title: Error when building: error[E0283]: type annotations needed in Rust
body: <p>I'm trying to understand why I'm getting this error:</p>
  <blockquote>
  <p>error[E0283]: type annotations needed
  this method call resolves to <code>T</code>
  cannot infer type for type parameter <code>S</code> declared on the associated function <code>count</code></p>
  </blockquote>
  <p>There is a library that has this method:</p>
  <pre><code>pub fn count&lt;'a, S: Display + Into&lt;Cow&lt;'a, str&gt;&gt;&gt;(&amp;self, name: S, val: i64, tags: Vec&lt;String&gt;)
  </code></pre>
  <p>And in the main code there is a call of this method:</p>
  <pre><code>self.metrics.count(teststring.into(), 1, vec![]);
  </code></pre>
  <p>How this issue can be resolved?</p>