[swift-evolution] [idea] errors in properties

Ben Rimmington me at benrimmington.com
Wed Jul 26 00:21:11 CDT 2017

Brent Royal-Gordon has written a draft proposal:


> On 25 Jul 2017, at 21:58, Gor Gyolchanyan via swift-evolution <swift-evolution at swift.org> wrote:
> This sounds like a challenge 🙂 
> But seriously, seems like straight-up implementing the feature and then wondering whether or not the pull request will be merged in or rejected is an unnecessary gamble, which is why swift-evolution exists.
> Haven’t anyone tried to make a proposal for this?
> I’d gladly look into implementing it myself if I new for sure that my efforts wouldn’t be wasted.
>> On Jul 25, 2017, at 11:55 PM, Xiaodi Wu <xiaodi.wu at gmail.com <mailto:xiaodi.wu at gmail.com>> wrote:
>> There have been a number of discussions on the list in this—Google finds a number of these with a search “swift throwing properties site:lists.swift.org <http://lists.swift.org/>”.
>> The “tldr” seems to be that it’s not supported because no one has written code to support it yet.
>> On Tue, Jul 25, 2017 at 15:29 Gor Gyolchanyan via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> I’ll just cut to the chase:
>> Why is throwing from get, set, willSet and didSet disallowed?
>> var login: String {
>> 	willSet throws {
>> 		guard newValue.count > 5 else {
>> 			throw LoginError.loginTooSmall
>> 		}
>> 	}
>> }
>> try login = “JebediahKerman” // totally fine
>> try login = “Bob” // throws `LoginError.loginTooSmall`
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