title: mobx-state-tree literal array
body: <p>is it possible to create literal array type in MST? It should be an equivalent to </p>
  
  <p><code>type Interval = ['1min', '5min']</code>;</p>
  
  <p>here is an example of code which throw an error </p>
  
  <pre><code>type Interval = '1min' | '5min';
  
  export interface AppStore {
    config: {
      intervals: ['1min', '5min']
    },
    search: {
      symbol: string;
      interval: string;
      dataTypes: string[];
    }
  }
  
  const appStore = types
    .model&lt;AppStore&gt;('appStore', {
      config: types.model({
        intervals: types.array(
          types.literal&lt;Interval&gt;('1min'),
          types.literal&lt;Interval&gt;('5min')
        ),
      }),
      search: types.model({
        dataTypes: types.array( types.string ),
        interval: types.union(
          types.literal&lt;Interval&gt;('1min'),
          types.literal&lt;Interval&gt;('5min')
        ),
        symbol: types.string,
      }),
    })
  </code></pre>
  
  <p>the <code>types.array()</code> expect to have one argument so is it even possible? No luck with MST documentation <a href="https://github.com/mobxjs/mobx-state-tree#types-overview" rel="nofollow noreferrer">https://github.com/mobxjs/mobx-state-tree#types-overview</a></p>