[swift-evolution] Proposal: An assignment operator := that ensures nil before assignment.

[Ross O'Brien]

How is this different from the rejected ??= proposal?

On Sat, Feb 27, 2016 at 2:34 PM, Amir Michail via swift-evolution <
swift-evolution at swift.org> wrote:

> Consider the use of “!” in the following:
>
> var x: Int? = 5
>
> x! = 2 // “!” is used to ensure non-nil value before assignment
>
> The idea is to have a similar method for ensuring a nil value.
>
> So instead of writing:
>
> precondition( x == nil )
> x = 3
>
> You could write:
>
> x := 3
>
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