title: Unexpected behavior accessing keyword list using `ìn`
body: <p>In my template (<code>html.eex</code> file) I'm trying to use a keyword list to pass options. I have:</p>
  
  <pre><code>&lt;%= if :layer1 in @buttonCSS do %&gt;&lt;%= @buttonCSS[:layer1] %&gt;&lt;% end %&gt;
  </code></pre>
  
  <p>Then, I pass values like this where I use my template:</p>
  
  <pre><code>&lt;%= render MyProject.ComponentView, "button.html",
      buttonCSS: [layer1: "font-style: italic;"]
  %&gt;
  </code></pre>
  
  <p>If I don't use the <code>if</code> condition this works.
  So, shouldn't <code>in</code> work here?</p>
  
  <p>I've tried to just use <code>layer1</code> instead of <code>:layer1</code> but then I have an error.</p>
  
  <p>PS: Also, why using <code>.layer1</code> instead of <code>[:layer1]</code> doesn't work?</p>