title: Scaladoc fails to generate links for inner classes in method and class signatures
body: <p>I have a top level trait that contains a number of classes and traits like:</p>
  
  <pre><code>trait Trees { self: Types =&gt;
    trait Tree
    trait IdentifiedTree extends Tree
    trait Empty extends Tree
  
    /** The factory for [[TypeUse]] instances */
    trait TypeUse extends Tree
    /** AST tree to represent erroneous trees */
    object BadTree extends IdentifiedTree
    /** AST tree for empty statements and trees */
    val Empty: Empty = new Empty {}
  }
  
  trait Types
  </code></pre>
  
  <p>When I generate the documentation for it, using scaladoc I can link to the inner classes, using [[CLASS_NAME]], but scaladoc fails to create links for trees both in signatures and extends.</p>
  
  <p>I use sbt to generate the scaladoc, and I use the following flags:</p>
  
  <pre><code>scalacOptions in (Compile, doc) ++= Seq("-groups", "-implicits",
       "-diagrams", "-no-prefixes", "-author", "-explaintypes",
       "-language:implicitConversions,higherKinds")
  </code></pre>
  
  <p>To give you a better idea, the api for the above definition is as follows (please note the missing links):</p>
  
  <p><img src="https://i.stack.imgur.com/uAgHM.png" alt="enter image description here"></p>
  
  <p>Can you tell me what am I doing wrong, please?</p>