title: Redux reducer initial state with Typescript
body: <p>I would like to create a reducer with typescript!</p>
  <p><strong>paymentReducer.tsx</strong></p>
  <pre><code>let initialState = {
      saved: [],
  };
  
  export interface Payment {
      saved: ISavedPayment[];
  }
  
  export let payment = (
      state = initialState,
      { type, payload }: PaymentActions
  ): Payment =&gt; {
      switch (type) {
          case SAVED_PAYMENTS_LOADED:
              return { ...state, saved: payload };
          default:
              return state;
      }
  };
  </code></pre>
  <p>No errors! But the type of <code>saved</code> array in <code>state</code> parameter of reducer becomes <code>never</code>. But it should be <code>ISavedPayment[]</code>?</p>
  <blockquote>
  <p><code>(parameter) state: { saved: never[]; }</code></p>
  </blockquote>