Disclaimer: As this is a purely code style proposal my opinion is solely based on my personal code style preferences and what I personally find "readable" or not.

What is your evaluation of the proposal?

-1

Is the problem being addressed significant enough to warrant a change to Swift?

I personally don't see significant improvement compared with what can be done already, on the other side it introduces new way of specifying parameters to functions.

Trailing closure is already a controversial syntactic sugar, which is as well not applicable in all the cases, i.e. it's not allowed in if-else and other control statements as conflicts with the syntax to define code blocks, and I don't see yet how proposed solution will address this, so the feature will be still limited.

Also I'm personally against Xcode suggesting trailing closures by default as was mentioned before, this imposes particular code style and at least could be configured with code editor settings. I constantly find myself fighting this and trying to avoid using trailing closure where I don't want it. Even with this feature I don't think I will be keen on using trailing closures like that, I'd prefer to pass parameters to the functions in one clear way.

Even with simple things like map, filter etc. functions where trailing closure feature fits well (maybe?) in my experience I find myself more and more not using it as instead I use more functional constructs like filter(equals(otherValue)) or map(\.keyPath) which does not require different syntax for passing closure parameters.

Formatting issues mentioned in alternatives section of the proposal would be better solved with automatic code formatting improvements in Xcode or other formatting tools rather than introducing new syntactic sugar that does not really simplify writing code enough in my opinion.

It's fair to say that extra brackets and other syntax elements only add noise but the proposal does not decrease this noise significantly.

I'm also concerned that this adds unnecessary complexity to parsing such code with any 3rd party tool as it adds yet another variation, where single trailing closure is already complex enough case. For instance how this will affect working with SwiftSyntax?

Does this proposal fit well with the feel and direction of Swift?

If the direction is to rely more and more on {} then I feel we will end up with Swift becoming some other language.

If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?

not that I'm aware of

How much effort did you put into your review? A glance, a quick reading, or an in-depth study?

read the proposal