Fix type inferencing and syntax highlighting for same-unit subclass

[eric-milles]

Consider the following:

class M implements Map {
  @Delegate Map m= [:]
}
class MM extends M {
}

new M ().metaClass = null
new MM().metaClass = null

The second "metaClass" reference works the same as the first, but for some reason highlighting is breaking down.

[eric-milles]