title: How does association between Directory and Property/Variable work in WiX?
body: <p>In Wix (3.11) there seems to be an implicit link between a  with the Id 'ProgramFilesFolder' and the 'ProgramFilesFolder' variable.  That is, a directory with that id will be named according to the property value.</p>
  
  <p>When I try replicating this on my own with a "Test" directory:</p>
  
  <pre><code>&lt;Property Id="Test" Value="Test"/&gt;
  
  &lt;Directory Id="TARGETDIR" Name="SourceDir"&gt;
    &lt;Directory Id="ProgramFilesFolder"&gt;
       &lt;Directory Id="Test"/&gt;
         ...
  </code></pre>
  
  <p>I get a warning from WiX, and the installer actually hangs.  I've also tried declaring "Test" as a WixVariable, but in that case it appeared the  element was simply ignored - iow, no "Test" folder was created.</p>
  
  <p>My question is how does this implicit link work for WiX variables, but not for my own?</p>