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

[Amir Michail]

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