[swift-evolution] Assignment to 'let' constant in defer blocks

[Chris Lattner]

> On Mar 10, 2017, at 9:33 PM, David Sweeris via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Is this a feature or a bug?

Low priority bug IMO.

-Chris


> class Foo {
>     let bar: Int
>     init?(someConditionBasedOnInputData: Bool) {
>         var localBar: Int = 0
>         defer {
>             bar = localBar //Cannot assign to property: 'bar' is a 'let' constant
>         }
>         if someConditionBasedOnInputData {
>             return nil
>         }
>     }
> }
> It’d be handy to be able to do the assignment upfront in a defer block in cases where there’s both a bunch of validation to do on the input data, and no harm from assigning the interim values to the final values when you’re about to return nil anyway.
> 
> - Dave Sweeris
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