Instead of using `fatalError(_:file:line:)` in `default` cases, would a public `unreachable()` function be more efficient?
e.g. <https://github.com/apple/swift/pull/2379> -- Ben > On 3 Oct 2016, at 18:50, João Pinheiro via swift-evolution > <swift-evolution@swift.org> wrote: > > -1 from me too. > > Avoiding having to write "default: break" isn't a good justification to > introduce new syntax. It would make the understanding of case switches harder > without providing any real benefit for the syntax bloat. > > João Pinheiro > > >> On 03 Oct 2016, at 19:41, Xiaodi Wu via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> -1 from me as well. This suggestion falls into the same category as those >> about making `else` optional after `guard`, which is repeatedly rejected. >> Since code is read more often than written, explicit handling of the default >> case never hurts and can increase clarity. Not having to write `default: >> break` offers no help in writing correct code and IMO can't justify new >> syntax or the changing of a well-known control statement. >> >> On Mon, Oct 3, 2016 at 11:39 AM, Robert Widmann via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> -1 in general. I want smarter exhaustiveness analysis, but I don’t want to >> be able to ignore cases that “can’t happen” (so say we, writer of bugs) when >> they’re clearly in the domain of possible values that can be fed to a >> switch-case. Exhaustiveness guarantees wellformedness of a program that >> does happen to go wrong, and makes it much easier to verify the correctness >> of the flow of control of the containing block because all points from the >> switch must be covered. We also don’t have the type-level tools to convince >> the checker to allow you to remove unreachable cases. If it’s really a >> problem that you are writing default cases everywhere, just bailout in a >> fatal error with a nice description. It never hurts. >> >> ~Robert Widmann >> >>> On Oct 3, 2016, at 6:14 AM, Adrian Zubarev via swift-evolution >>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >>> >>> I know that there is this note in Commonly Rejected Changes >>> <https://github.com/apple/swift-evolution/blob/master/commonly_proposed.md>: >>> >>> Remove support for default: in switch and just use case _:: default is >>> widely used, case _ is too magical, and default is widely precedented in >>> many C family languages. >>> I really like to use the switch instead of if case for pattern matching, >>> just because it’s neat block design. I do not want to remove default from >>> switches because it’s a must have and powerful feature. >>> >>> I’d like to know why switches must be exhaustive. >>> >>> switch someValue { >>> >>> case …: >>> // Do something >>> >>> case …: >>> // Do something else >>> >>> default: >>> () // useless nop; do nothing when no pattern matched >>> } >>> >>> // VS: >>> >>> if case … { >>> >>> } else if case … { >>> >>> } else if case … { >>> >>> } // No need for `else` >>> Can’t we make default optional, or at least on non-enum values? >>> >>> >>> >>> >>> -- >>> Adrian Zubarev >>> Sent with Airmail
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
