1

Hi, I have probably a strange compiling error for the following code

import Foundation

class BB {
  func process(val: @escaping () -> Void) {}
}

class AA {
  let bb = BB()

  func cc() -> Int? {
    return nil
  }

  func fetch() {
    bb.process { [weak self] in
      guard let self = self else {
        return
      }
      lazy var aa = self.cc

      guard let a = aa() else {
        return
      }
    }
  }
}

Cannot reference invalid declaration 'self' but if I replace lazy var to just let it's gone.

import Foundation

class BB {
  func proccess(val: @escaping () -> Void) {}
}

class AA {
  let bb = BB()

  func cc() -> Int? {
    return nil
  }

  func fetch() {
    bb.proccess { [weak self] in
      guard let self = self else {
        return
      }
      let aa = self.cc()

      guard let a = aa else {
        return
      }
    }
  }
}

Can someone please explain is a bug or if this is correct behavior why?.
I'm using Xcode 13.3.1(Swift 5.6)

2

It's a quirk of lazy var that it's the only kind of instance property initialization that is allowed to reference self. It's not really a good quirk, but I think it hangs around because it is convenient sometimes (and would be source-breaking to remove).

3

This is interesting, and I don't know the answer. If you remove the code that uses the lazy var you get a different error:

error: class declaration cannot close over value 'self' defined in outer scope