title: I'm prevented from using a switch statement that doesn't cover all possible cases
body: <pre><code>return degrees % 90 != 0? Optional.empty() : Optional.of( switch( degrees ) {
              case 0 -&gt; NORTH;
              case 90 -&gt; EAST;
              case 180 -&gt; SOUTH;
              case 270 -&gt; WEST;
              //default -&gt; null;  is there something I can put here to make empty Optional?
          } );
  </code></pre>
  <p>Above returns an Optional containing an enum of the cardinal directions. The code has previously ensured that these are the only 4 possible values of <code>degrees</code>. But IntelliJ IDEA won't allow this, complaining that the <code>switch</code> hasn't handled all possible values.
  I've searched for a <code>@SuppressWarnings</code> annotation to allow this; the closest I've found is <code>SwitchStatementWithoutDefaultBranch</code>, but it doesn't help.</p>
  <p>It seems like there should be an annotation that would allow this.</p>
  <p>I know the code can be rewritten to work around the issue, but why can't this be handled?</p>