> What is your evaluation of the proposal? -0.5 if the annotation is verbose (much longer than @discardable). +0.5 if the annotation is pleasant and concise, like @discardable
> Is the problem being addressed significant enough to warrant a change to > Swift? The warn-by-default behavior is mostly useless. The only reason to make the change is because “if we were designing Swift from scratch, this would probably be a slightly better default”. Most non-void functions are called for their result, and nobody ever forgets to use that result; if they do, it's like if they forgot to call the function altogether — trivial to find, not useful as a compiler diagnostic at all. The new default is better for: - (A) classes that provide both mutating and non-mutating methods; - (B) methods where forgetting to use the result produces a bug (a download task that needs to be resumed, an alert that needs to be displayed, a listener that needs to be stored somewhere, etc). The old default is better for: - (C) fluid APIs and other similar DSL scenarios; - (D) methods that are mainly invoked for their side effect and return a value “just in case”, like removing/adding elements, scheduling tasks, ... I've just scanned the entire Swift codebase I wrote since that fateful WWDC'14 (~20 kLOC excluding comments and blanks). I only have a handful of classes/methods in each category above, and annotating them one way or another is a trivial matter. Some of them *are not* currently annotated with @warn_unused_result, which is a point in favor of this proposal. > Does this proposal fit well with the feel and direction of Swift? I think the safe-by-default, explicit-opt-out behavior is a better default for Swift, although, like I've said, in practice it doesn't really matter much. Perhaps it's most useful for newcomers; you can easily skip over @warn_unused_result when learning Swift, but you won't be able ignore @discardable. > If you have used other languages or libraries with a similar feature, how do > you feel that this proposal compares to those? Haven't ever seen this in a language. Golang had a (not very informative) discussion on this topic at https://groups.google.com/forum/#!topic/golang-nuts/ksfgSWxJcCo > How much effort did you put into your review? A glance, a quick reading, or > an in-depth study? Closer to an in-depth study; looked at my Swift codebase, and read through all the discussions. On a side note, let me once again point to a dangerous trend in this mailing list: not looking at (or reporting on) how potential changes affect actual, specific, production code bases. We need a lot more of that in our reviews. Thanks, A. _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
