[swift-evolution] [Proposal] Enums with stored properties

[Sean Heber]

> With the improved syntax, this could look something like this instead:
> 
> enum FileError: Error, LocalizedError {
>     var url: URL { get }
>     
>     case notFound(url: URL) {
>         errorDescription = "Could not access the file \(url.lastPathComponent) because it could not be found."
>         failureReason = "The file \(url.lastPathComponent) could not be found."
>         recoverySuggestion = "Please locate the correct file and try again."
>         helpAnchor = "notFound"
>         url = url
>     }
>     
>     case accessDenied(url: URL) {
>         errorDescription = "Could not access the file \(url.lastPathComponent) because access was denied."
>         failureReason = "We do not have permission to view the file \(url.lastPathComponent)"
>         recoverySuggestion = "You can change the file's permissions using the Finder's Get Info window."
>         helpAnchor = "accessDenied"
>         url = url
>     }
>     
>     case incorrectFormat(url: URL) {
>         errorDescription = "Could not access the file \(url.lastPathComponent) because it was not in the expected format."
>         failureReason = "The file \(url.lastPathComponent) was not in the expected format."
>         recoverySuggestion = "The file may have become corrupt."
>         helpAnchor = "incorrectFormat"
>         url = url
>     }
>     
>     case ioError(url: URL) {
>         errorDescription = "Could not access the file \(url.lastPathComponent) because an I/O error occurred."
>         failureReason = "An I/O error occurred while accessing the file \(url.lastPathComponent)."
>         recoverySuggestion = "Dear Lord, the hard drive may be failing."
>         helpAnchor = "ioError"
>         url = url
>     }
>     
>     // ... etc ...
> }
> 
> I don’t think it can be denied that the second is orders of magnitude easier to read and comprehend.
> 
> Charles

I’m 100% in favor of something approaching this syntax where the case-specific values are all grouped by the case and not the other way around.

l8r
Sean