Functions with wrapped parameters that omit argument labels cannot be referenced.

[JessyCatterwaul]

Supposedly…

If a wrapped parameter omits an argument label, the function can be referenced to take in the projected-value type using $_:

But that's not true. Given:

@propertyWrapper struct PropertyWrapper {
  var wrappedValue: Void { () }
  var projectedValue: Void { () }

  init(wrappedValue: Void) { }
  init(projectedValue: Void) { }
}

func ƒ(@PropertyWrapper _: Void) { }

These compile:

  ƒ(())
  ƒ($_: ())
  _ = ƒ(_:)

This does not:

_ = ƒ($_:) // Cannot find 'ƒ($_:)' in scope