title: Can anyone explain Swift Combine's Subject.eraseToAnySubject() method and where it should be used?
body: <p>I can see that <code>Subject.eraseToAnySubject()</code> returns the concrete <code>Subject</code> type <code>AnySubject</code>. I'm assuming this is using a type eraser pattern.  </p>
  
  <p>However, the apple docs provide almost no details: <a href="https://developer.apple.com/documentation/combine/passthroughsubject/3241547-erasetoanysubject" rel="nofollow noreferrer">https://developer.apple.com/documentation/combine/passthroughsubject/3241547-erasetoanysubject</a></p>
  
  <p>Can anyone explain how this works and where it should be used?  </p>
  
  <p>Also, would it be possible to use the <code>some</code> keyword to avoid using <code>AnySubject</code>?</p>