title: "The type Long is not visible" in Eclipse with JDK Compliance 9 and 10
body: <p>With the code provided below, I get the Eclipse error while typing 'The type Long is not visible' (with no further information) on <code>o.get()</code>.</p>
  
  <p>I have the latest JDK installed (Java "11.0.1" 2018-10-16, and using in Eclipse 2018-09 (4.9.0)), and the error only happens when I have the project JDK compliance set to 9 or 10. It does not happen when JDK compliance is set to 1.8 or lower.</p>
  
  <pre><code>import java.util.Optional;
  
  public class TestLongNotVisible {
  
      Optional&lt;Long&gt; o;
  
      void a() {
          long x = o.get();
      }
  
  }
  </code></pre>
  
  <p>I am looking for a fix for this issue. If anyone has experience with this issue or knows the most likely cause, thank you in advance!</p>