[swift-users] Non-escaping closure not allowed to do let initialization?

[Shawn Erickson]

I meant to state otherwise I have to fallback on IUO to make it work
cleanly...

    public func finish() throws -> ([String:String],InputStream) {
        var formHeaders: [String:String]!
        var formStream: InputStream!
        try finish({ (fh, fs, _) in
            formHeaders = fh
            formStream = fs
        })
        return (formHeaders, formStream)
    }

On Thu, Feb 2, 2017 at 12:33 PM Shawn Erickson <shawnce at gmail.com> wrote:

> I attempted the following code which involves passing a closure – one that
> doesn't escape obviously – but the compiler complains that I need to make
> formHeaders and formStream vars.
>
>     public func finish() throws -> ([String:String],InputStream) {
>         let formHeaders: [String:String]
>         let formStream: InputStream
>         try finish({ (fh, fs, _) in
>             formHeaders = fh
>             formStream = fs
>         })
>         return (formHeaders, formStream)
>     }
>
> If I have code like this however the use of let is ok.
>
>     public func finish() throws -> ([String:String],InputStream) {
>         let formHeaders: [String:String]
>         let formStream: InputStream
>         if self.finalized.get() {
>             formHeaders = ["foo":"bar"]
>             //formStream = ...
>         }
>         else {
>             formHeaders = [:]
>             //formStream = ...
>             // or throw something here
>         }
>         return (formHeaders, formStream)
>     }
>
> If the closure is non-escaping and the code as structured the compiler
> should be able to reason about the initialization correctness of those
> lets...? ...or am I missing something?
>
> -Shawn
>
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