'as' parameter not compatible to knockout-v3.5 behaviour, or not implemented?

[jensb]

We are using large nested foreach loops in KO templates with 'as', i.e.

<div data-bind="foreach: { data: data, as: 'mydata' }">
    <div data-bind="foreach: { data: data2, as: 'mydata2' }">
         ....
     </div>
 </div>

to be able to refer to parent objects in a simpler way than using $parent and $parents[n].
However, this does not seem to work correctly with Knockout. It executes massively faster (10x and more), but when just replacing foreach with fastForEach in the above example, the loops still get executed (I can see this in the devel console because inside the loop we call custom JS functions) but there is no HTML output, nothing is rendered.

Is this a bug in fastForEach, a missing feature/option (is 'as' implemented at all as a parameter?) or am I missing something obvious?

[jensb]

I created a pull request #53
It works on my end, but I'm not sure if all tests are correct and pass.
Please check and integrate if it works.
Thank you!