Trouble with typedefs

[Harbs]

I have an issue with some typedefs and I can’t figure out why a value is being 
minimized.

I created some typedefs for hammer.js: 
https://www.dropbox.com/s/on4cyi02t0tiyue/hammer.swc?dl=0 
<https://www.dropbox.com/s/on4cyi02t0tiyue/hammer.swc?dl=0>

In my app I have the following code:

private static function 
getMouseEventFromHammer(ev:io.github.hammerjs.Event):FakeMouseEvent{
    var mouseEv:FakeMouseEvent = new FakeMouseEvent(ev.type);
    mouseEv.localX = ev.center.x;
    mouseEv.localY = ev.center.y;
    mouseEv.target = ev.target;
    return mouseEv;
}

(FakeMouseEvent is a subclass of MouseEvent which allows setting the target.)

This compiles to:

/**
 * @private
 * @param {io.github.hammerjs.Event} ev
 * @return {com.printui.view.events.FakeMouseEvent}
 */
com.printui.controller.MouseManager.getMouseEventFromHammer = function(ev) {
  var /** @type {com.printui.view.events.FakeMouseEvent} */ mouseEv = new 
com.printui.view.events.FakeMouseEvent(ev.type);
  mouseEv.localX = ev.center.x;
  mouseEv.localY = ev.center.y;
  mouseEv.target = ev.target;
  return mouseEv;
};

which gets minified to:
function V8(a){var b=new 
t_(a.type);b.localX=a.YD.x;b.localY=a.YD.y;b.target=a.target;return b}

Why is center being renamed to YD?

I don’t see the externs for io.github.hammerjs.Event or 
io.github.hammerjs.Center. Isn’t that supposed to be copied somewhere?

Where am I going off?

Harbs