title: Mobx-State-Tree - Assign to Array Type
body: <p>I have this basic model.</p>
  <pre><code>const stuff = types.model({
    term: types.string,
    excludeTerm: types.string,
    stores: types.array(types.string)
  }).actions(self =&gt; ({
    setTerm(term: string) {
      self.term = term
    },
    setExcludeTerm(term: string) {
      self.excludeTerm = term
    },
    setStores(stores: string[]) {
      self.stores = stores   // &lt;&lt;&lt; the lint error is on this line
    }
  }))
  </code></pre>
  <p>I get the following TS Lint error:</p>
  <blockquote>
  <p>Type 'string[]' is not assignable to type 'IMSTArray&lt;ISimpleType&gt; &amp; IStateTreeNode&lt;IArrayType&lt;ISimpleType&gt;&gt;'.
  Type 'string[]' is missing the following properties from type 'IMSTArray&lt;ISimpleType&gt;': spliceWithArray, observe, intercept, clear, and 4 more.ts(2322)</p>
  </blockquote>
  <p>This is an annoying error. I can fix it by assigning like this: <code>(self as any).stores = stores</code> but I want to stop doing hacks to my code.</p>
  <p>The question is why I get this error? Is there another way to assign to an array type in mobx-state-tree?</p>
  <p>I couldn't find in mobx-state-tree a more detailed documenation for working with arrays. Does anyone know any?</p>