* What is your evaluation of the proposal?
-1. I would much rather see it either as an operator, or more likely as some other special syntax/meaning in Swift.
* Is the problem being addressed significant enough to warrant a change to Swift?
No. Providing backwards compatibility with a single library that used an undocumented feature is not a significant enough reason.
* Does this proposal fit well with the feel and direction of Swift?
* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
I read the proposal and previous reviews.