[swift-evolution] Move placement of 'throws' statement

[Tyler Cloutier]

> On Dec 26, 2016, at 2:55 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> on Mon Dec 26 2016, thislooksfun <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> Hello Swifters,
>> 
>> I've been writing a lot more Swift code recently, and I have found
>> that the default placement of the 'throws' declaration is often
>> confusing, especially to those of us switching from languages where
>> the type of errors thrown is explicitly defined (like Java)
>> 
>> For example,
>> // This is pretty clear, this can throw an error
>> func foo() throws
>> { ... }
>> 
>> // Also pretty clear, this returns a String
>> func bar() -> String
>> { ... }
>> 
>> // Confusing. Does this throw a String? Does it return a String? Does it do both?
>> // I personally keep reading this as 'this can throw a String'
>> func baz() throws -> String
>> 
>> // Equivalent code in Java (not a model, just for clarification of why the above is confusing)
>> String baz() throws StringFormatException
>> I therefore suggest either tweaking the syntax around, or moving, the
>> `throws` keyword to avoid this confusion.
>> 
>> Some ideas I've had:
>> // Add a comma to separate them
>> func baz() throws, -> String
>> 
>> // Move `throws` to the end
>> func baz() -> String throws
> 
> I agree that reads much better.

func baz() -> (String | throws)
func baz() -> (String | throws: BazError)
let x: (_ a: Int) ->  (throws | (_ b: Float) -> (throws | Double))

Now where getting somewhere. Somewhere weird, to be sure… but somewhere.


> 
>> // Change it to a prefix modifier (like `mutating`)
>> throwing func baz() -> String
>> I'm still not sold on any of the above syntaxes, but I would love to hear your feedback.
>> 
>> This would affect existing code, but it would be a fairly small change
>> that would result in very large readability improvements, especially
>> for newcomers, and especially for those coming for a language such as
>> Java.
>> 
>> -thislooksfun (tlf)
>> 
>> _______________________________________________
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>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
> 
> -- 
> -Dave
> 
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