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

[Micah Hainline]

I'd prefer the placement at the very end, I do think it would improve readability, especially when taking closures as parameters and returning closures. However, I don't think the value would be worth the cost of breaking existing code. At the least if this were to go forward I would think we'd want both styles to work even if one was preferred or the other was deprecated. 



> On Dec 26, 2016, at 12:41 PM, Derrick Ho via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I personally do not see anything wrong with its current placement.
> 
> It may be there because it was based on an existing cocoa pattern from objective-c
> 
> - (NSString *)bazWithError:(NSError **)error { ... }
> 
> Because objective c could only return one thing, using pointer-to-pointer was needed to deliver more than one.
> 
> When swift came along it became this...
> 
> func baz(error: NSErrorPointer) -> String
> 
> The style felt old-fashioned and was replaced with throw.
> 
> func baz() throws -> String
> 
> 
> The evolution is consistent.  The pattern is familiar.  I think we should keep the placement of throw as it is.
> 
> On Mon, Dec 26, 2016 at 9:38 AM thislooksfun via swift-evolution <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
> 
> 
> 
> // 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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