title: Why nested wildcard capture is not possible?
body: <p>I'm struggling to capture a wildcard when it is "nested in another wildcard".
  Is it possible?</p>
  
  <p>The code:</p>
  
  <pre><code>public class ConvolutedGenerics {
  
      // listClass is a class implementing a List of some Serializable type
      public void doSomethingWithListOfSerializables(
              Class&lt;? extends List&lt;? extends Serializable&gt;&gt; listClass) {
  
          // Capture '? extends Serializable' as 'T extends Serializable'
          // The line does not compile with javac 7
          captureTheWildcard(listClass); // &lt;------ zonk here
      }
  
      // listClass is a class implementing a List of some Serializable type
      private &lt;T extends Serializable&gt;
              void captureTheWildcard(
                      Class&lt;? extends List&lt;/* ? extends */T&gt;&gt; listClass) {
  
          // Do something
      }
  }
  </code></pre>
  
  <p>compiled with javac 7 produces:</p>
  
  <pre><code>ConvolutedGenerics.java:18: error: method captureTheWildcard in class ConvolutedGenerics cannot be applied to given types;
                  captureTheWildcard(listClass);
                  ^
    required: Class&lt;? extends List&lt;T&gt;&gt;
    found: Class&lt;CAP#1&gt;
    reason: no instance(s) of type variable(s) T exist so that argument type Class&lt;CAP#1&gt; conforms to formal parameter type Class&lt;? extends List&lt;T&gt;&gt;
    where T is a type-variable:
      T extends Serializable declared in method &lt;T&gt;captureTheWildcard(Class&lt;? extends List&lt;T&gt;&gt;)
    where CAP#1 is a fresh type-variable:
      CAP#1 extends List&lt;? extends Serializable&gt; from capture of ? extends List&lt;? extends Serializable&gt;
  1 error
  </code></pre>
  
  <p>Besides many more simpler cases I've found</p>
  
  <ul>
  <li><a href="https://stackoverflow.com/questions/4459587/incompatible-generic-wildcard-captures">Incompatible generic wildcard captures</a></li>
  <li><a href="https://stackoverflow.com/questions/7485325/using-java-wildcards">Using Java wildcards</a></li>
  </ul>
  
  <p>but I could not infer an answer for my problem from those.</p>