title: Maven Java Version Configuration ignored by Eclipse/Idea
body: <p>I have:</p>
  
  <pre><code>&lt;build&gt;
    &lt;pluginManagement&gt;
       &lt;plugins&gt;
          &lt;plugin&gt;
             &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
             &lt;artifactId&gt;maven-compiler-plugin&lt;/artifactId&gt;
             &lt;version&gt;3.1&lt;/version&gt;
             &lt;configuration&gt;
                &lt;source&gt;1.6&lt;/source&gt;
                &lt;target&gt;1.6&lt;/target&gt;
             &lt;/configuration&gt;
          &lt;/plugin&gt;
       &lt;/plugins&gt;
    &lt;/pluginManagement&gt;
  &lt;/build&gt;
  </code></pre>
  
  <p>Yet I have no problem declaring:</p>
  
  <pre><code>public enum DirectoryWatchService {
  
      INSTANCE;
  
      private java.util.Optional&lt;String&gt; test;
      private java.nio.file.Files files;
  }
  </code></pre>
  
  <p>Eclipse doesn't bother. IntelliJ neither. Even Maven does not bother. 
  I can even do a <em>mvn clean package</em>. Builds the darn thing without any warning whatsoever. </p>