title: Why does hash a not return the same result for a[:b] vs a["b"]?
body: <p>I realize symbol keys in a hash are immutable whereas string keys are mutable, but I still don't understand why that would cause these results ...</p>
  
  <pre><code>[5] pry(main)&gt; a[:b] = "c"
  =&gt; "c"
  [6] pry(main)&gt; a["b"]
  =&gt; nil
  [7] pry(main)&gt; a[:b]
  =&gt; "c"
  </code></pre>
  
  <p>Shouldn't <code>"a[:b]"</code> get turned into <code>a["b"]</code> under the hood?</p>