title: Why is readonly array assignable to numeric dictionary?
body: <p>I am wondering why TS allows assigning readonly arrays to numeric dictionaries.</p>
  
  <pre class="lang-js prettyprint-override"><code>const x: readonly string[] = []
  const y: { [key: number]: string } = x
  y[0] = 'asd' // this is unwanted behavior
  </code></pre>
  
  <p>I would expect a TS error on second line (assigning to y). However the code passes with no errors.</p>