title: Inferred to have type 'AnyClass', which may be unexpected
body: <p>Here is my code:</p>
  
  <pre><code>if let runningTests = NSClassFromString("XCTestCase") {
      return false
  }
  </code></pre>
  
  <p>The compiler warning: </p>
  
  <blockquote>
    <p>"Constant 'runningTests' inferred to have type 'AnyClass', which may
    be unexpected.</p>
  </blockquote>
  
  <p>What is it I need to cast to to remove this warning without changing my code into a if != nil check on the result of NSClassFromString?</p>