[swift-evolution] [Pitch] Make try? + optional chain flattening work together

[BJ Homer]

I agree that this behavior is annoying. However, wouldn’t it be source-breaking to change this now?

-BJ

> On Jan 12, 2018, at 10:25 AM, Russ Bishop via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Greetings swift-evolution!
> 
> There is currently a disconnect between optional chaining and try? when it comes to optional flattening:
> 
> 
> struct SomeType {
>     func nonThrow() -> SomeType? { return self }
>     func doThrow() throws -> SomeType? { return self }
>     func nonOptional() throws -> SomeType { return self }
> }
> 
> let w = SomeType().nonThrow()?.nonThrow()?.nonThrow()?.nonThrow()
> // w has type SomeType?
> 
> let x = try? SomeType().nonOptional().nonOptional().nonOptional().nonOptional()
> // x has type SomeType?
> 
> let y = try! SomeType().doThrow()?.doThrow()?.doThrow()?.doThrow()
> // y has type SomeType?
> 
> let z = try? SomeType().doThrow()?.doThrow()?.doThrow()?.doThrow()
> // z has type SomeType??
> 
> 
> We get a double-optional only when combining try? and optional-chaining. That is inconvenient and it would be natural to have the compiler do the flattening here.
> 
> 
> If anyone is interested in working on the proposal or implementation please let me know. It would make a nice self-contained task if you're looking to start contributing.
> 
> 
> Russ Bishop
>  Simulator
> 
> 
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