// @flow import { Actions, type Action } from './actions' export type State = { count: number, other: string, } const initialState: State = { count: 0, other: 'test' } export default function(state: State = initialState, action: Action): State { switch (action.type) { case Actions.INCREMENT: return { ...state, counter: state.count + 1 } default: return state } } 一見正しいように見えます。 flowの型エラーはでません。 しかし、よ