Optional `var` properties should default to `nil` for non-public initializers

[gohanlon]

Description

MemberwiseInit's behavior doesn't match Swift's memberwise init:

struct S {
  var v: String?
}
_ = S()

@MemberwiseInit
struct M {
  var v: String?
}
_ = M()  // 🛑 Compiler error: Missing argument for parameter 'v' in call

MemberwiseInit provides this initializer:

internal init(
  v: String
) {
  self.v = v
}

but, to match Swift's memberwise init, MemberwiseInit should provide:

internal init(
  v: String? = nil
) {
  self.v = v
}

(Thanks, @AndreiChenchik!)

Checklist

• [X] If possible, I've reproduced the issue using the main branch of this package.
• [X] This issue hasn't been addressed in an existing GitHub issue or discussion.

swift-memberwise-init-macro version information

0.1.0