• What is your evaluation of the proposal?
Well written, concise and to the point. +1 on support for default values as well.
• Is the problem being addressed significant enough to warrant a change to Swift?
Absolutely, not to mention is part of our Generic Manifesto swift/GenericsManifesto.md at main · apple/swift · GitHub and was raised before by Radek Pietruszewski on [SR-115] Support generic constraints in subscripts · Issue #42737 · apple/swift · GitHub
• Does this proposal fit well with the feel and direction of Swift?
Yes, this fits very well with how generic code is written right now.
• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
Quick reading
Regards,
Krzysztof Zabłocki