Google Closure Compiler coerce type from EventTarget to Node

Question

I'm trying to compile my program which has a click event listener on an image and I am trying to check to see if that click happened on a particular element or on some other element.

function(e){
    var img_wrapper = goog.dom.getElementsByClass('imgWrapper');
    if (img_wrapper.length > 0 &&  goog.dom.findCommonAncestor(e.target, img_wrapper[0]) === img_wrapper[0]){
        return;
    }
}

When I compile, I get this error:

flickr_closure.js:226: WARNING - actual parameter 1 of goog.dom.findCommonAncestor does not match formal parameter
found   : (EventTarget|null)
required: (Node|null|undefined)
  if (img_wrapper.length > 0 &&  goog.dom.findCommonAncestor(e.target, img_wrapper[0]) === img_wrapper[0]){
                                                         ^

0 error(s), 1 warning(s), 97.0% typed

The code works like I want it to, but I still get that warning, and since this is for a school assignment, one of the requirements is that I can't have warnings when compiled.

I've tried adding some basic type information for e.target to try to tell the compiler to treat it as a Node, but it complains about that too.

Answer 1

Use so-called type-casting:

/** @type {Node} */ (e.target)

e.g.

goog.dom.findCommonAncestor(/** @type {Node} */ (e.target), img_wrapper[0])

Answer 2

Expanding on Alex's answer, it is good practise to type-cast after actually checking the variable.

if(goog.dom.isElement(e.target)) {
  .... /** @type {!Element} */ (e.target) ....
}