"No Instance of type variable R exist so that Observable conforms to Observable" Error when updating to RxJava2
<p>I am trying to make a call to API using <code>retrofit and rxJava</code>. The code below seems to work well when using <code>RxJava 1</code>, but once I updated to <code>RxJava 2</code> I am getting this error: </p>

<p><strong>Error :</strong> </p>

<blockquote>
  <p>No Instance of type variable R exist so that Observable conforms to
  Observable</p>
</blockquote>

<p><strong>Api</strong> </p>

<pre><code>Observable&lt;HttpResult&lt;List&lt;Article&gt;&gt;&gt; getList(@Query("key")String key);
</code></pre>

<p>Api request done here, and this is where I get this error inside <code>.map</code> operator </p>

<pre><code>Observable cache=providers.getList().map(new HttpRsltFunc&lt;List&lt;Article&gt;&gt;());
</code></pre>

<p><strong>Result class model :</strong></p>

<pre><code>private  class HttpRsltFunc&lt;T&gt; implements Func1&lt;HttpResult&lt;T&gt;, T&gt; {
       @Override
       public T call(HttpResult&lt;T&gt; httpResult) {   
           return httpResult.getData();
       }
   }
</code></pre>

<p><strong>Edit :</strong> </p>

<p>When importing <code>rx.Observable</code> instead of <code>io.reactivex.Observable</code> the code works just fine.</p>

<p>Thank you</p>