title: UIPinchGestureRecognizer doesn't fire after custom UIGestureRecognizer fails
body: <p>I have a custom <code>UIGestureRecognizer</code> subclass that detects a particular kind of one-finger dragging. On the same scene, I also have a <code>UIPinchGestureRecognizer</code>, that detects two-finger pinches.</p>
  
  <p>The problem happens when the user makes a pinch gesture but puts down one finger an instant before the other: the custom gesture recognizer sees a single touch and engages (sets its state to <code>.began</code>) and the pinch recognizer doesn't. When the second touch is added, the custom recognizer notices and switches its state to <code>.failed</code>. But it's too late and the pinch gesture recognizer doesn't pick it up.</p>
  
  <p>Here's the code for the custom UIGestureRecognizer subclass:</p>
  
  <pre><code>override func touchesBegan(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
      super.touchesBegan(touches, with: event)
      guard touches.count == 1 else {
          state = .failed
          return
      }
      state = .began
  }
  override func touchesMoved(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
      super.touchesMoved(touches, with: event)
      guard touches.count == 1 else {
          state = .failed
          return
      }
      // do gesture recognizer stuff here
  }
  
  override func touchesEnded(_ touches: Set&lt;UITouch&gt;, with event: UIEvent) {
      super.touchesEnded(touches, with: event)
      state = .ended
  }
  </code></pre>
  
  <p>I've tried it with <code>cancelsTouchesInView</code> set to <code>false</code> and with <code>delaysTouchesBegan</code> set to <code>true</code> for the custom gesture recognizer. Neither made a difference in this behavior. </p>
  
  <p>When I use a <code>UIPinchGestureRecognizer</code> with a <code>UIPanGestureRecognizer</code> I don't have this issue, which leads me to think it's not the intended behavior.</p>
  
  <p>What's wrong with my UIGestureRecognizer fail code and how can I fix it so that a UIPinchGestureRecognizer can still recognize pinches where the touches start non-simultaneously?</p>