title: Android databinding: cannot find ...BindingImpl in generated databinding file
body: <p>I am trying to databind a viewmodel using the example project android-sunflower. The current issue is that when I am trying to build the project I get the error <code>error: cannot find symbol symbol:   class FragmentShopBindingImpl
    location: package {{packageName}}.databinding</code> in the class <code>DataBindinMapperImpl</code>
  I'm not really sure what I am missing here, since I added everything from the example project. The class <code>FragmentShopBindingImpl</code> does not get generated, or shouldn't it? Since I cannot see any occurence of a class ending with 'Impl' in the android sunflower example<br>
  My code: </p>
  
  <pre><code>override fun onCreateView(
          inflater: LayoutInflater, container: ViewGroup?,
          savedInstanceState: Bundle?
      ): View? {
  
          val factory = InjectorUtils.provideShopViewModelFactory(context!!)
          val shopViewModel = ViewModelProviders.of(this, factory)
              .get(ShopViewModel::class.java)
  
          val binding = DataBindingUtil.inflate&lt;FragmentShopBinding&gt;(
              inflater, R.layout.fragment_shop, container, false).apply {
              viewModel = shopViewModel
              lifecycleOwner = this@ShopFragment
          }
  
          return binding.root
      }
  </code></pre>
  
  <p>Layout: </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;layout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"&gt;
  
      &lt;data&gt;
          &lt;variable
              name="viewModel"
              type="{{packageName}}.viewmodel.ShopViewModel" /&gt;
      &lt;/data&gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:orientation="vertical"
          tools:context=".fragments.ShopFragment"&gt;
  
          &lt;TextView
              android:text="@{viewModel}"
              android:layout_width="match_parent"
              android:layout_height="match_parent" /&gt;
  
      &lt;/LinearLayout&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <p>Image of generated file (ignore the {{packageName}}:</p>
  
  <p><a href="https://i.stack.imgur.com/LmKeL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/LmKeL.png" alt="enter image description here"></a></p>