[swift-evolution] [Review] SE-0155: Normalize Enum Case Representation

[Christopher Kornher]

> On Feb 20, 2017, at 12:31 PM, Christopher Kornher via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> 
>> On Feb 18, 2017, at 6:16 AM, David Rönnqvist via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> On 18 Feb 2017, at 09:30, Slava Pestov via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>>> +1, two small questions:
>>> 
>>> - If two cases have the same base name but different full names, will matching on the base name match both cases, or will it be an error?
>> 
>> I feel that it would be safer if it was an error. If the developer intends to match both cases, requiring both explicitly is a (slight) inconvenience but it's also very clear about what's going to match. 
> 
> I disagree. It is simple enough to use different base names if you don’t want the cases to match. An example of why it should not be an error: I intend to for errors with same base names to be handled in the same way and I don’t want to enumerate all the similar cases and change code every time I add a new way to construct an error. I understand that other people want the equivalent of function overloading. Code that needs to access values must deal with unique cases, so type safety is assured in any case.
> 
> Java enums have arguments and match on “base names” (they are quite different, but the precedent exists) and I don’t think that matching on the base name would be confusing. I also do not believe that it is worth adding this feature if all cases are completely unique.The pain of forcing a (probably small) subset of developers to use unique names is preferable to complicating the language for no functional benefit, in my opinion.

A possible compromise: specify that all base names should be matched with a new keyword (or?) Here the keyword ```all``` is used to match all base names.

```
enum MyError : Error
{
    case e( a: String )
    case e( a: Int )
}

func handleError( error: MyError )
{
    switch error {
    case all .e :
        break
    }
}
```

> 
> 
>> 
>>> - What are the memory layout optimizations described here? From a first glance this looks purely syntactic.
>>> 
>>> Slava
>>> 
>>>> On Feb 17, 2017, at 7:26 PM, John McCall via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> 
>>>> Hello Swift community,
>>>> 
>>>> The review of "SE-0155: Normalize Enum Case Representation" begins now and runs through next Friday, February 26th. The proposal is available here:
>>>> 	https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md <https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md>
>>>> 
>>>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>>>> 	https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>>>> 
>>>> 	Proposal link: https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md <https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md>
>>>> 
>>>> 	Reply text
>>>> 
>>>> 	Other replies
>>>> 
>>>> What goes into a review?
>>>> 
>>>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>>>> 
>>>> 	• What is your evaluation of the proposal?
>>>> 	• Is the problem being addressed significant enough to warrant a change to Swift?
>>>> 	• Does this proposal fit well with the feel and direction of Swift?
>>>> 	• If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
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>>>> 
>>>> More information about the Swift evolution process is available at https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
>>>> 
>>>> Thank you,
>>>> 
>>>> John McCall
>>>> Review Manager
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