[swift-evolution] [Pitch] Guard/Catch

[Dave DeLong]

Soroush’s proposal has the idea that maybe we could do multiple blocks for this scenario, like so:

guard try something(), let thing = optionalThing catch {
    // try something() failed
} else {
    // the let-binding failed
}

🤔 Alternatively, what if the “error” captured was optional in this scenario?

guard try something(), let thing = optionalThing catch {
    if let error = error {
        // the try call failed
    } else {
        // the optional binding failed
    }
}

Dave

> On Jul 5, 2017, at 12:00 PM, Jon Shier via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 	I didn’t think I was going to like it but I really do. My only concern, which isn’t really a deal breaker, is what it would look like to chain multiple try and let statement in the same guard. Unless that scenario works well I don’t think you could convince others. i.e. In the case where I have:
> 
> guard try something(), let thing = optionalThing catch { }
> 
> What happens when the let fails? No implicit error?
> 
> 
> 
> Jon
> 
> 
>> On Jul 5, 2017, at 1:30 PM, Soroush Khanlou via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I’d like to propose a guard/catch construct to the language. It would allow code to use throwing functions and handle errors fully, without straying from a happy path. do/catch can be a bit heavy-handed sometimes, and it would be nice to be able to handle throwing functions without committing to all the nesting and ceremony of do/catch.
>> 
>> Full proposal, which discusses all the corner cases and alternatives:
>> https://gist.github.com/khanlou/8bd9c6f46e2b3d94f0e9f037c775f5b9 <https://gist.github.com/khanlou/8bd9c6f46e2b3d94f0e9f037c775f5b9>
>> 
>> Looking forward to feedback!
>> 
>> Soroush
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> 
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