emberjs/ember.js — pull request #4220 by hjdivad (2014-01-23 23:52:16+00:00)
Title: Improve `reduceComputed` array check assertion.

In #4078 the problem is that `reduceComputed` cannot be used against
non-extended native arrays as we cannot `addArrayObserver`. `reduceComputed`
used to inform users of this, but no longer does so since support for
non-array dependent keys. This commit corrects this grievous error.

Fix #4078

cc @alexspeller