title: Language-Ext Unions - Target runtime doesn't support default interface implementation
body: <p>I'm trying to user the Union type in Language-Ext and am getting error: &quot;Target runtime doesn't support default interface implementation&quot; for the method name and &quot;The type or namespace name 'InconsistentFirstName' could not be found&quot;</p>
  <p>My code looks like this:</p>
  <pre><code>[Union]
  public interface Inconsistency
  {
      public Inconsistency InconsistentFirstName(string localValue, string contactCentreValue);
      public Inconsistency InconsistentSurname(string localValue, string contactCentreValue);
  
      public string GetFieldName(Inconsistency inconsistency)
          =&gt; inconsistency switch
          {
              InconsistentFirstName n =&gt; &quot;Name&quot;,
              InconsistenctSurname s =&gt; &quot;Surname&quot;,
              _ =&gt; &quot;&quot;
          };
  }
  </code></pre>