title: Mapstruct with abstract and wildcard
body: <p>I have the following code :</p>
  
  <pre><code>public class EntityA {
    private List&lt;? extends AbstractObject&gt; objects;
  }
  
  public class EntityB {
    private List&lt;? extends AbstractObjectDTO&gt; dtos;
  }
  </code></pre>
  
  <p>I have a generic mapper :</p>
  
  <pre><code>public interface GenericMapper&lt;X extends AbstractObjectDTO, Y extends AbstractObject&gt; {
  
    Y mapDTOToEntity(X value);
  
    X mapEntityToDTO(Y value);
  }
  
  @Mapper
  public interface ConcreteMapper extends GenericMapper&lt;ConcreteDTO, ConcreteObject&gt; {}
  </code></pre>
  
  <p>At compile time it generates the following error :
  <strong>Can't map property "<code>List&lt;? extends AbstractObject&gt;</code> objects" to "<code>List&lt;? extends AbstractObjectDTO&gt;</code> dtos". Consider to declare/implement a mapping method: "<code>List&lt;? extends AbstractObjectDTO&gt; map(List&lt;? extends AbstractObject&gt; value)</code>".</strong></p>
  
  <p>And when I do implement the map method as shown in the error I have the following error :
  <strong>Can't generate mapping method for a generic type variable source.</strong></p>
  
  <p>How to map the lists properly ?</p>