Pre-pitch: remove the implicit initialization of Optional variables

[Nevin]

@jrose

Double initialization is not a bug, it’s a feature. :-) That is, the behavior you’re describing was deliberate, if not always what people want.

The acceptance notes for SE–0242 might suggest otherwise:

@tkremenek

The proposal review also discussed an interesting behavioral quirk with initial values and side-effects, for example:

struct Foo {
  var i: Int = getDefaultValue()
}

struct Bar {
  var i: Int = getDefaultValue()
  init(i: Int) { self.i = i }
}

let x = Foo(i: 1)  // No side effects
let y = Bar(i: 1)  // Yes side effects

The Core Team felt that this was a bug in the compiler's implementation of initializers. The failure here is that Bar calls the side effect, and it is not the right behavior. Addressing this would likely require an evolution proposal, or at least an assessment of whether or not fixing this would break existing code.