title: How does the ng-invalid-parse class get added to form
body: <p>I am using a custom angular directive for validation of a field in a form. </p>
  
  <p>When one of the validation fails, along with the custom error, the class <code>ng-invalid-parse</code> is also added to the field.</p>
  
  <p>Is it normal behavior?  If so, what causes it?</p>