

type User = {
  Id: number,
  Image: string,
  Name: string,
  DoClap: number,
  ReciveClap: number,
}

const initialState: User = {...Users[0]};

enum UserActionType {
  SET = "SET"
}

type UserAction = {
  type: UserActionType;
  res?: User;
}

const set = (res: User) => ({
  type: UserActionType.SET,
  res
})

const reducer = (state, action: UserAction) => {
  switch (action.type) {
    case UserActionType.SET:
      return [action.res]
    default:
      state;
  }
}

export const getUser = () => {
  const [state, dispatch] = useReducer(reducer, initialState); //ここでエラーは発生して

  const handleSelect = e => {
    dispatch(set(e.target.value));
  }

  return [state, handleSelect];
}

下記のようなエラーが発生します。

No overload matches this call.
  Overload 1 of 5, '(reducer: ReducerWithoutAction<any>, initializerArg: any, initializer?: undefined): [any, DispatchWithoutAction]', gave the following error.
    Argument of type '(state: any, action: UserAction) => (User | undefined)[] | undefined' is not assignable to parameter of type 'ReducerWithoutAction<any>'.
  Overload 2 of 5, '(reducer: (state: any, action: UserAction) => (User | undefined)[] | undefined, initialState: (User | undefined)[] | undefined, initializer?: undefined): [...]', gave the following error.
    Argument of type 'User' is not assignable to parameter of type '(User | undefined)[]'.

エラーの内容で調べても全く歯が立たない状態です.
もし可能であれば、ご教授お願いします。