title: form_for method using slim
body: <p>I have looked at the documentation of slim, and I still can't figure out how to do this in slim:</p>
  
  <pre><code>&lt;%= form_for([@post, @post.comments.build]) do |f| %&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :commenter %&gt;&lt;br /&gt;
      &lt;%= f.text_field :commenter %&gt;
    &lt;/div&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :body %&gt;&lt;br /&gt;
      &lt;%= f.text_area :body %&gt;
    &lt;/div&gt;
    &lt;div class="actions"&gt;
      &lt;%= f.submit %&gt;
    &lt;/div&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>I try to translate the first line like this</p>
  
  <pre><code>= form_for([@post, @post.reviews.build]) do |f|
  </code></pre>
  
  <p>But I am getting a syntax error.</p>