Add a test that dedupeTracked works with EmberObject

[boris-petrov]

cc @chriskrycho

[chriskrycho]

@boris-petrov it's failing on the lint stage – mind updating accordingly? Thanks!

[chriskrycho]

I haven't had time to dig into the details here, but here's an intuitive explanation of what's happening based on what I see in the stack trace:

1. Decorators¹ work by doing a defineProperty call in the constructor, just like class fields do, but with all the extra hooks for actually doing the right things as decorated properties.
2. Ember object initialization does its very best to interoperate correctly with that (see in particular its check for whether what it gets back is a descriptor).

Best guess is that what this is currently returning is incompatible with how Ember expects a descriptor to come back (missing a name, maybe?). That's all I have at the moment.

Footnotes

1. under the current spec, at least; I don't remember if the semantics are the same under the updated proposal which is being presented at TC39 this month ↩

[boris-petrov]

I don't remember why I had this use case. I now don't so for me this is low priority. If someone has the time, they could try to see what's going on. If not, still fine. :) Let's just leave this PR open and we'll merge it once it passes.