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        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Nested calculations using intermediate CSS Custom Properties don't work"
   href="https://bugs.webkit.org/show_bug.cgi?id=161002">161002</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Nested calculations using intermediate CSS Custom Properties don't work
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>Safari Technology Preview
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Macintosh
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>OS X 10.11
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>CSS
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>sgomes&#64;google.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>As per example 9 in section 2.2 (Resolving Dependency Cycles) of the spec (<a href="https://drafts.csswg.org/css-variables/">https://drafts.csswg.org/css-variables/</a>), it should be possible to have nested calculations:

one   { --foo: 10px; }
two   { --bar: calc(var(--foo) + 10px); }
three { --foo: calc(var(--bar) + 10px); }

This doesn't seem to work in Safari 9.1.2 or Safari Technology Preview.

Furthermore, it is stated: &quot;Custom properties are left almost entirely unevaluated, except that they allow and evaluate the var() function in their value.&quot;
This implies that it should be possible to declare the intermediate calculations without calc() as well, as the value returned by var() would just be substituted into the new definition.

I have prepared a demo illustrating both ways of nesting calculations; one using calc() for the intermediate steps (as per the example above), and one using calc() for the final step only: <a href="http://codepen.io/anon/pen/bZJaVO">http://codepen.io/anon/pen/bZJaVO</a>
The expected result is that the third div in both groups is 30px wide.

Steps to reproduce:
1 - Load <a href="http://codepen.io/anon/pen/bZJaVO">http://codepen.io/anon/pen/bZJaVO</a>
2 - Observe third div in each group

Expected results: third div should be 30px wide.

Actual results: third div is 10px wide in Safari 9.1.2; third div fits to screen width in Safari Technology Preview.

Other browsers: The demo produces the expected result in both Chrome 53 and Firefox 48.</pre>
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