title: Android data binding attribute not found
body: <p>I am trying to replicate this answer: <a href="https://stackoverflow.com/questions/9013298/setting-attribute-of-child-element-of-included-layout/44691776#44691776">Setting attribute of child element of included layout</a></p>
  
  <p>I have a simple <code>custom_edit_text.xml</code>:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;layout
      xmlns:android="http://schemas.android.com/apk/res/android"&gt;
      &lt;data&gt;
          &lt;variable name="hint123" type="String" /&gt;
      &lt;/data&gt;
      &lt;android.support.design.widget.TextInputLayout
          android:id="@+id/emailInputLayout"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"&gt;
          &lt;android.support.v7.widget.AppCompatEditText
              android:id="@+id/emailField"
              android:layout_width="275dp"
              android:layout_height="wrap_content"
              android:paddingBottom="16dp"
              android:paddingTop="14dp"
              android:hint="@{hint123}"
              android:textCursorDrawable="@null"
              android:background="@drawable/edit_text_background"
              android:fontFamily="@font/eina_regular"
              android:textColor="@color/edit_text_color"
              android:textColorHint="@color/edit_text_color"
              android:textSize="15sp"
              /&gt;
      &lt;/android.support.design.widget.TextInputLayout&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <p>And I include it in another file:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;layout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"&gt;
      &lt;include
              layout="@layout/custom_edit_text"
              app:hint123="Email"/&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <p>However the project refuses to compile after a clean &amp; rebuild with the error:</p>
  
  <p><code>AAPT: error: attribute hint123 (aka inc.company.appname:hint123) not found.</code></p>
  
  <p>Any ideas?</p>
  
  <p>I also have </p>
  
  <pre><code>dataBinding {
      enabled = true
  }
  </code></pre>
  
  <p>enabled in the app level <code>build.gradle</code></p>