title: Gradle 3.0 "compile" to "implementation" migration doesn't work for fileTree
body: <p>I'm trying to remove all my lint warnings but I'm stuck with one of the <code>compile</code> to <code>implementation</code> migrations.</p>
  
  <p>If I change this:</p>
  
  <pre><code>    compile fileTree(include: ['*.jar'], dir: 'libs')
  </code></pre>
  
  <p>to this:</p>
  
  <pre><code>    implementation fileTree(include: ['*.jar'], dir: 'libs')
  </code></pre>
  
  <p>then the app won't build and I get the following error:</p>
  
  <blockquote>
    <p>Error:Supertypes of the following classes cannot be resolved. Please make sure you have the required dependencies in the classpath: ... unresolved supertypes: veg.mediaplayer.sdk.MediaPlayer.MediaPlayerCallback</p>
  </blockquote>
  
  <p>Is this a bug or am I supposed to do something different for fileTree? I couldn't find any explanations looking at the documentation: <a href="https://developer.android.com/studio/build/gradle-plugin-3-0-0-migration.html" rel="noreferrer">https://developer.android.com/studio/build/gradle-plugin-3-0-0-migration.html</a>.</p>
  
  <p>I've changed all the other lines in all gradle files from <code>compile</code> to <code>implementation</code> and they all work fine.</p>
  
  <p><strong>Edit</strong>: I should also note that this particular module does have a jar in the lib folder. For modules with no jars it works.</p>
  
  <p><strong>Edit 2:</strong> I've noticed that actually it doesn't always happen if there is a jar. I have another module with a jar (that I created) and it works fine. Something must be wrong with the mediaplayersdk.jar.</p>
  
  <p>Given that it's only complaining about the callback that is implemented from a file in the jar, I suppose that is where it's getting stuck.</p>
  
  <p>I also tried with Android Studio 3.1.0-beta1 and gradle 4.4 but it didn't help.</p>