title: Polly: wrap AsyncFallbackPolicy<TResult> with AsyncFallbackPolicy
body: <p>I want to wrap a combination of <code>AsyncFallbackPolicy &lt;- AsyncFallbackPolicy&lt;bool&gt; &lt;- AsyncRetryPolicy</code>.</p>
  
  <p>Wrapping <code>AsyncFallbackPolicy&lt;bool&gt; &lt;- AsyncRetryPolicy</code> works fine and the resulting PolicyWrap is <code>AsyncPolicyWrap&lt;bool&gt;</code>. But as soon as I add AsyncFallbackPolicy I get the following error:</p>
  
  <blockquote>
    <p>You have executed the generic .Execute method on a
    non-generic FallbackPolicy.  A non-generic FallbackPolicy only defines
    a fallback action which returns void; it can never return a substitute
    TResult value.  To use FallbackPolicy to provide fallback TResult
    values you must define a generic fallback policy
    FallbackPolicy.  For example, define the policy as
    Policy.Handle.Fallback(/* some TResult
    value or Func&lt;..., TResult> */);</p>
  </blockquote>
  
  <p>I execute the policy via <code>await policyWrap.ExecuteAsync(async () =&gt; await ...</code></p>
  
  <p>I couldn't figure out how to resolve this issue. Is it possible to wrap like that? If yes, how?</p>
  
  <p>Thanks</p>