[swift-evolution] Proposal: Improve switch control flow substituting fallthrough with a more safe one

[Jacopo Andrea Giola]

Hi Chris,

well now after some debate in the old thread and the flaws highlighted there I’ve wrote e different proposal and narrowed the changes to only make fallthrough respect the where clause if present and to explicitly state the case where you want to fall.
This I think will improve the safety of the keyword and can further reduce hidden bugs in the keyword usage. The removing of fallthrough is in the title only because with the new behaviour the meaning in not correct anymore.
It can make sense?

- Jacopo

> On 15 Dec 2015, at 22:32, Chris Lattner <clattner at apple.com> wrote:
> 
> 
>> On Dec 15, 2015, at 1:03 AM, Jacopo Andrea Giola <swift-evolution at jacopo.giola.org <mailto:swift-evolution at jacopo.giola.org>> wrote:
>> 
>> Hi Chris,
>> 
>> sorry for bothering you, but during the festivity I finally have some time to work on the formal proposal draft and I’m trying to find where the switch and fallthrough behaviours are defined.
>> Can you point me in the right direction? I want to see if it is feasible and fill the "Detailed design” section of the proposal with something that has some sense and can be used as a reference on how to implement the new keyword if is accepted.
> 
> Are you asking my opinion of the topic?  There were two related things discussed in the thread:
> 
> 1) removing fallthrough: I found the arguments personally unconvincing.  I feel that removing fallthrough would make some important things much harder to express and uglier, potentially leading to buggier code.  I also feel that the behavior of “fallthrough” is obvious even if you’re not familiar with it, so the reasons to remove ++/— and c-style-for don’t apply.
> 
> 2) on adding reswitch: It’s an interesting extension, but very narrow in applicability, and purely syntactic sugar over what we have now.  I don’t see a compelling reason to add it now, given the other higher priority things we need to make happen for swift 3.
> 
> -Chris
> 
> 
>> 
>> Thank you very much.
>> 
>> - Jacopo

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